Analog inputs on a MicroSmart controller are all reading a negative value.

Issue

Analog inputs on a MicroSmart controller are all reading a negative value.

Product Line

TAC I/A Series

Environment

MicroSmart controllers (all versions)

Cause

Hardware issue or sensor failure

Resolution

If the connected sensor is a RTD, a negative reading reflects an electrical short somewhere between the controller and the sensor.  Note that a high positive reading reflects an electrical open circuit.

If the connected sensor is a 4-20 mA device, it typically reads a high positive value which reflects an electrical open circuit.