Honeywell 51305890-175 Thermocouple Multiplexer Board

Product Overview

The Honeywell 51305890-175 handles thermocouple signal multiplexing for temperature measurement applications. This circuit board accepts multiple thermocouple inputs and routes them to the analog input module. It consolidates temperature signals from various plant locations efficiently. The unit integrates into Honeywell Series C and TDC 3000 cabinet systems.

Technical Specifications

Parameter	Specification
Model Number	51305890-175
Product Type	Multiplexer Thermocouple Circuit Board
Number of Inputs	16 thermocouple channels
Thermocouple Types	J, K, T, E, R, S, B, N
Input Connector	Screw-clamp terminal blocks
Cold Junction Compensation	Built-in with thermistor sensor
Compensation Accuracy	±0.5°C typical
Channel Isolation	None (common ground)
Scan Rate	20 channels per second
Power Supply	5 VDC from backplane
Power Dissipation	2.5 W typical
Operating Temperature	0°C to 60°C
Storage Temperature	–40°C to 85°C

Physical Dimensions and Construction

This circuit board measures 215 mm in width, 165 mm in depth, and 45 mm in height. The unit weighs approximately 0.50 kg. It mounts vertically on DIN rails or directly onto cabinet backplates. The board includes clearly labeled terminal positions for each channel. A built-in cold junction temperature sensor sits near the terminal blocks.

Electrical Interface and Field Wiring

Screw-clamp terminal blocks provide the primary interface for all thermocouple wiring connections. Each channel accepts solid or stranded thermocouple extension wire. The board uses a common ground reference for all input channels. A 50-pin ribbon cable connector links the board to the analog input module. The multiplexer scans each channel sequentially and forwards the signals. This design reduces the number of analog input channels required.

Signal Processing and Cold Junction Compensation

The 51305890-175 incorporates automatic cold junction compensation for accurate temperature readings. A precision thermistor monitors the terminal block temperature continuously. The board compensates each thermocouple reading using this reference temperature. It scans all 16 channels at a rate of 20 readings per second. The multiplexer output connects to a single analog input channel. Consequently, this approach maximizes the use of available I/O capacity.

Installation and System Integration

You can install this board in any Honeywell Series C or TDC 3000 cabinet. The mounting holes align with standard DIN rail profiles for quick installation. Always use the correct thermocouple extension wire for your sensor type. Connect the positive and negative leads according to the terminal markings. Avoid running thermocouple wiring parallel to power cables. This precaution prevents electrical noise interference with temperature signals.

Environmental Compliance and Durability

This board meets RoHS requirements for restricted substance content. It also carries UL 508 recognition for industrial control equipment. The conformal coating protects the PCB against moisture and airborne contaminants. This coating ensures reliable operation in typical plant environments.