Watlow Series 942 Controller

Watlow Series 942 Controller

Core features and specifications of the product

core functionality

Control mode: Supports PID or ON/OFF control, can be manually selected; Dual output design, output 1 can be set as heating or cooling, and output 2 can be set as heating, cooling, or off.

Input type: compatible with J, K, T, N, R, S, B, C, Pt2 thermocouples, RTD (2-wire or 3-wire) and 0-5VDC, 4-20mA process inputs.

Programming ability: Supports 24 step program curves, including four step types: set point (StPt), constant temperature (SoAh), jump cycle (JL), and end, and can achieve multi-stage temperature control.

Auxiliary functions: optional dual auxiliary output (alarm or time triggered event), set point/process value retransmission output, supports RS-422A/RS-423A/EIA-485 communication interface.

Data storage: Non volatile memory automatically saves all parameters, and data is not lost after power failure; Lithium battery backup operation parameters, with a service life of about 10 years.

Key specifications

Temperature range: thermocouple (-328 ° F~4200 ° F/-200 ° C~2315 ° C), RTD (-328 ° F~1112 ° F/-200 ° C~600 ° C), process input (-500~3500 units).

Accuracy: ± 0.1% ± 1 LSD of full scale (ambient temperature 77 ° F ± 5 ° F, rated voltage ± 10%).

Output specifications:

Solid state relay output: 0.5A@24-264VAC Optical isolation and zero crossing switching.

Mechanical relay output: 6A@120 /240VAC or 28VDC.

Process output: 0-5VDC/0-10VDC (minimum load 10K Ω), 4-20mA/0-20mA (maximum load 600 Ω).

Working environment: Temperature range of 32 ° F~149 ° F (0 ° C~65 ° C), humidity range of 0~90% (no condensation).

Installation and wiring process

Installation preparation

Panel Hole: Process panel holes according to size requirements (nominal 3.625 × 3.625 inches/92.08 × 92.08mm, thickness 0.06~0.25 inches/1.5~6.35mm).

Equipment fixation: Insert the controller housing into the opening, fix it from the back of the panel with the matching bracket, then insert the control chassis into the housing and lock it by rotating the front plate screw 90 ° clockwise (note that the screw should only be rotated 90 ° to avoid excessive force damage).

Wiring operation

Power wiring

Supports 120VAC or 240VAC power supply (50/60Hz universal, no adjustment required), requires connection to L1 and L2 power terminals and grounding terminals, and wiring must comply with the National Electrical Code (NEC) to avoid the risk of electric shock.

The power supply end needs to be connected in series with a fuse. When powered by 120VAC, the L1 end needs to be connected in series with a fuse. When powered by 240VAC, both the L1 and L2 ends need to be connected in series with a fuse.

Sensor wiring

Thermocouple: Use extension cords made of the same material as the thermocouple to avoid errors; If connecting non isolated external devices, an isolated thermocouple should be selected, with positive and negative terminals corresponding to terminals 7 (+) and 9 (-).

RTD: 2-wire RTD needs to short-circuit terminals 5 and 6, and 3-wire RTD needs to ensure that the resistance of the three extension wires is consistent (with the same wire diameter and material) to compensate for lead resistance errors (every 1 Ω lead resistance of 2-wire RTD will cause an error of about+2 ° C).

Process input: 0-5VDC input is connected to terminals 1 (+) and 3 (-), with an input impedance of 100K Ω; 4-20mA input requires short circuiting terminals 2 and 3, followed by connecting the positive and negative poles of the signal, with an input impedance of 249 Ω.

Output wiring

Output 1/2: Select the wiring method according to the model (solid-state relay, mechanical relay, DC switch, process output, etc.), refer to the wiring diagram of the corresponding model in the manual for details, and ensure that the load impedance matches (such as process output 4-20mA maximum load 600 Ω).

Auxiliary output: 6 auxiliary options are available (single relay, dual relay, relay+retransmission, etc.), wired according to the corresponding terminals (24-27) of the model, and the alarm/event output is a mechanical relay（ 6A@28VDC /120VAC）。

Wiring precautions

Separation of strong and weak electricity: The sensor signal line (low power) is wired separately from the power line and output line (high power), with a minimum spacing of 12 inches (305mm) to avoid cross interference; When crossing, use a 90 ° crossing.

Shielding and grounding: Shielded cables are used for low-level signal lines, and the shielding layer is only grounded at the controller end; The system is grounded at a single point to avoid grounding loops, and all grounding terminals are connected to a unified grounding body.

Parameter Configuration Guide

Enter the configuration menu

Press the UP and DOWN keys simultaneously for 3 seconds to enter the Setup menu (displaying LOC parameters); Continue holding down the UP and DOWN keys under the LOC parameter to enter the calibration menu.

During the configuration process, press the MODE key to switch parameters, use the UP/DOWN key to adjust values, and if there is no operation for 5 seconds, it will automatically save and return to the previous level, or press the MODE key to manually save and switch.