IO171 Terminal Board
IO171 Terminal Board — Terminal board manual for the
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.
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.
The numbers on the connectors indicate the corresponding channels. The labels on
top of the connectors indicate the function (Ex+, Ex-, Ain+, Ain-).
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.
The wiring scheme for RTDs is as follows:
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.
Set the switches to OFF (2-wire) when there are two wires running to
the RTD. This option provides the best accuracy.
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 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 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.
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) |
These dimensions do not include the DIN rail clips.