Abstract The Leadshine L7 series AC servo drives are crucial components in the field of industrial automation. The startup display sequence reflects the device’s initialization status and operational readiness. This paper provides an in-depth analysis of the phenomenon where users observe a brief display of “1.d002” followed by a switch to “00ST,” indicating a normal initialization process. By interpreting the manual, safety precautions, and incorporating online resources from similar EL7 series, it explores the meanings of display codes, diagnostic methods, potential causes, and optimization strategies, aiming to offer comprehensive guidance to engineers and technicians.
Introduction In modern industrial automation systems, servo drives play a pivotal role. The Leadshine L7 series AC servo drives utilize the latest DSP from Texas Instruments (TI), featuring high integration and reliability. Users often encounter startup display issues, such as the display showing “1.d002” briefly after power-on, followed by a switch to “00ST.” This paper centers on this phenomenon, conducting a systematic analysis by combining excerpts from the user manual and online resources, aiming to assist users in understanding the technical implications of the display sequence and providing practical diagnostic steps.
Servo Drive Fundamentals
Basic Principles
Servo drives drive servo motors to achieve precise motion by receiving command signals from an upper-level controller. The fundamental principles include triple-loop control (position loop, speed loop, and current loop), with PID algorithms at the core.
L7 Series Characteristics
The L7 series belongs to AC servo drives, supporting 220VAC input and a wide power range. The manual emphasizes that improper operation can lead to severe consequences, and users must adhere to safety precautions.
Key Components and Initialization
The key components of a servo system include the drive, motor, and encoder. The drive integrates a DSP processor, and the initialization process involves self-tests, parameter loading, and status monitoring.
Display Panel Basics
The display panel employs a seven-segment LED digital tube, supporting status display, parameter settings, and alarm prompts. Understanding these codes is crucial for diagnosing device status.
Control Modes and Parameter Settings
Servo drives offer control modes including position, speed, and torque modes. Parameter settings are achieved through panel buttons or MotionStudio software.
Safety Guidelines
The manual stresses that product storage and transportation must comply with environmental conditions, and user modifications will void the warranty.
Overview of the L7 Series
Product Features and Updates
The Leadshine L7 series is a fully digital AC servo drive, utilizing TI DSP, supporting stiffness tables, inertia identification, and vibration suppression. The version has evolved from V1.00 to V2.10 with continuous updates.
Application Areas and Manual Structure
The L7 series finds wide applications in PLC control, robotic arms, and other fields. The manual structure covers the preface, safety matters, specifications, installation, wiring, commissioning, and maintenance.
Wiring and Version Descriptions
Wiring includes power, motor, encoder, and I/O ports. The version description indicates program compatibility and content updates.
Display Panel in Detail
Operation Interface and Key Functions
The L7 drive’s operation interface consists of a 6-digit LED digital tube and 5 keys for status display and parameter settings.
Initialization and Monitoring Mode Codes
Upon power-on, the panel first displays initialization codes. “1.d002” may be a custom or transient display, and switching to “00ST” indicates a standby state. Monitoring mode codes include position deviation, motor speed, etc.
Alarm Code Interpretation
Alarm codes start with “Er,” and the absence of “Er” indicates normal operation.
Diagnostic Analysis
Core Phenomenon Interpretation
The display showing “1.d002” briefly followed by a switch to “00ST” is a normal sequence. The initialization process includes self-tests and parameter loading.
Potential Causes Explored
Potential causes include normal boot-up, configuration influences, and external factors.
Diagnostic Steps and Methods
Diagnostic steps include checking the display history, software verification, and factory reset.
Troubleshooting
Non-Normal Situation Exclusion Methods
If non-normal, exclusion methods include power supply checks, wiring verification, parameter resets, and software tuning.
Common Faults and Solutions
Common faults such as overcurrent and overload are unrelated to the display sequence.
Applications and Optimization
Case Studies: CNC Machine Tools and Robotic Arms
Case 1: A CNC machine tool uses the L7 to control axes, and a normal startup sequence ensures precision. Case 2: A robotic arm in bus mode uses EtherCAT synchronization to avoid delays.
Optimization Strategies and Future Trends
Optimization strategies include adjusting control modes and vibration suppression. Future trends involve integrating AI tuning.
Conclusion The transition from “1.d002” to “00ST” indicates a normal state. Mastering diagnostic methods can enhance application efficiency. It is recommended to refer to the manual and technical support to ensure stable system operation.
I. Introduction: When the Brain of the Drive Crashes
The Mitsubishi FREQROL-A700 inverter series is renowned for its high-performance vector control, stable communication capabilities, and comprehensive protection functions. It is widely used in CNC machines, plastic molding equipment, air compressors, hoists, and a variety of industrial automation lines.
However, when the display shows “E.7” or “E.CPU”, the inverter immediately halts output, and the entire system comes to a standstill. This is often referred to by technicians as a “brain crash,” as it indicates a critical failure of the inverter’s central processing unit (CPU).
Among all protection codes, E.7 is one of the most severe. It typically signals that internal communication between control units has failed, logic processes have become unstable, or the CPU hardware itself has malfunctioned. This article offers a comprehensive technical exploration of the E.7 (CPU Error) fault — its causes, diagnostic methods, hardware implications, repair solutions, and preventive measures — supported by real industrial case studies.
II. Understanding the Fault and System Logic
According to the FR-A700 User Manual (page 397):
E.6 / E.7 / E.CPU – CPU Error When an internal CPU communication error occurs, the inverter stops output. Inspection Point: Check if there are devices around the inverter that generate strong electrical noise. Measure: If no external interference is found, contact the supplier or Mitsubishi service center.
This indicates that E.7 is a system-level protection event. The inverter’s internal logic continuously monitors communication between the main CPU, gate driver interface, and memory/control buses. If any communication timeout or checksum failure occurs, the CPU triggers a protective shutdown to prevent unpredictable IGBT switching or hardware damage.
The main CPU fault logic in the FR-A700 involves:
Abnormal communication between the main processor and gate drive circuits.
Data corruption or response failure in EEPROM, ADC, or communication ICs.
Watchdog timer reset caused by logic hang or power fluctuation.
When the watchdog detects that the CPU fails to respond within its monitoring period, the system declares a “CPU Communication Error” and displays E.7.
III. Technical Causes of the CPU Error
The E.7 fault generally stems from three major categories of issues:
Electromagnetic interference (EMI)
Power supply instability
Internal control board failure
1. Electromagnetic Interference (EMI)
Industrial sites are rich in high-frequency noise sources — welding machines, large contactors, induction heaters, and switching power supplies. These generate voltage spikes and transient electromagnetic waves that couple into the control board’s circuits, disturbing the CPU clock or data bus.
Typical EMI sources include:
Arc welders or high-frequency induction furnaces
Contactors or solenoid valves switching nearby
Control signal lines routed in parallel with power cables
Improper or floating grounding systems
In such cases, E.7 may occur intermittently, often clearing after power cycling — a sign that transient interference is affecting the CPU.
Technical Recommendations:
Separate control wiring from power cables (minimum 10 cm apart).
Use twisted shielded cables for control and communication lines.
Ground all shields at one single point only.
Install proper EMI filters and ferrite cores on input lines.
2. Power Supply Fluctuations or Grounding Issues
The FR-A700 series contains multiple voltage rails — DC bus (≈540 VDC), control voltage (24 VDC), and logic voltage (5 VDC). When any of these experience transient drops due to unstable input voltage, aging capacitors, or poor grounding, the CPU watchdog may trigger an internal reset, leading to an E.7 CPU Error.
Typical symptoms:
E.7 appears immediately upon power-up
Random alternation between E.6 and E.7
Display flickering or panel freezing
Diagnostic Points:
Measure three-phase input balance and verify stable voltage.
Check DC bus voltage ripple — excessive ripple suggests degraded capacitors.
Measure 24V and 5V supply rails; ensure no drop below tolerance.
Inspect the grounding system — avoid shared return paths with external PLCs or IO devices.
3. Hardware Failure on Control or Power Board
If E.7 persists after confirming stable power and minimal EMI, the most likely cause is a hardware fault.
Common hardware-related sources:
Damaged main CPU (e.g., Renesas or Mitsubishi custom MCU)
Failed EEPROM or memory IC communication
Broken optocouplers (HCPL-2631, etc.) between logic and driver circuits
Poor connection between control board and power board
Feedback interference caused by a shorted IGBT module
Observable signs:
Instant E.7 alarm at power-up
Unable to reset via panel or RES signal
FR-Configurator2 communication fails
No clock signal detected on the CPU oscillator
In this situation, replacing the control PCB or even the entire inverter is often the most efficient solution.
IV. Step-by-Step Diagnostic Procedure
A systematic diagnostic process can help quickly isolate the E.7 cause.
Step 1: Record and Observe
Note when the error occurs (during start, stop, idle, or communication).
Observe whether the fault happens after brief power loss.
Check ambient temperature (CPU overheating can cause instability).
Step 2: Insulation and Ground Testing
After disconnecting power and waiting at least 10 minutes, measure insulation resistance (>5 MΩ) between main terminals and ground.
Ensure no short between control circuits and main circuit.
Step 3: Check for Interference and Grounding Issues
Verify that PE grounding resistance is below 10 Ω.
Ensure all power cables are symmetrical (balanced three-phase).
Avoid “loop grounds” by ensuring star-point grounding topology.
For RS-485 or CC-Link communication, ground the shield at one end only.
Step 4: Monitor Power Rails
Use an oscilloscope to monitor 24V and 5V supplies; ensure minimal ripple (<100 mV).
Confirm the DC bus is steady without oscillation when idle.
Step 5: Module-Level Inspection
Re-seat the operation panel and connectors between boards.
Examine ribbon cables for oxidation or loose pins.
Swap with a known-good control board if available.
If error persists → replace power board or complete drive.
V. Repair and Replacement Strategies
1. Component-Level Control Board Repair
Qualified service technicians can:
Verify CPU clock oscillator output (16–20 MHz typical).
Check watchdog timer pulse (ICs like 74HC123).
Replace EEPROM, voltage regulators, or capacitors.
Re-solder cracked joints and clean carbon residue.
Add low-ESR capacitors (e.g., 47 µF × 2) near CPU power pins to enhance filtering.
2. Inverter Replacement and Parameter Recovery
When the board is irreparable:
Use FR-Configurator2 to back up parameters before removing the unit.
Install the new inverter, then restore parameters via copy function (Pr.990–Pr.999).
Run auto-tuning (Pr.71, Pr.80–Pr.84) to recalibrate motor characteristics.
3. Environmental Hardening
For long-term stability:
Add EMI filters or isolation transformers on input side.
Install surge absorbers (MOVs) between R/S/T lines.
Route control and power cables separately.
Maintain good cabinet ventilation and cleanliness.
VI. Case Study: CPU Error in Injection Molding Machine
An FR-A740-22K-CHT inverter was used as the main drive in a plastic injection molding machine. The unit displayed E.7 intermittently; resetting restored operation temporarily.
Investigation findings:
Three inverters were installed side-by-side in the same panel.
Control signal cables ran parallel to motor leads.
Ground connections were multi-pointed, creating loops.
Heavy dust on control board and fan filter.
Corrective actions:
Re-routed control cables with shielded twisted pairs.
Implemented star-point grounding.
Added 100 µF capacitor to 5V rail on control board for ripple suppression.
Cleaned dust and re-seated connectors.
After these measures, the machine ran for 72 hours continuously without reoccurrence. Conclusion: E.7 was caused by EMI-induced communication loss rather than true CPU failure.
VII. Relationship Between Related Error Codes
Code
Description
Meaning
Correlation
E.6
CPU Communication Error A
Communication loss in main logic channel
Often co-occurs with E.7
E.7
CPU Communication Error B
Internal bus or logic timing fault
May escalate to E.CPU
E.CPU
CPU Hardware Fault
CPU self-check failure or watchdog timeout
Severe or persistent E.6/E.7
If E.6, E.7, and E.CPU alternate rapidly, it typically indicates either a logic power fault or crystal oscillator failure.
VIII. Preventive Engineering Practices
1. During Electrical Design
Provide dedicated grounding bars (no shared returns).
Use separate grounding cables for each inverter.
Add RC snubber circuits or line filters on power input.
Use crimp terminals for all wiring to prevent loose contacts.
2. During Installation and Commissioning
Test motor insulation before wiring to inverter.
Avoid long, unshielded communication lines.
Use optical isolation modules when interfacing PLCs.
3. During Routine Maintenance
Clean cooling channels and fans every 6 months.
Check fan bearings and noise levels.
Measure DC bus capacitor ESR annually.
Use heaters or dehumidifiers in damp environments.
4. Backup and Record Management
Regularly back up parameters via FR-Configurator2 or PU unit.
After replacing the control board, verify calibration parameters.
For aging units, perform preventive replacement of capacitors and relays.
IX. Technical Insights and Summary
The E.7 fault in the Mitsubishi FR-A700 series is a CPU communication error — a high-level protection mechanism that prevents erratic operation when the internal logic loses synchronization. It does not relate to mechanical load or overcurrent events, but rather to the integrity of digital control.
Based on field experience, E.7 can be categorized into three scenarios:
Type
Root Cause
Solution
Intermittent
Electrical noise or unstable power
Improve grounding and filtering
Recurrent
Loose connectors, aged components
Maintenance and board cleaning
Persistent
Damaged CPU or control board
Replace control board or full unit
Following the logical troubleshooting flow — external causes → power check → control circuit diagnosis — enables engineers to identify the root problem quickly and avoid unnecessary replacements.
In preventive terms, a robust EMC design and proper grounding layout remain the most effective strategies to eliminate CPU communication errors in high-frequency drive systems.
X. Practical Recommendations
For environments with frequent E.7 errors, consider using a 1:1 isolation transformer (2 kVA or above) for the inverter’s control supply.
In high-temperature cabinets (>45°C), add external forced-air cooling.
For long-distance communication, use optical fiber isolation modules instead of RS-485 copper lines.
For multi-inverter systems, use independent control power supplies for each unit.
Conclusion
The E.7 CPU Error is not simply a nuisance fault — it is an intelligent self-protection feature designed to prevent catastrophic failure in the Mitsubishi FR-A700 inverter series. Understanding its electrical, logical, and environmental causes allows engineers to perform accurate diagnostics, avoid misjudgment, and reduce downtime.
In today’s automation landscape, where system reliability and electromagnetic compatibility (EMC) are paramount, addressing E.7 is not merely about fixing an error — it’s about building resilience into every layer of the control system.
The EST900 series inverter from Yiste, as a high-performance vector inverter, is widely applied in the control and speed regulation of three-phase asynchronous motors. This article, based on the official manual, will elaborate in detail on its operation panel functions, parameter setting methods, external terminal control and speed regulation implementation, as well as handling measures for common fault codes, helping users quickly master the usage skills.
I. Introduction to Operation Panel Functions and Parameter Settings
(A) Overview of Operation Panel Functions
The EST900 series inverter comes standard with an LED operation panel, which offers a variety of functions:
Status Monitoring: It can display key information such as operating frequency, current, voltage, and fault codes in real time.
Parameter Setting: It supports viewing and modifying functional parameters.
Operation Control: Control commands such as start, stop, and forward/reverse rotation can be executed through the panel.
Indicator Lights: It is equipped with indicator lights including RUN (operation), LOCAL/REMOT (control source), FWD/REV (direction), and TUNE/TC (tuning/torque/fault), which visually reflect the equipment status.
(B) Factory Parameter Settings
During debugging or when parameters are in disarray, a factory reset operation can be performed:
Steps:
Enter the FP – 01 parameter.
Set it to 1 (restore factory parameters, excluding motor parameters).
Press the ENTER key to confirm.
Wait for the display to restore, indicating parameter initialization is complete.
Notes:
FP – 01 = 2 can clear fault records and other information.
FP – 01 = 4 can back up the current parameters.
FP – 01 = 501 can restore the backed-up parameters.
(C) Password Setting and Clearing
To prevent misoperation, a user password can be set:
Setting a Password:
Enter FP – 00 and set it to a non-zero value (e.g., 1234).
After exiting, the password needs to be entered when accessing parameters again.
Clearing a Password:
Set FP – 00 to 0.
(D) Parameter Access Restrictions
Parameter access can be restricted in the following ways:
Parameter Group Display Control:
Set the FP – 02 parameter to control whether Group A and Group U parameters are displayed.
For example, setting it to “11” can hide some parameter groups to prevent mismodification.
Prohibition of Modification during Operation:
Some parameters marked with “★” cannot be modified during operation and need to be set after shutdown.
II. External Terminal Forward/Reverse Rotation Control and Potentiometer Speed Regulation
(A) External Terminal Forward/Reverse Rotation Control
Note: If a three-wire control system is used, set F4 – 11 = 2 or 3 and cooperate with other DI terminals.
(B) External Potentiometer Speed Regulation
Wiring Terminals:
+10V: Positive pole of potentiometer power supply
GND: Negative pole of potentiometer power supply
A11: Analog voltage input (0 – 10V)
Parameter Settings: | Parameter Code | Name | Setting Value | Description | | —- | —- | —- | —- | | F0 – 03 | Main Frequency Command Selection | 2 | A11 | | F4 – 13~F4 – 16 | A11 Curve Settings | Adjust according to actual conditions | Minimum/maximum input corresponds to frequency |
Tip: It is recommended that the potentiometer resistance be between 1kΩ and 5kΩ to ensure that the current does not exceed 10mA.
III. Common Fault Codes and Handling Methods
The EST900 series inverter has a comprehensive fault diagnosis function. The following are common faults and their handling methods:
(A) Overcurrent Faults
Fault Code
Name
Possible Causes
Handling Measures
Err02
Acceleration Overcurrent
Motor short circuit, too short acceleration time
Check motor insulation, increase acceleration time
Err03
Deceleration Overcurrent
Short deceleration time, large load inertia
Increase deceleration time, install a braking resistor
Err04
Constant-speed Overcurrent
Load mutation, mismatched motor parameters
Check the load, perform motor tuning again
(B) Overvoltage Faults
Fault Code
Name
Possible Causes
Handling Measures
Err05
Acceleration Overvoltage
High input voltage, external force during acceleration
Check power supply voltage, enable overvoltage suppression
Err06
Deceleration Overvoltage
Short deceleration time, energy feedback
Increase deceleration time, install a braking unit
Err07
Constant-speed Overvoltage
External force dragging during operation
Check the mechanical system, enable overvoltage suppression
(C) Other Common Faults
Fault Code
Name
Possible Causes
Handling Measures
Err09
Undervoltage Fault
Low power supply voltage, rectifier bridge fault
Check the power supply, measure the bus voltage
Err10
Inverter Overload
Excessive load, undersized selection
Check the load, replace with a higher-power inverter
Err11
Motor Overload
Excessive motor load, improper protection parameter setting
Adjust the F9 – 01 motor overload gain
Err14
Module Overheating
Poor heat dissipation, fan fault
Clean the air duct, replace the fan
Err16
Communication Fault
Wiring error, improper parameter setting
Check the communication line, set FD group parameters
(D) Fault Reset Methods
Press the STOP/RESET key on the panel.
Set a DI terminal to the “Fault Reset” function (F4 – xx = 9).
Write “2000H = 7” through communication.
Power off and restart (wait for more than 10 minutes).
IV. Conclusion
The Yiste EST900 series inverter is powerful and flexible in operation, capable of adapting to various industrial scenarios. Through the introduction in this article, users can master the following key contents:
Basic usage methods of the operation panel and parameter setting skills.
How to control and regulate the speed of the motor using external terminals and a potentiometer.
Diagnostic ideas and handling skills for common faults.
Effective use of password management and parameter protection mechanisms. During actual use, it is recommended that users strictly follow the manual specifications for wiring and parameter setting, and regularly carry out maintenance work to ensure the long-term stable operation of the equipment.
In industrial automation systems, frequency inverters are the key components for controlling motor speed and torque. The operational stability of an inverter directly determines the reliability of an entire production line. Among numerous industrial drive products, the Emerson EV2000 series is well recognized for its robust performance, precise vector control, and adaptability to a wide range of applications — from pumps and fans to textile machines and conveyors.
However, during field operation or long-term use, some users may encounter a display message reading “P.oFF” on the inverter’s LED panel. At first glance, this may look like a severe fault such as a power module failure or control board defect. In reality, “P.oFF” is not a typical fault alarm, but rather a protective shutdown state known as “Undervoltage Lockout (LU).”
This article provides a comprehensive technical analysis of the P.oFF condition in the Emerson EV2000 inverter. It integrates official documentation, field diagnostic data, and maintenance experience to explain its causes, triggering mechanism, troubleshooting methods, and preventive measures.
2. Technical Definition of P.oFF
According to the official EV2000 User Manual:
“When the DC bus voltage drops below the undervoltage threshold, the inverter outputs a protection signal and displays ‘P.oFF’ on the LED panel.”
This statement reveals the essence of the fault: P.oFF occurs when the inverter’s internal DC bus voltage (DC link voltage) falls below a safe limit.
Normally, the rectifier circuit inside the EV2000 converts three-phase AC power (380V ±10%) into DC voltage of approximately 540–620 VDC. When the input power drops, the rectifier is damaged, the DC bus capacitors age, or the braking unit malfunctions, the DC voltage may fall below the predefined undervoltage threshold (around 300 VDC). At that point, the inverter automatically enters a protective lockout to prevent unstable operation or component damage.
It is important to note that unlike “E” code faults (such as E001 – overcurrent, E002 – overvoltage), P.oFF does not trigger a trip alarm. Instead, the inverter temporarily disables output until the voltage returns to normal.
3. Electrical Mechanism Behind the P.oFF State
To fully understand this phenomenon, we must look into the EV2000’s main power structure.
3.1 Composition of the Main Circuit
The inverter’s main power path includes the following key components:
Input terminals (R, S, T): three-phase AC supply
Rectifier bridge module: converts AC to DC
DC bus capacitors: stabilize and filter DC voltage
Braking unit and resistor: absorb regenerative energy from motor deceleration
IGBT inverter bridge: converts DC back into PWM-controlled AC output
3.2 How Undervoltage Lockout Is Triggered
The control board constantly monitors the DC bus voltage. When it detects a voltage lower than the threshold (typically around 300–320 VDC), it executes the following logic sequence:
Disables IGBT outputs — halting motor operation
Displays “P.oFF” on the panel
Waits in standby mode until the DC bus recovers above the normal level (typically >380 VDC)
This mechanism is a preventive protection system designed to shield the inverter from grid voltage sags, capacitor discharges, or transient faults. Thus, P.oFF is not an error; it is an intentional safety lock.
4. Root Causes of the P.oFF Condition
From field experience and manual analysis, the following are the most common reasons for P.oFF to appear.
(1) Input Power Problems
Voltage imbalance between the three input phases (>3%)
Mains voltage below 320V AC or fluctuating severely
Loose power terminals or poor contact
Excessive line voltage drop due to long cable runs
These account for nearly half of all P.oFF cases and are primarily related to unstable supply power.
(2) Faulty Rectifier Module
A damaged or open diode inside the rectifier bridge reduces the DC bus voltage, often accompanied by audible hum or irregular current flow.
(3) Aged or Leaky DC Capacitors
Over time, electrolytic capacitors lose capacitance and their internal ESR increases. This weakens their ability to smooth the DC voltage, resulting in a temporary drop when load or braking energy fluctuates — enough to trigger an undervoltage lock.
In units running for 3–5 years, this is one of the most frequent root causes.
(4) Braking Circuit Malfunction
A shorted braking unit or resistor constantly discharges the DC bus, causing the voltage to collapse. To verify, disconnect the braking circuit and power on again — if P.oFF disappears, the issue lies in that circuit.
(5) Momentary Power Interruptions
Factories with welding machines, compressors, or heavy inductive loads can experience grid sags. If the inverter’s “Ride-through” (instantaneous power-loss recovery) function is disabled, any short voltage dip may cause P.oFF.
5. Systematic Troubleshooting Process
To effectively diagnose and repair the P.oFF issue, engineers can follow a step-by-step workflow:
Step 1 – Observe the Symptom
Panel displays “P.oFF”
No “E” fault code is present
Motor stops automatically
After a few minutes, the inverter may restart on its own
If these conditions match, the inverter is in undervoltage lockout mode.
Step 2 – Measure Input Power
Use a multimeter to measure R–S–T line voltages:
Normal range: 380–440 V
Below 360 V or phase difference >10 V → adjust power source or connections
Step 3 – Measure DC Bus Voltage
Check voltage across (+) and (–) terminals:
Normal: 540–620 VDC
Below 300 VDC → rectifier or capacitor failure
Step 4 – Isolate the Braking Circuit
Disconnect the braking resistor/unit and test again. If the problem disappears, replace or repair the braking components.
Step 5 – Test the DC Capacitors
After power-off, measure capacitance and discharge rate:
If voltage drops to zero within a few seconds, leakage is severe
Replace if measured capacitance is <70% of rated value
Step 6 – Verify Control Power
Check auxiliary voltages (P24, +10V, +5V). Low control supply may cause false P.oFF detection.
6. Repair and Recovery Procedures
Once the root cause has been identified, proceed with the following repair actions:
Stabilize Power Supply
Re-tighten input terminals
Ensure voltage balance across all three phases
Install an AC reactor or voltage stabilizer if necessary
Replace Faulty Components
Replace aged electrolytic capacitors as a set
Replace damaged rectifier modules with same-rated units
Inspect Braking Circuit
Measure P–PR resistance for shorts
Ensure thermal relay contacts (TH1, TH2) are functioning
Enable Ride-through Function The EV2000 allows short-duration undervoltage ride-through; enabling this can prevent false P.oFF triggers caused by brief voltage dips.
Recommission and Verify
Power up and observe DC voltage stability
Run at light load for 10 minutes, then gradually increase load
Once the display shows “RDY”, the inverter is ready for normal operation
7. Preventive and Optimization Measures
To avoid recurring undervoltage lockouts, adopt the following best practices:
7.1 Power-Side Protection
Use proper circuit breakers or fuses rated for inverter service
Add a DC reactor for harmonic suppression and voltage stabilization
Use thicker power cables if installation distance is long
7.2 Environmental Control
Maintain cabinet temperature below 40°C
Ensure clean airflow; avoid dust, oil, or moisture buildup
Regularly clean cooling fans and filters
7.3 Periodic Maintenance
Measure DC bus voltage and capacitor health yearly
Replace capacitors after ~3 years of continuous operation
Test rectifier module every 5 years or after heavy load operation
7.4 Parameter Optimization
Set appropriate acceleration/deceleration times to avoid current spikes
Enable AVR (Automatic Voltage Regulation) and Current Limit functions
Review output terminal settings in parameter group F7 to prevent incorrect logic assignments
8. Case Study: Intermittent P.oFF on a 22kW Fan Drive
Background: A 22kW EV2000 inverter controlling a centrifugal fan exhibited intermittent P.oFF shutdowns after six months of operation.
Symptoms:
Occurred around 45 Hz operation
The inverter automatically recovered after a few minutes
Mains voltage appeared normal
Diagnosis:
DC bus voltage fluctuated between 520–550V with periodic dips
Two electrolytic capacitors found bulging and degraded
Replaced capacitors → inverter operated normally
Conclusion: The failure was caused by aged capacitors reducing DC storage capacity, resulting in transient undervoltage. This is a classic “aging-induced P.oFF” scenario.
9. Conclusion
The P.oFF message on Emerson EV2000 inverters is not a random or critical failure, but a designed protective feature to safeguard the drive system when DC bus voltage drops abnormally.
Understanding its mechanism helps engineers correctly differentiate between true hardware faults and temporary protective lockouts. By following a structured diagnostic approach — from input power verification to capacitor and braking circuit inspection — technicians can quickly restore normal operation.
Furthermore, implementing preventive maintenance and enabling built-in functions such as ride-through and AVR can significantly enhance long-term reliability.
As the design philosophy of Emerson EV2000 suggests:
“Reliability is not accidental — it begins with every small detail of protection.”
The TSI VelociCalc 9565 series multifunction air velocity meters, manufactured by TSI Incorporated (USA), are among the most recognized instruments for ventilation testing and cleanroom airflow diagnostics. Their modular design allows the main unit to connect to a variety of intelligent probes through a standard 7-pin Mini-DIN interface, enabling simultaneous measurements of air velocity, airflow, temperature, humidity, CO, CO₂, VOC, and differential pressure.
This article focuses on a specific configuration:
Main unit: TSI 9565-P-NB, a multifunction meter equipped with a differential-pressure sensor (the “-NB” suffix indicates no Bluetooth).
Probe: TSI 964 hot-film probe for air velocity, temperature, and relative humidity.
Together they provide comprehensive readings of velocity, volumetric flow, temperature, humidity, and static/differential pressure, widely used in:
Fume-hood face-velocity tests;
Cleanroom laminar-flow verification;
HVAC air-balancing and commissioning;
Energy-efficiency assessments of ventilation systems.
2. Working Principle and Structural Overview
2.1 Hot-film anemometry
The 964 probe employs a constant-temperature hot-film anemometer. Its sensing element is a precision platinum film that is electrically heated above ambient temperature.
When air passes over the sensor, convective cooling occurs;
The electronic bridge circuit maintains a fixed temperature difference ΔT;
The current required to maintain ΔT is proportional to the square of air velocity;
The resulting signal is linearized and temperature-compensated to yield the velocity reading (m/s).
The probe also houses a temperature and humidity module, ensuring density compensation and stable performance over a wide range of conditions.
2.2 Differential-pressure module
The 9565-P-NB main unit integrates a ±15 in H₂O (±3735 Pa) differential-pressure sensor. Through the positive (+) and negative (–) ports, the meter can measure static or differential pressure and compute velocity using a Pitot tube. Accuracy is specified as ±1 % of reading ±1 Pa.
2.3 Probe-to-main-unit interface
The 7-pin Mini-DIN connector at the base of the instrument provides:
+5 VDC power to the probe;
Analog signal inputs (velocity, temperature, humidity);
A digital line for probe identification and calibration coefficients.
Once connected, the main unit automatically reads the probe’s ID EEPROM, displays its model, and activates relevant measurement menus. If this recognition fails, the instrument shows “Probe Error” and all velocity-related readings remain at 0.00 m/s.
3. Normal Operation Guidelines
3.1 Power-up and warm-up
According to the manual (Chapter 3), the instrument should warm up for about five minutes after power-on before performing pressure zeroing. This stabilizes the internal sensors and reference voltages.
3.2 Probe orientation and insertion
The orientation dimple on the probe must face upstream.
At least 3 in (7.5 cm) of the probe should be exposed to the airflow to ensure that both the temperature and humidity sensors are fully in the airstream.
Extend the telescopic rod by pulling on the metal tube, never by the cable, to avoid internal wire breakage.
3.3 Display configuration
In the Display Setup menu, up to five parameters can be shown simultaneously (one primary in large font and four secondary). Typical configuration:
Primary: Flow (L/s or CFM) or Velocity (m/s or fpm)
Note: “Pitot Velocity” and “AF Probe Velocity” cannot be active at the same time; only one may be ON or set as PRIMARY.
4. Root-Cause Analysis of “Zero Airflow / Zero Velocity” Symptoms
A frequently reported issue is that the display suddenly shows 0.00 m/s velocity and 0.00 L/s flow, while pressure values remain valid. Based on the manual and field experience, the following causes are most probable.
4.1 Probe recognition failure (most common)
If the main unit cannot read the probe’s EEPROM data, only built-in channels (pressure, temperature, baro) appear, while velocity stays at zero. The troubleshooting table lists:
Symptom: Probe plugged in, but instrument does not recognize it. Cause: Probe was inserted while instrument was ON. Action: Power OFF the unit and turn it ON again.
If the problem persists:
Connector pins may be oxidized or bent;
The probe ID circuit or EEPROM may be defective.
4.2 Burned or open-circuit hot-film element
Inside the 964 probe, the micro-thin film (<100 µm) can be destroyed by high temperature, moisture, or dust contamination. Typical signs:
The probe model appears correctly in the menu;
All velocity readings remain 0.00;
No error message displayed.
Measuring resistance between signal pins with a multimeter helps confirm: an open circuit indicates sensor burnout.
4.3 Incorrect measurement setup
If “Velocity” or “Flow” parameters are disabled in the Display Setup, or if Flow is set as PRIMARY without enabling Velocity as a secondary, the display will not show airflow data.
4.4 Cable or connector damage
Frequent bending or improper storage can break internal wires. Symptoms include intermittent readings when the cable is moved or total loss of signal.
4.5 Faulty probe port on the main unit
When even a known-good probe is not recognized, the main unit’s connector solder joints or signal amplifier may be defective. The manual specifies: “Factory service required on instrument.”
5. Systematic Troubleshooting Procedure
Step
Inspection
Expected Result
Corrective Action
①
Re-plug probe with power off
Unit recognizes probe after restart
If normal → software/recognition issue
②
Check “Probe Info” menu
Displays “964 Probe SN xxxx”
If blank → contact/ID circuit fault
③
Verify Display Setup
Velocity = ON, Flow = ON
If still 0 → hardware failure
④
Swap probe
New probe works
Original probe damaged
⑤
Measure pin resistance
Several hundred–kΩ
Open circuit → hot-film burned
⑥
Restore factory settings / calibration
Reset configuration
If unchanged → return for service
6. Maintenance and Calibration Recommendations
6.1 Routine care
Keep probes clean; avoid oily or dusty airflows.
After use, gently blow dry air across the sensor head.
Store in a dry environment, away from direct sunlight.
Remove batteries during long-term storage to prevent leakage.
6.2 Calibration interval
TSI recommends annual factory calibration to maintain traceable accuracy. Field calibration via the CALIBRATION menu is possible but only for minor adjustments; full calibration must be performed by TSI or an authorized lab.
6.3 Typical calibration specifications
Parameter
Range
Accuracy
Velocity
0 – 50 m/s
±3 % of reading or ±0.015 m/s
Temperature
–10 – 60 °C
±0.3 °C
Relative Humidity
5 – 95 % RH
±3 % RH
Differential Pressure
±3735 Pa
±1 % of reading ± 1 Pa
7. Mechanism of Hot-film Probe Failure
Hot-film velocity sensors are extremely sensitive and delicate. Typical failure mechanisms include:
Burnout of heating element — due to transient over-current or contact bounce;
Condensation — moisture films short or isolate the element;
Cable fatigue — repeated bending leads to conductor breakage.
Failures 1 and 4 are the primary causes of complete loss of velocity signal (“0 m/s”). During repair, check:
Continuity between connector pins and the sensor head;
Visual inspection for dark or cracked sensing film;
Cross-test using another known-good probe.
8. Case Study: Field Repair Example
Background
A laboratory used a TSI 9565-P-NB + 964 probe to measure fume-hood airflow. After about three years of service, the display suddenly showed:
Pressure fluctuating normally, but velocity = 0.00 m/s and flow = 0.00 L/s.
Diagnosis
Probe information visible → communication OK.
Re-plugging did not help.
Sensor head inspection revealed blackened film.
Pin resistance = open circuit.
Resolution
Replaced the 964 probe with a new one.
Instrument operated normally.
Post-calibration deviation < 1.8 %.
Conclusion: The zero-airflow symptom was caused by an open-circuit hot-film element.
9. Using Differential-Pressure Mode as Backup
Even when the velocity probe fails, the 9565-P-NB can still measure airflow via Pitot tube + pressure ports:
Connect Pitot total pressure to “+” port and static pressure to “–”;
Select Flow Setup → Pressure/K-factor and input duct dimensions;
The instrument converts ΔP to velocity using standard equations.
This method provides a temporary substitute for velocity readings until the probe is repaired.
10. Safety and Usage Notes
Avoid electrical hazards: never use near live high-voltage sources.
Do not open the case: user disassembly voids warranty.
Operating limits:
Main unit: 5 – 45 °C
Probe: –10 – 60 °C
Maximum overpressure: 7 psi (48 kPa); exceeding this may rupture the pressure sensor.
11. Conclusion
The TSI 9565-P-NB VelociCalc is a high-precision, versatile instrument integrating differential-pressure, velocity, and humidity measurements in one compact platform. However, in practical field use, the common “airflow = 0” fault is rarely caused by the main unit. Instead, it almost always results from probe recognition failure or hot-film sensor damage.
Adhering to proper operating procedures—power-off insertion, warm-up before zeroing, periodic cleaning, and annual calibration—greatly extends probe life and maintains accuracy.
For maintenance engineers, understanding the signal flow and failure signatures enables quick fault localization and minimizes downtime. For facility managers, implementing a calibration and maintenance log ensures data reliability for HVAC system validation.
From Overheated IGBT Modules to Full System Recovery
1. Introduction
In modern screw air compressors, the variable frequency drive (VFD) is the core component responsible for controlling motor speed and optimizing power consumption. The Chmairss VGS30A compressor, equipped with a 22 kW VEMC inverter, uses variable-speed control to maintain constant discharge pressure while achieving high energy efficiency.
However, after long-term operation, one of the most common issues that field engineers encounter is the “Err14 – Module Overheat” fault on the VEMC inverter. This error not only causes system shutdown but also indicates potential thermal imbalance or hardware degradation inside the inverter.
This article provides a comprehensive technical explanation and a complete repair workflow — from understanding the root cause of Err14, diagnosing the issue step-by-step, to repairing and preventing future failures. It is based on real-world field data from a VGS30A compressor maintenance case.
2. Fault Symptoms and Display Information
(1) On the Main Control Panel (HMI)
The compressor controller repeatedly shows the following message:
STATE: MOTOR INV FAULT
CODE: 00014
Multiple entries appear in the fault history list (024–028), all labeled “MOTOR INV FAULT.”
(2) On the VEMC Inverter Panel
The inverter LED display reads:
Err14
The red alarm indicator is on, and the motor cannot start. Once the contactor closes, the inverter trips immediately.
(3) PLC and System Reaction
The PLC detects the inverter fault signal and sends a stop command to the entire compressor. Frequency display freezes at 0.0 Hz, power output shows 0.0 kW, and total run time stops accumulating.
3. Understanding the “Err14” Code — Module Overheat Fault
The inverter continuously monitors the IGBT module temperature via an NTC thermistor attached to the power module. This analog signal is converted to a voltage and fed to the control CPU through an A/D converter.
Normal temperature range: 25 °C – 75 °C
Warning level: ~85 °C
Trip threshold: ~95 °C
If the module temperature exceeds the limit or the temperature signal becomes abnormal (open circuit, short circuit, or unrealistic value), the inverter will immediately shut down to protect the IGBT module. The control CPU disables PWM output and reports Err14.
4. Common Root Causes of Err14
Based on maintenance experience and field diagnostics, there are five main categories of causes for Err14:
Category
Cause
Description
🌀 Cooling failure
Fan blocked or not running
Dust, oil mist, or worn bearings stop the fan, reducing heat dissipation efficiency.
🌡️ Ambient overheating
Poor cabinet ventilation
When internal cabinet temperature exceeds 45 °C, the module’s junction temperature rises quickly.
🔌 NTC thermistor fault
Broken, oxidized, or loose sensor
The temperature signal becomes unstable or reads as “overheated” even at normal temperature.
⚡ IGBT module damage
Aging or partial short circuit
Localized overheating triggers overtemperature alarm even under light load.
🧭 Control board error
Faulty sampling or amplifier circuit
A/D converter malfunction misreads temperature as extreme value, causing false alarm.
5. Step-by-Step Diagnostic Procedure
Step 1 – Inspect the Cooling Fan and Air Duct
Power on the inverter and check whether the internal cooling fan starts automatically.
If the fan does not spin, measure the voltage at the fan terminals (usually DC 12 V or DC 24 V).
Voltage present but fan not spinning → fan motor failure.
No voltage → main control board output failure.
Clean the air duct, dust filter, and heat-sink fins thoroughly.
Step 2 – Check Cabinet Temperature
Use an infrared thermometer to measure temperature inside the control cabinet.
If it exceeds 45 °C, install additional exhaust fans or ventilation openings.
Avoid placing the cabinet near heat sources (e.g., compressor discharge pipe).
Step 3 – Test the NTC Thermistor
Power off and wait at least 10 minutes for discharge.
Remove the drive or power board.
Measure resistance between NTC terminals (typically around 10 kΩ at 25 °C).
Heat the sensor slightly with a hot-air gun — the resistance should decrease with rising temperature.
If resistance is fixed or open circuit → replace the thermistor.
Step 4 – Check the IGBT Power Module
Use a multimeter diode-test function to check each phase (U, V, W) to positive/negative bus.
Any shorted or low-resistance reading (< 0.3 Ω) indicates IGBT damage.
Verify that the power module is tightly clamped to the heat sink.
Reapply high-quality thermal grease (e.g., Dow Corning 340) if dried or cracked.
Step 5 – Check the Control Board Temperature Circuit
If all above components are normal but Err14 remains:
Inspect connector pins (often CN6 or CN8) for oxidation or loose contact.
Use an oscilloscope to observe temperature signal voltage (should decrease gradually as temperature rises).
Constant 0 V or 5 V output → indicates A/D converter or amplifier failure.
Replace the entire driver/control board if signal circuit is defective.
6. Case Study — Actual Field Repair of a VGS30A Compressor
Equipment details:
Model: Chmairss VGS30A
Inverter: VEMC 22 kW
Total runtime: 7 303 hours
Ambient temperature: ~38 °C
Fault: Err14 appears within seconds after startup; fan not rotating
Inspection and Findings
Component
Result
Action Taken
Cooling fan power
24 V output normal
Fan motor seized → replaced
Air duct
Heavy dust accumulation
Cleaned thoroughly
Thermistor
9.7 kΩ at 25 °C
OK
IGBT module
All phases normal
OK
Thermal grease
Completely dried
Reapplied new grease
Control board
No oxidation or damage
OK
After cleaning and replacing the fan, the inverter started normally. After 30 minutes of continuous operation, module temperature stabilized at 58 °C, confirming successful repair.
7. Electrical and Thermal Theory Behind Err14
(1) Power Loss and Junction Temperature
The IGBT’s heat generation consists of conduction and switching losses: [ P_{loss} = V_{CE} \times I_C + \tfrac{1}{2}V_{CE} I_C f_{sw} (t_{on}+t_{off}) ] If heat cannot be transferred efficiently to the heat sink, junction temperature (Tj) rises sharply, increasing conduction loss — a positive feedback that can lead to thermal runaway and module destruction.
(2) Importance of Thermal Interface
The thermal resistance (Rθjc) between IGBT and heat sink determines how quickly heat is removed. Dried or aged thermal compound increases resistance several times, leading to localized hot spots even when load current is normal.
(3) Protection Logic Inside VEMC Drive
The inverter CPU continuously samples the temperature signal:
Below 0.45 V (≈ 95 °C): trigger Err14 and shut down PWM output.
Above 0.55 V (≈ 85 °C): allow reset condition.
Open circuit: immediate fault lockout, manual reset required.
8. Preventive Maintenance Recommendations
Task
Frequency
Recommended Action
Clean cooling fan and duct
Every 3 months
Use compressed air to remove dust and oil residue.
Replace thermal grease
Every 12 months
Apply fresh silicone-based compound between IGBT and heat sink.
Check ambient temperature
Continuous
Ensure cabinet stays below 40 °C.
Tighten wiring terminals
Every 6 months
Prevent loose or oxidized connections.
Record temperature log
Each service
Document operating temperature trend.
Inspect power module
Upon abnormal fault
Use thermal camera to detect uneven heating.
Regular maintenance can extend inverter lifetime by 30–50 %, reduce downtime, and prevent expensive module failures.
9. Temporary Reset for Diagnostic Verification
If you suspect a false alarm:
Power off and wait at least 10 minutes for cooling.
Power on and press STOP/RESET.
If Err14 reappears immediately → likely sensor or circuit fault.
If it occurs after several minutes of operation → genuine overheating issue.
10. Troubleshooting Flow (Text Version)
Err14 Detected →
↓
Check Cooling Fan Running?
├─ No → Measure fan supply → replace fan if needed
└─ Yes →
↓
Is Ambient Temperature >45°C?
├─ Yes → Improve ventilation
└─ No →
↓
Measure NTC Thermistor Resistance
├─ Abnormal → Replace NTC
└─ Normal →
↓
Inspect IGBT Module & Thermal Grease
├─ Abnormal → Reapply grease / replace module
└─ Normal →
↓
Replace Driver Board (temperature circuit failure)
11. Practical Notes and Safety Reminders
Always discharge DC bus capacitors before touching power terminals (wait >10 minutes).
When replacing thermal grease, ensure no air gaps between module and heat sink.
If replacing the IGBT module, apply torque evenly and use original insulation pads.
Keep cabinet filters clean and avoid placing the compressor near exhaust heat or walls.
Use infrared thermometer to monitor heat sink temperature during first startup after repair.
12. Lessons Learned
This case of the Chmairss VGS30A compressor with VEMC inverter Err14 demonstrates the critical role of thermal management in power electronics. Although the message “Module Overheat” seems simple, it reflects a complex interaction between cooling airflow, thermal interface condition, and signal detection circuits.
Field statistics show:
About 70 % of Err14 faults are resolved by cleaning the cooling path, replacing fans, or re-greasing the module.
The remaining 30 % involve circuit faults or component failures (NTC or driver board).
Understanding these mechanisms allows engineers to diagnose quickly, repair efficiently, and reduce costly downtime.
13. Conclusion
The Err14 (Module Overheat) fault is not merely an alarm — it is the inverter’s self-protection mechanism preventing irreversible IGBT damage. Proper analysis requires both electrical and thermal reasoning. By following the structured diagnostic steps in this guide — inspecting the fan, air duct, thermistor, power module, and control board — maintenance engineers can isolate the root cause systematically.
Regular preventive maintenance, good ventilation, and periodic internal cleaning are the best strategies to ensure long-term reliability of VEMC inverters in air compressor applications.
Polarimeters are widely used analytical instruments in the food, pharmaceutical, and chemical industries. Their operation is based on the optical rotation of plane-polarized light when it passes through optically active substances. Starch, a fundamental carbohydrate in agricultural and food processing, plays a crucial role in quality control, formulation, and trade evaluation. Compared with chemical titration or enzymatic assays, the polarimetric method offers advantages such as simplicity, high precision, and good repeatability — making it a preferred technique in many grain and food laboratories.
The WZZ-3 Automatic Polarimeter is one of the most commonly used models in domestic laboratories. It provides automatic calculation, digital display, and multiple measurement modes, and is frequently employed in starch, sugar, and pharmaceutical analyses. However, in shared laboratory environments with multiple users, problems such as slow measurement response, unstable readings, and inconsistent zero points often occur. These issues reduce measurement efficiency and reliability.
This paper presents a systematic technical discussion on the WZZ-3 polarimeter’s performance in crude starch content measurement, analyzing its optical principles, operational settings, sample preparation, common errors, and optimization strategies, to improve measurement speed and precision for third-party laboratories.
2. Working Principle and Structure of the WZZ-3 Polarimeter
2.1 Optical Measurement Principle
The fundamental principle of polarimetry states that when plane-polarized light passes through an optically active substance, the plane of polarization rotates by an angle α, known as the angle of optical rotation. The relationship among the angle of rotation, specific rotation, concentration, and path length is expressed by:
[ \alpha = [\alpha]_{T}^{\lambda} \cdot l \cdot c ]
Where:
([\alpha]_{T}^{\lambda}) — specific rotation at wavelength λ and temperature T
(l) — optical path length (dm)
(c) — concentration of the solution (g/mL)
The WZZ-3 employs monochromatic light at 589.44 nm (sodium D-line). The light passes sequentially through a polarizer, sample tube, and analyzer. The instrument’s microprocessor system then detects the angle change using a photoelectric detector and automatically calculates and displays the result digitally.
2.2 System Composition
Module
Function
Light Source
Sodium lamp or high-brightness LED for stable monochromatic light
Polarization System
Generates and analyzes plane-polarized light
Sample Compartment
Holds 100 mm or 200 mm sample tubes; sealed against dust and moisture
Photoelectric Detection
Converts light signal changes into electrical data
Control & Display Unit
Microcontroller computes α, [α], concentration, or sugar degree
Keypad and LCD
Allows mode selection, numeric input, and measurement display
The internal control logic performs automatic compensation, temperature correction (if enabled), and digital averaging, ensuring stable readings even under fluctuating light conditions.
3. Principle and Workflow of Crude Starch Determination
3.1 Measurement Principle
Crude starch samples, after proper liquefaction and clarification, display a distinct right-handed optical rotation. The optical rotation angle (α) is directly proportional to the starch concentration. By measuring α and applying a standard curve or calculation formula, the starch content can be determined precisely. The clarity and stability of the solution directly affect both response speed and measurement accuracy.
3.2 Sample Preparation Procedure
Gelatinization and Enzymatic Hydrolysis Mix the sample with distilled water and heat to 85–90 °C until completely gelatinized. Add α-amylase for liquefaction and then glucoamylase for saccharification at 55–60 °C until the solution becomes clear.
Clarification and Filtration Add Carrez I and II reagents to remove proteins and impurities. After standing or centrifugation, filter the supernatant through a 0.45 µm membrane.
Temperature Equilibration and Dilution Cool the filtrate to 20 °C, ensuring the same temperature as the instrument environment. Dilute to the calibration mark.
Measurement
Use distilled water as a blank for zeroing.
Fill the tube completely (preferably 100 mm optical path) and remove all air bubbles.
Record the optical rotation α.
If the rotation angle exceeds the measurable range, shorten the path or dilute the sample.
4. Common Problems and Causes of Slow Response in WZZ-3
During routine use, several factors can cause the WZZ-3 polarimeter to exhibit delayed readings or unstable results.
4.1 Misconfigured Instrument Parameters
When multiple operators use the same instrument, settings are frequently modified unintentionally. Typical parameter issues include:
Setting
Correct Value
Incorrect Setting & Effect
Measurement Mode
Optical Rotation
Changed to “Sugar” or “Concentration” — causes unnecessary calculation delay
Averaging Count (N)
1
Set to 6 or higher — multiple averaging cycles delay output
Time Constant / Filter
Short / Off
Set to “Long” — slow signal processing
Temperature Control
Off / 20 °C
Left “On” — instrument waits for thermal stability
Tube Length (L)
Actual tube length (1 dm or 2 dm)
Mismatch — optical signal weakens, measurement extended
These misconfigurations are the most frequent cause of slow response.
4.2 Low Transmittance of Sample Solution
If the sample is cloudy or contains suspended solids, the transmitted light intensity decreases. The system compensates by extending the integration time to improve the signal-to-noise ratio, resulting in a sluggish display. When transmittance drops below 10%, the detector may fail to lock onto the signal.
4.3 Temperature Gradient or Condensation
A temperature difference between the sample and the optical system can cause condensation or fogging on the sample tube surface, scattering the light path. The displayed value drifts gradually until equilibrium is reached, appearing as “slow convergence.”
4.4 Aging Light Source or Contaminated Optics
Sodium lamps or optical windows degrade over time, lowering light intensity and forcing the system to prolong measurement cycles. Symptoms include delayed zeroing, dim display, or low-intensity readings even with clear samples.
4.5 Communication and Software Averaging
If connected to a PC with data logging enabled (e.g., 5 s sampling intervals or moving average), both display and response speed are limited by software settings. This is often mistaken for hardware delay.
5. Standardized Parameter Settings and Optimization Strategy
5.1 Recommended Standard Configuration
Parameter
Recommended Setting
Note
Measurement Mode
Optical Rotation
Direct α measurement
Tube Length
Match actual tube (1 dm or 2 dm)
Prevent calculation mismatch
Averaging Count (N)
1
Fastest response
Filter / Smoothing
Off
Real-time display
Time Constant
Short or Auto
Minimizes integration time
Temperature Control
Off
For room-temperature samples
Wavelength
589.44 nm
Sodium D-line
Output Mode
Continuous / Real-time
Avoid print delay
Gain
Auto
Optimal signal balance
These baseline parameters restore the instrument’s “instant response” behavior.
5.2 Operational Workflow
Blank Calibration
Fill the tube with distilled water.
Press “Zero.” The display should return to 0.000° within seconds.
If slow, inspect optical or parameter issues.
Sample Measurement
Load the prepared starch solution.
The optical rotation should stabilize within 3–5 seconds.
Larger delays indicate improper sample or configuration.
Data Recording
Take three consecutive readings.
Acceptable repeatability: standard deviation < 0.01°.
Calculate starch concentration via calibration curve.
Post-Measurement Maintenance
Rinse the tube with distilled water.
Perform “factory reset” weekly.
Inspect lamp intensity and optical cleanliness quarterly.
6. Laboratory Management Under Multi-User Conditions
When multiple technicians share the same WZZ-3 polarimeter, management and configuration control are crucial to maintaining consistency.
6.1 Establish a “Standard Mode Lock”
Some models support saving user profiles. Save the optimal configuration as “Standard Mode” for automatic startup recall. If unavailable, post a laminated parameter checklist near the instrument.
6.2 Access Control and Permissions
Lock or password-protect “System Settings.” Only administrators may adjust system parameters, while general users perform only zeroing and measurement.
6.3 Routine Calibration and Verification
Use a standard sucrose solution (26 g/100 mL, α = +13.333° per 100 mm) weekly to verify precision.
If the response exceeds 10 s or deviates beyond tolerance, inspect light intensity and alignment.
6.4 Operation Log and Traceability
Maintain a Polarimeter Usage Log recording:
Operator name
Mode and settings
Sample ID
Response time and remarks
This allows quick identification of anomalies and operator training needs.
Such standardization minimizes human error and prolongs equipment life.
7. Case Study: Diagnosing Slow Measurement Response
A food processing laboratory reported a sudden increase in measurement time — from 3 s to 15–30 s per sample.
Investigation Findings:
Mode = Optical Rotation (correct).
Averaging Count (N) = 6; “Smoothing” = ON.
Sample solution slightly turbid and contained micro-bubbles.
Temperature control enabled but sample not equilibrated.
Corrective Measures:
Reset N to 1 and disable smoothing.
Filter and degas the sample solution.
Turn off temperature control or match temperature to ambient.
Result: Response time returned to 4 s, with excellent repeatability.
Conclusion: Measurement delay often stems from combined human and sample factors. Once parameters and preparation are standardized, the WZZ-3 performs rapidly and reliably.
8. Maintenance and Long-Term Stability
Long-term accuracy requires regular optical and mechanical maintenance.
Maintenance Item
Frequency
Description
Optical Window Cleaning
Monthly
Wipe with lint-free cloth and anhydrous ethanol
Light Source Inspection
Every 1,000 h
Replace aging sodium lamp
Environmental Conditions
Always
Keep in stable 20 ± 2 °C lab with minimal vibration
Power Supply
Always
Use independent voltage stabilizer
Calibration
Semi-annually
Verify with standard sucrose solution
By adhering to this preventive maintenance schedule, the WZZ-3 maintains long-term reliability and reproducibility.
9. Discussion and Recommendations
The WZZ-3 polarimeter’s digital architecture provides high precision but is sensitive to user settings and sample clarity. Slow responses, unstable zeroing, or delayed results are rarely caused by hardware faults — they are almost always traceable to:
Averaging or smoothing functions enabled;
Temperature stabilization waiting loop;
Cloudy or bubble-containing samples;
Aging optical components.
To prevent recurrence:
Always restore “fast response” configuration before measurement.
Use filtered, degassed, and temperature-equilibrated samples.
Regularly calibrate with sucrose standards.
Document all measurements and configuration changes.
Proper user discipline, combined with parameter locking and preventive maintenance, ensures the WZZ-3’s continued performance.
10. Conclusion
The WZZ-3 Automatic Polarimeter is a reliable and efficient instrument for crude starch content analysis when properly configured and maintained. In multi-user laboratories, incorrect parameter settings — especially averaging, smoothing, and temperature control — are the primary causes of slow or unstable readings.
By implementing the following practices:
Standardize instrument settings,
Match optical path length to actual sample tubes,
Maintain sample clarity and temperature equilibrium,
Enforce configuration management and operator training,
laboratories can restore fast, accurate, and reproducible measurement performance.
Furthermore, establishing a calibration and documentation system ensures long-term stability and compliance with analytical quality standards.
The Precisa XM120-HR Moisture Analyzer is designed based on the thermogravimetric principle, specifically tailored for rapid determination of moisture content in powder and liquid samples within laboratory and industrial environments. Its notable technical advantages include:
High-Precision Weighing Technology: Maximum weighing capacity of 124g with a resolution of 0.001g (0.0001g in HR mode), complying with international standards.
Intelligent Drying Control: Supports a three-stage heating program (standard/fast/gentle modes) with a temperature range of 30°C–230°C and customizable drying endpoint conditions.
Data Management Functionality: Built-in storage for 50 methods and 999 measurement records, supporting batch data management and adhering to GLP (Good Laboratory Practice) standards.
User-Friendly Design: Features a 7-inch touchscreen, multilingual interface (including Chinese), and an RS232 port for remote control and data export.
II. Device Installation and Initial Configuration
Unpacking and Assembly
Component List: Main unit, power cord, windshield (1 piece), sample pan holder (2 pieces), sample tweezers (3 pieces), and 80 aluminum sample pans.
Assembly Steps:
Embed the windshield smoothly into the top slot of the main unit.
Install the sample pan holder and rotate to lock it in place.
Insert the sample tweezers, ensuring they are secure.
Environmental Requirements
Location Selection: Place on a level, vibration-free surface with an ambient temperature of 5°C–40°C and humidity of 25%–85% (non-condensing).
Power Connection: Use only the original power cord and ensure reliable grounding. Confirm voltage compatibility for 230V and 115V versions; modifications are prohibited.
Initial Calibration and Leveling
Leveling: Adjust the feet at the bottom to center the level bubble. Recalibrate after each device relocation.
Weight Calibration:
Enter the menu and select “External Calibration” mode. Place a 100g standard weight (accuracy ≤0.001g).
Save the data as prompted and verify the error after calibration.
III. Detailed Operation Procedures
Sample Preparation and Measurement
Sample Handling:
Solid Samples: Grind into a uniform powder and spread evenly on the sample pan (thickness ≤3mm).
Liquid Samples: Use glass fiber pads to prevent splashing.
Starting Measurement:
Press the 《TARE》 button to zero the scale, place the sample, and close the windshield.
Select a preset method or customize parameters, then press 《START》 to initiate.
Drying Program Setup
Multi-Stage Heating:
Stage I (Default): 105°C standard mode for 3 minutes, targeting 75% moisture removal.
Stages II/III: Activate higher temperatures or extend durations for difficult-to-volatilize samples.
Stopping Conditions:
Automatic Stop: When the weight change rate falls below the set value.
Time Stop: Maximum drying time limit.
AdaptStop: Intelligently determines the drying endpoint to avoid overheating.
Data Recording and Export
Batch Processing: Create batches and automatically number samples.
Printing Reports: Output complete reports using the 《PRINT》 button.
RS232 Transmission: Connect to a computer and send the “PRT” command to export raw data.
IV. Advanced Functions and Maintenance
Temperature Calibration
Calibration Tools: Use an optional temperature sensor (Model 350-8585), insert it into the sample chamber, and connect via RS232.
Steps:
Calibrate at 100°C and 160°C, inputting the actual measured values.
Save the data, and the system will automatically correct temperature deviations.
Software Upgrade
Download the update tool from the Precisa website, connect to a PC using a data cable (RJ45-DB9), and follow the prompts to complete the firmware upgrade.
Daily Maintenance
Cleaning: Wipe the sample chamber weekly with a soft cloth, avoiding contact with solvents on electronic components.
Troubleshooting:
Display “OL”: Overload, check sample weight.
Printing garbled text: Verify interface settings.
Heating abnormalities: Replace the fuse.
V. Safety Precautions
Do not analyze flammable or explosive samples, such as ethanol or acetone.
Avoid direct contact with the heating unit (which can reach 230°C) during the drying process; use sample tweezers for operation.
Disconnect the power when not in use for extended periods, store in a dry environment, and retain the original packaging.
Conclusion
The Precisa XM120-HR Moisture Analyzer significantly enhances the efficiency and reliability of moisture detection through its modular design and intelligent algorithms. Users must fully grasp the calibration, program settings, and maintenance points outlined in this manual to maximize device performance. For special samples, refer to the relevant techniques in the manual and optimize parameters through preliminary experiments.
The Reichert AR360 Auto Refractor, developed by Reichert Ophthalmic Instruments (a subsidiary of Leica Microsystems), represents a cutting-edge electronic refraction device that embodies the technological advancements of the early 21st century in automated optometry. This device incorporates innovative image processing technology and an automatic alignment system, revolutionizing the traditional optometry process that previously required manual adjustments of control rods and chin rests.
The core technological advantage of the AR360 lies in its “hands-free” automatic alignment system. When a patient focuses on a fixed target and rests their forehead against the forehead support, the device automatically identifies the eye position and aligns with the corneal vertex. This breakthrough design not only enhances measurement efficiency (with a single measurement taking only a few seconds) but also significantly improves patient comfort, making it particularly suitable for children, the elderly, and patients with special needs.
As a professional-grade ophthalmic diagnostic device, the AR360 offers a comprehensive measurement range:
Sphere: -18.00D to +18.00D (adjustable step sizes of 0.01D/0.12D/0.25D)
Cylinder: 0 to 10.00D
Axis: 0-180 degrees It caters to the full spectrum of refractive error detection, from mild to severe cases.
II. Device Composition and Functional Module Analysis
2.1 Hardware System Architecture
The AR360 features a modular design with the following core components:
Optical Measurement System:
Optical path comprising an infrared light source and imaging sensor
Built-in self-calibration program (automatically executed upon power-on and after each measurement)
Patient observation window with a diameter of 45mm, featuring a built-in green fixation target
Daily: Disinfect the forehead support with 70% alcohol.
Weekly: Clean the observation window with dedicated lens paper.
Monthly: Lubricate mechanical tracks with silicone-based lubricant.
Quarterly: Optical path calibration (requires professional service).
Consumable Replacement:
Printing Paper (Model 12441): Standard roll prints approximately 300 times.
Fuse Specifications:
110V model: T 0.63AL 250V
230V model: T 0.315AL 250V
5.2 Fault Code Handling
Common Alerts and Solutions:
Code
Phenomenon
Solution
E01
Printer jam
Reload paper according to door diagram
E05
Voltage abnormality
Check power adapter connection
E12
Calibration failure
Perform manual calibration procedure
E20
Communication error
Restart device or replace RS232 cable
For unresolved faults, contact the authorized service center. Avoid disassembling the device yourself to prevent voiding the warranty.
VI. Technological Expansion and Clinical Applications
6.1 Comparison with Similar Products
Compared to traditional refraction devices, the AR360 offers significant advantages:
Efficiency Improvement: Reduces single-eye measurement time from 30 seconds to 5 seconds.
Simplified Operation: Reduces manual adjustment steps by 75%.
Data Consistency: Eliminates manual interpretation discrepancies (CV value <2%).
6.2 Clinical Value Proposition
Mass Screening: Rapid detection in schools, communities, etc.
Preoperative Assessment: Provides baseline data for refractive surgeries.
Progress Tracking: Establishes long-term refractive development archives.
Lens Fitting Guidance: Precisely measures vertex distance for frame adaptation.
VII. Development Prospects and Technological Evolution
Although the AR360 already boasts advanced performance, future advancements can be anticipated:
Bluetooth/WiFi wireless data transmission
Integrated corneal topography measurement
AI-assisted refractive diagnosis algorithms
Cloud platform data management
As technology progresses, automated refraction devices will evolve toward being “more intelligent, more integrated, and more convenient,” with the AR360’s design philosophy continuing to influence the development of next-generation products.
This guide provides a comprehensive analysis of the technical principles, operational methods, and clinical value of the Reichert AR360 Auto Refractor. It aims to help users fully leverage the device’s capabilities and deliver more precise vision health services to patients. Regular participation in manufacturer-organized training sessions (at least once a year) is recommended to stay updated on the latest feature enhancements and best practice protocols.
The DOVOL DV950E series permanent magnet synchronous frequency converter is a general-purpose, high-performance current vector frequency converter. It is mainly used to control and adjust the speed and torque of three-phase AC synchronous motors. This guide provides detailed information on the converter’s functional features, operation methods, parameter settings, and troubleshooting, helping users quickly master the skills of using the equipment.
II. Basic Functions and Wiring
Product Main Features
Control Modes: Supports sensorless vector control (SVC), sensor-based vector control (FVC), and V/F control.
Frequency Range: 0 – 500Hz.
Overload Capacity: 150% of the rated current for 60 seconds, 180% of the rated current for 3 seconds.
Speed Regulation Range: 1:50 in SVC mode, 1:1000 in FVC mode.
Built-in PID Regulator: Supports process closed-loop control.
Multiple Communication Protocols Supported: Modbus, ProfiBus-DP, CANlink, CANopen.
Electrical Installation Precautions
Main Circuit Wiring: Correctly distinguish between input terminals (R, S, T) and output terminals (U, V, W).
Braking Resistor: Do not connect the braking resistor directly between the DC bus (+) and (-) terminals.
Motor Cable Length: When the motor cable length exceeds 100m, install an AC output reactor.
Grounding: Ensure reliable grounding with a grounding wire resistance of less than 10Ω.
Power Supply Voltage: Before powering on, ensure that the power supply voltage matches the rated voltage of the frequency converter.
III. Operation Panel Usage
Panel Layout and Indicators
RUN: Running status indicator (lights up when in operation).
LOCAL/REMOT: Control mode indicator (off – panel control; on – terminal control; flashing – communication control).
FWD/REV: Forward/reverse rotation indicator (lights up for reverse rotation).
TUNE/TC: Tuning/torque control/fault indicator.
Five-digit LED Digital Display Area.
Function Keys: PRG (programming), ENTER (confirmation), ▲▼ (increase/decrease), ◄ (shift), etc.
Basic Operation Process
Enter the parameter setting mode by pressing the PRG key.
Select the function group using the ▲▼ keys.
Press ENTER to enter the specific parameter setting.
After modifying the parameter value, press ENTER to save it.
Press the PRG key to return to the previous menu.
IV. Core Function Implementation Methods
Motor Forward/Reverse Rotation Control
Method 1: Panel Control
Set P0-02 = 0 (panel command channel).
Set the running direction via P0-09 (0 – same direction; 1 – opposite direction).
Press the RUN key to start and the STOP key to stop.
Method 2: Terminal Control
Set P0-02 = 1 (terminal command channel).
Assign DI terminal functions: P4-00 = 1 (DI1 for forward rotation), P4-01 = 2 (DI2 for reverse rotation).
Control the on/off state of the DI terminals through external switches to achieve forward/reverse rotation.
Method 3: Communication Control
Set P0-02 = 2 (communication command channel).
Send forward/reverse rotation commands through communication (requires a communication card).
Note: To disable reverse rotation, set P8-13 = 1.
Frequency Regulation Methods
Digital Frequency Setting
Set P0-03 = 0 or 1 (digital setting).
Set the preset frequency via P0-08.
During operation, fine-tune the frequency using the panel ▲▼ keys or UP/DOWN terminals.
Analog Frequency Setting
Set P0-03 = 2 (AI1)/3 (AI2)/4 (AI3).
Configure the curve characteristics of the corresponding AI input (P4-13 – P4-27).
Adjust the frequency using an external potentiometer or PLC analog output.
Multi-speed Control
Set P0-03 = 6 (multi-speed instruction).
Assign DI terminals as multi-speed instructions (P4-00 – P4-09 = 12 – 15).
Set the frequency values for each speed segment in the PC group (PC-00 – PC-15).
PID Frequency Regulation
Set P0-03 = 8 (PID).
Configure the PID parameters in the PA group.
Automatically adjust the frequency based on the feedback signal.
Motor Parameter Tuning
No-load Tuning Steps
Ensure that the motor is mechanically decoupled from the load.
Correctly input the motor nameplate parameters (P1-01 – P1-05).
Set P1-37 = 12 (synchronous motor no-load tuning).
Press the RUN key to start tuning (approximately 2 minutes).
The parameters are automatically saved after tuning is completed.
Loaded Tuning Steps
Set P1-37 = 11 (synchronous motor loaded tuning).
Press the RUN key to start tuning.
The parameters are automatically saved after tuning is completed.
Note: Loaded tuning cannot obtain the back electromotive force coefficient, and the control accuracy is slightly lower than that of no-load tuning.
V. Advanced Function Configuration
Frequency Sweeping Function (Textile Applications)
Set PB-00 = 0 (relative to the center frequency) or 1 (relative to the maximum frequency).
Set PB-01 (frequency sweeping amplitude), PB-02 (jump amplitude).
Set PB-03 (frequency sweeping period), PB-04 (triangular wave rise time).
Control the frequency sweeping pause through the DI terminal (P4-xx = 24).
Fixed-length Control
Set DI5 function as length counting input (P4-04 = 27).
Set PB-07 (pulses per meter).
Set PB-05 (preset length).
Assign DO terminals as length arrival signals (P5-xx = 10).
Counting Function
Set DI terminals as counting input (P4-xx = 25) and reset (P4-xx = 26).
Set PB-08 (preset count value), PB-09 (specified count value).
Assign DO terminals as counting arrival signals (P5-xx = 8 or 9).
Timing Control
Set P8-42 = 1 (timing function enabled).
Set P8-44 (timing operation time) or select AI input via P8-43.
The equipment automatically stops after reaching the preset time.
VI. Fault Diagnosis and Handling
Common Fault Codes and Handling
Fault Code
Fault Type
Possible Causes
Handling Methods
Err02
Acceleration Overcurrent
Short acceleration time/heavy load
Extend the acceleration time P0-17/check the mechanical load
Err03
Deceleration Overcurrent
Short deceleration time
Extend the deceleration time P0-18
Err04
Constant-speed Overcurrent
Load突变 (Load mutation)/motor short circuit
Check the motor insulation/adjust the torque limit P2-10
Err09
Undervoltage
Low input voltage/power outage
Check the power supply voltage/set P9-59 for instantaneous power failure without stop
Err11
Motor Overload
Heavy load/undersized motor
Reduce the load/check the rated current setting P1-03
Err14
Module Overheating
High ambient temperature/poor heat dissipation
Improve the heat dissipation conditions/reduce the carrier frequency P0-15
Err20
Encoder Fault
Signal interference/wiring error
Check the encoder wiring/set P2-32 = 0 to disable Z correction
Fault Reset Methods
Panel Reset: Press the STOP/RES key in the fault state.
Terminal Reset: Set the DI terminal function to 9 (fault reset).
Communication Reset: Send a reset command through communication.
Fault Record Inquiry
Recent Fault: Check P9-16 – P9-22.
Second Fault: Check P9-27 – P9-34.
First Fault: Check P9-37 – P9-44.
VII. Maintenance and Upkeep
Daily Inspection
Check if the cooling fan is operating normally.
Check for loose wiring terminals.
Check if the enclosure temperature is abnormal.
Regularly remove dust from the radiator.
Regular Maintenance
Check the appearance of electrolytic capacitors every six months.
Check the insulation resistance annually (measure after powering off).
Replace the cooling fan every 2 years (depending on the operating environment).
Parameter Backup
Set PP-01 = 4 (backup user parameters).
To restore, set PP-01 = 501.
Restore to factory settings: PP-01 = 1.
VIII. Safety Precautions
Do not open the cover when powered on. After powering off, wait for 10 minutes before performing wiring operations.
Do not connect the braking resistor directly to the DC bus.
Perform an insulation check on the motor before the first use (≥5MΩ).
Derate the equipment when the altitude exceeds 1000m (derate by 1% for every 100m).
Derate the equipment when the ambient temperature exceeds 40℃ (derate by 1.5% for every 1℃).
Do not install capacitors or surge suppressors on the output side of the frequency converter.
This guide provides a detailed introduction to the various function implementation methods of the DV950E frequency converter. When using it in practice, please select the appropriate configuration method according to the specific application scenario. For complex application scenarios, it is recommended to contact the manufacturer’s technical support for more professional guidance.
