Watlow PM3 LEGACY ™ PID controller



Watlow PM3 LEGACY ™  PID controller

Product Core Information

Watlow PM3 LEGACY ™  PID is a 1/32 DIN panel mounted high-precision temperature controller that adopts universal input and multi output configurations, supports PID/switch control modes, and is suitable for industrial temperature regulation, process monitoring, and other scenarios. The product complies with the ISO 9001 standard, has an IP65 (NEMA 4X) protection level, supports multi country certifications such as CE, UL, CSA, etc., provides a 3-year warranty, and is equipped with dual four digit red and green LED displays. It is easy to operate and compatible with multiple communication protocols.

Core specification highlights:

Input type: compatible with J/K/T/N/E/R/S/B thermocouples, 2/3 wire RTD (100 Ω/1k Ω), thermistor, potentiometer, 0-10V voltage/0-20mA current and other process signals.

Output configuration: Supports switch DC, mechanical relay (5A), solid-state relay (0.5A), 4-20mA process output, and can be configured with heating, cooling, alarm, retransmission and other functions.

Control accuracy: Calibration accuracy ± 0.1% range (± 1 ° C @ 25 ° C environment), sampling rate 10Hz, display update rate 1Hz, temperature stability ± 0.1 ° C/° C environmental changes.

Key functions and features

（1） Control and tuning functions

PID control: supports P, PI, PD, PID, and switch control, with parameters including proportional band, integral (reset), and derivative (rate), which can be optimized through self-tuning or manual calibration; The switching difference of the switch control can be customized.

Self tuning and adaptive tuning:

Autotune: Based on 90% of the set value as a reference, the system characteristics are "learned" through 5 temperature cross tests. If not completed within 60 minutes, it will automatically exit. It supports three response modes: under damping, critical damping, and over damping.

TRU-TUNE+ ®  Adaptive tuning: Real time monitoring of process values, automatic adjustment of PID parameters to adapt to load changes, support for bandwidth and gain customization, suitable for dynamic process control.

Ramp/Soak: Supports 4 configuration files, with up to 40 steps per file. The heating rate (℃/minute/hour) and constant temperature time can be set, and the step types include heating, constant temperature, waiting for events/processes, jump cycles, etc., to meet the requirements of complex temperature control processes.

（2） Alarm and safety functions

Alarm type: Supports process alarm (absolute temperature threshold) and deviation alarm (relative to set value), 4 independent alarm channels, configurable high/low threshold and hysteresis (to avoid frequent alarms).

Alarm auxiliary function: supports locking/non locking mode (locking needs to be manually cleared), alarm mute, alarm blocking when starting/setting value changes. The alarm output logic can be set to "energize when alarm" or "de energize when alarm".

Fault protection: equipped with sensor open/short circuit detection, open-loop detection (monitoring process value deviation when output is 100%), input error handling (configurable to switch to manual mode or turn off output without disturbance).

（3） Auxiliary functions

Data storage: non-volatile memory, parameters are not lost after power failure, supports saving and restoring 2 sets of user configurations, and can quickly reuse parameter settings.

Display customization: Users can customize homepage parameters (up to 20), support display switching, automatic scrolling, and adapt to different operational scenarios.

Communication compatibility: Supports EIA-485, Modbus RTU, Bluetooth (optional), can be remotely configured and monitored through PC software (EZ-ZONE Configurator), supports networking with 247 Modbus nodes.

Installation and wiring

（1） Installation requirements

Panel incision size: 53.3mm (width) × 30.9mm (height), panel thickness: 1.53-9.52mm, fixed with snap on installation ring, IP65 protection needs to ensure that the sealing gasket is not twisted and installed in place.

Environmental restrictions: Operating temperature 0-65 ° C, storage temperature -40-85 ° C, relative humidity 0-90% (no condensation), suitable for Class I, Div.2 hazardous areas (some models).

（2） Wiring specifications

Power wiring: Supports 85-264V AC, 12-40V DC, or 20-28V AC, with built-in slow melting fuses (high voltage type 1A, low voltage type 2A), and must comply with NEC electrical standards.

Input wiring:

Thermocouple: The extension wire should be made of the same material as the thermocouple, and the positive and negative poles should be distinguished (red is usually the negative pole) to avoid polarity reversal.

RTD: The 3-wire system can compensate for lead resistance, and the three leads must have the same specifications (same wire diameter, same length), with a total lead resistance of ≤ 20 Ω.

Process signal: 0-20mA current input impedance of 100 Ω, 0-10V voltage input impedance of 20k Ω, ensuring that the signal source and controller are grounded together.

Output wiring: Inductive loads (such as relay coils) need to be paired with RC suppressors (Watlow part number 0804-0147-0000); It is recommended to extend the cycle of mechanical relays to reduce contact wear, while solid-state relays can shorten the cycle and improve control accuracy.

Operation and Configuration

（1） Menu Structure and Navigation

Menu Type Entry Method Core Functions

Home: Power on default or press and hold the infinite key for 2 seconds to view/modify commonly used parameters such as settings, control modes, and self-tuning startup

Press and hold the up and down arrow keys for 3 seconds in the Operations menu to monitor process values, adjust PID parameters, alarm thresholds, and view operating status

Press and hold the up and down arrow keys for 6 seconds in the Setup menu to configure basic parameters such as input type, output function, communication parameters, alarm logic, etc

Program menu (Profiling): Long press the forward button for 3 seconds to edit the slope/constant temperature program, step parameters, and number of cycles

Factory Menu: Long press the forward button and infinite button for 6 seconds to calibrate, password lock, restore factory settings, and customize the homepage

（2） Core configuration steps

Input type configuration: Select the sensor type (such as thermocouple J type, 100 Ω RTD) from the "Analog Input" menu in the settings, and match the wiring method (such as RTD 2/3 wire system).

PID self-tuning start: Set "Autotune" to "YES" in the operation menu, and the controller will automatically enter the tuning mode. The homepage will display the prompt "tUN1", and the optimal PID parameters will be automatically saved after completion.

Slope/constant temperature program configuration: Create steps in the program menu (such as heating rate of 5 ℃/min, constant temperature of 30 minutes), support jump loop (up to 4 nested layers), and can be started/stopped through digital input or panel operation.

Alarm configuration: Select the alarm type (process/deviation), threshold, and hysteresis in the settings menu, configure the lockout/mute function, and display normal parameters and alarm information alternately on the homepage when the alarm is triggered (such as "AL. h1" indicating high alarm 1).

（3） Keys and Display

Key functions: forward key (switch parameters), infinite key (return to home page/clear alarm), up and down arrow keys (adjust values), support parameter self input (automatic confirmation after 3 seconds without operation).

Display screen: The upper screen displays the process value (PV), the lower screen displays the set value (SP)/parameter name, flashes the alarm code when an alarm is triggered, and displays "----" when a sensor fails.

Troubleshooting and Maintenance

（1） Common fault handling

Possible causes and steps for troubleshooting

No display power not connected, fuse blown, wiring error. Check the power voltage, replace the fuse, and verify the power wiring (terminals 98/99)

Sensor malfunction (Er. i1): Sensor open/short circuit, reverse polarity, type mismatch. Check the wiring and integrity of the sensor, and confirm that the sensor type in the settings menu is consistent with the actual one

No output action output function configuration error, load fault, control mode is "Off". Check the output function in the settings menu (such as heating/cooling), check the load and fuse, and switch the control mode to "Auto"

Temperature overshoot/large fluctuation. Improper PID parameters, incomplete self-tuning. Restart self-tuning, or manually adjust the proportional band (increase to reduce fluctuations) and derivative (increase to suppress overshoot)

Communication failure: baud rate/address mismatch, wiring error. Check the communication parameters (Modbus address, baud rate) in the settings menu and verify the EIA-485 wiring (T+/T -/common terminal)

（2） Maintenance points

Regular calibration: It is recommended to calibrate the input/output accuracy once a year using precision millivolt sources, resistance boxes, and other equipment. Offset and slope adjustments can be made through the "Calibration" menu in the factory.

Terminal maintenance: Check the tightness of the wiring (torque 0.56 Nm) to avoid poor contact caused by vibration; The lifespan of mechanical relays is about 100000 cycles, and it is recommended to use solid-state relays for high-frequency switching scenarios.

Software update: The EZ-ZONE Configurator software can be used to upgrade firmware, backup/restore configuration parameters, and avoid parameter loss caused by misoperation.