5.2.14.1 Sensor Break Impedance

In some cases the sensor may not immediately break but corrosion may lead to a high impedance condition.

 

1. For thermocouples a break is indicated if the impedance is greater than about 20KΩ.

2. For a PRT input, sensor break is indicated if any one of the three wires is broken or if the source resistance exceeds about 420Ω or falls below about 15Ω.

3. For mA and volts input sensor break will not be detected due to the load resistor connected across the input terminals.