Resistance Input mode (Passive Input)
Passive Inputs are all those devices that vary in resistance, including switch contacts.
These all require a current supplied by the CBXi-8R8(-H) terminal so that this resistance can be measured.
The passive sensor types supported by the CBXi-8R8(-H) are:
• Pre-programmed Passive Temperature Sensors.
• Potentiometer (normally used as a 0 to 10 KΩ or a 1 KΩ to 11 KΩ variable resistor to give a 0 to 100 %
output).
• Volt-Free Digital Input (the controller strategy measures the contact resistance and gives a 0 or 1
output).
• Straightforward Resistance measurement. This can be used with the Make Linear block to give a
temperature output for temperature sensors that are not factory pre-programmed into the CBXi-
8R8(-H).
In CXproᴴᴰ simply select ‘Resistance’ sensor type in the Point Module and select Pulsed in the Advanced
parameters (the Pulsed option increases accuracy by eliminating any self-heating in the passive
temperature sensor, while the Continuous option can trade absolute accuracy for speed).
In Passive Input Mode the Uniputs™ and Universal Inputs configure like this:
Note: The reference voltage can be pulsed or continuous, using the solid state switch.
A pulsed reference gives optimum accuracy by eliminating self-heating in the sensor, and this is the
default setting.
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