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Documentation
CONTENTS
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IO171 Terminal Board

IO171 Terminal Board — Terminal board manual for the I/O module

Overview

The Speedgoat IO171 Terminal Board is a dedicated terminal board for RTDs, strain gauges and thermocouples (including cold junction compensation). It allows individual wiring schemes to be implemented for each channel.

Switches

Each channel has two switches which allow the excitation voltage to be directly connected to the sensor terminal (Ain+ & Ain-). Consequently, jumper wires are not needed for two-wire RTD measurements.

Cold Junction Compensation

The cold junction compensation for thermocouples is achieved by an isothermal block which thermally connects all 32 sensor terminals (Ain+ and Ain-). The IO171 automatically measures the temperature of the aluminum block using an SE95 thermal sensor. The casing further helps to balance the temperature.

Labelling

The numbers on the connectors indicate the corresponding channels. The labels on top of the connectors indicate the function (Ex+, Ex-, Ain+, Ain-).

Wiring schemes

This section describes three connection configurations for three corresponding types of sensor.

The switches provide a choice between two configurations. In both cases the switch between EX+ and Ain+ must be in the same position as the one between Ex- and Ain- for the same channel.

The switch position (ON/OFF) is indicated on the switch itself.

RTDs

The wiring scheme for RTDs is as follows:

  1. Set the switches to ON (4-wire) when there are four wires running to the RTD. The connection of the excitation current to the RTD occurs directly on board. This option provides the least accuracy.

  2. Set the switches to OFF (2-wire) when there are two wires running to the RTD. This option provides the best accuracy.

Thermocouples

Thermocouples are wired as follow:

Thermocouples do not require any external excitation. When connecting thermocouples, the switches must be set to OFF (2-wire).

The "Cold junction compensation" field in the IO171 analog input Simulink block must be set to "External Sensor".

Strain gauges

Strain gauges are usually measured with a quarter-bridge or a half-bridge configuration. This requires four-wire wiring, meaning that the switches must be set to OFF.

Cable installation

To achieve a thermally optimal measurement environment, cables are run outside the IO171 Terminal Board through a slit using insulating foam. This solution reduces thermal exchanges between the inside and outside of the IO171 Terminal Board.

Remove the transparent lid and front wall as shown below.

After connecting the sensor cables, re-insert the front wall completely and slide the lid back on.

To connect the IO171 Terminal Board to a Speedgoat real-time target machine, use the 68-way MDR-SCSI cable provided.

DIN rail mount

The IO171 terminal board is supplied with two DIN rail mount clips.

Dimensions

The mechanical dimensions are as follows (with the IO171 Terminal Board placed vertically and the SCSI3 connector on top):

Height (mm) Width (mm) Depth (mm)
129 12548

These dimensions do not include the DIN rail clips.