Terminal Configurations (Analog Input Ground Reference Settings) for Isolated Devices

You can use differential, referenced single-ended (RSE), or nonreferenced single-ended (NRSE) terminal configurations (or analog input ground reference settings) for isolated devices.

The following figure shows a differential measurement system. For illustrations of other terminal configurations, refer to your device documentation.

RSE and NRSE measurement systems are the same for isolated devices in that the measurement is made with respect to a floating or isolated ground, AI GND. AI GND is the floating reference for all RSE and NRSE channels. AI GND is isolated from earth ground through an isolation barrier on the device.

It is important to keep within the specifications of your device to avoid hazardous conditions. It is considered improper use of the device to surpass the specifications, and the device is no longer considered to be in safe use. Isolated devices specify a continuous working isolation voltage that specifies the maximum voltage difference allowed between any of the input signals to the chassis/earth ground. For example, a product rated for 60 VDC of continuous working isolation that has a voltage difference of +51 VDC between AIGND and the chassis/earth ground cannot have a signal greater than +9 VDC when referenced to a AIGND or 60 VDC when reference to chassis/earth ground at its input terminals.