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 FLX terminal so that this resistance can be measured.
The passive sensor types supported by the FBXi 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 FBXi.
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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