Watlow PM LEGACY ™ Limit controller

Watlow PM LEGACY ™ Limit controller

Product Core Information

Product positioning: Industrial grade PID controller, suitable for basic temperature control and limit monitoring scenarios, supporting composite functions such as PID control, limit detection, and multi class alarms.

Model specifications: available in two panel sizes: 1/32 DIN (PM3) and 1/16 DIN (PM6), supporting AC/DC dual power supply mode and compatible with multiple input/output configurations.

Core advantages: simple and easy to operate menu, PID self-tuning function, multi bus communication support, FM certified over/under temperature protection, three-year warranty, and features such as touch safe packaging, waterproof and dustproof (NEMA 4X/IP66/IP67).

Product Features and Technical Parameters

（1） Input function

Analog input

Type and Range: Supports thermocouples (such as J, K, T, E, etc., with different measurement ranges for different types, such as J type -346 to 2192 ° F, i.e. -210 to 1200 ° C), RTDs (calibrated at 100 Ω, 1k Ω, 0 ° C, in accordance with DIN curves, 2-3 wire system, 20 Ω total lead resistance, typical excitation current 0.09mA, lead resistance per ohm may cause 0.03 ° C reading deviation), thermistors (5k Ω, 10k Ω, 20k Ω, 40k Ω), process signals (voltage 0-10VDC, input impedance 20k Ω; current 0-20mA, input impedance 100 Ω); Millivolt 0-50mVdc, input impedance 20k Ω), 1k Ω potentiometer, and all analog inputs can be scaled to meet different measurement requirements.

Configuration requirements: Sensor type (sEn), linearization (Lin, for thermocouples), number of leads (rt.L, for RTDs), unit, scaling high and low values (s.Lo, s.hi), range high and low values (r.Lo, r.hi) and other parameters need to be configured in the "Setup Page - Analog Input Menu" to ensure compatibility with the connected input device. For example, thermocouples should pay attention to polarity (negative pole is usually red, connected to S1 terminal), and the extension wire should be made of the same material as the thermocouple to reduce errors; The S1 lead (usually white) of a 3-wire RTD needs to be connected to R1 and/or R2 terminals, and the resistance of the three leads must be consistent to ensure accuracy.

Performance indicators: thermocouple input impedance>20M Ω, maximum source resistance 2k Ω, with 3 µ A open circuit sensor detection function; The input accuracy of RTD is affected by lead resistance and needs to be compensated through calibration; The scaling range of process input can be set according to actual needs, such as 4-20mA corresponding to 0-100% humidity, etc.

Digital input

Hardware configuration: The model with Digital Input/Output (DIO) hardware includes two sets of terminals (5 and 6), each set can be configured as an input or output, and needs to be set through the "Direction" parameter in the "Setup Page Digital Input/Output Menu" (input can choose voltage input or dry contact input).

Input characteristics: When voltage is input, the maximum input voltage is 36Vdc, the activation voltage is>3Vdc (0.25mA), and the non activation voltage is<2VDC; When using dry contact input, the activation resistance is less than 100 Ω, the non activation resistance is greater than 500 Ω, and the maximum short-circuit current is 13mA. The update rate is 10Hz, which can be used to detect equipment start stop status, external trigger signals, etc.

Special Input: The Reset button on the front of the controller can be configured as a digital input through the "Digital Input Function" parameter in the "Setup Page Reset Key Menu" to achieve function switching, such as limit reset, alarm mute, etc.

（2） Output function

Output type and characteristics

Mechanical relay: Form C type (output 1, 3), rated load 5A@240Vac Or 30Vdc (resistive), minimum load 20mA@24V ， 125VA pilot duty at 120/240Vac, 25VA pilot duty at 24Vac, with a lifespan of 100000 cycles (rated load), supporting AC/DC loads, no power output, requiring external power supply; Form A type (outputs 2 and 4) has parameters similar to Form C type, with only normally open contacts. Output 2 is default bound to the limit function and serves as the main output for limit protection.

Solid state relay (SSR): Form A type (output 3, 4), rated load 0.5A@20-264Vac (Resistive), 20VA pilot duty at 120/240VAC, optocoupler isolation, contactless suppression, maximum off state leakage current of 105 µ A, minimum holding current of 10mA, only supports AC load, no power output.

Switching DC/collector open circuit output: Supports outputs 1, 3, and 4, with a maximum open circuit voltage of 22-25Vdc, a maximum current of 30mA for a single output, and a maximum total current of 40mA for paired outputs (1&2, 3&4). Typical driver 4.5Vdc@30mA Short circuit current limit<50mA (NPN transistor current), can drive external solid-state relays, supports multiple sets of DIN-A-MITE relays in parallel/series (such as 1 pole up to 4 sets in parallel/series, 2 poles up to 2 sets in parallel/series, 3 poles up to 2 sets in series).

Universal process output: Only supports 3 outputs, can be configured as voltage (0-10VDC, minimum load 1k Ω) or current (0-20mA, maximum load 800 Ω) output, with scaling function (s.Lo, s.hi, r.Lo, r.hi), can be used to retransmit process values or set values, output accuracy ± 15mV (voltage), ± 30 µ A (current), temperature stability 100ppm/° C, need to configure parameters such as type (o.ty), function (fn), and retransmission source (r.Sr) in the "Setup Page Output Menu".