Live zero is a key advantage of 4-20mA instrumentation signals.

Using Ohms Law (E=IxR), with I = 4mA and R = 250 ohms, we see that the minimum measurement would be 1Vdc.

If the range of the voltage trend recorder is 0-5V, any measured value below 1V indicates an electrical problem. A supply fuse failure or tripped breaker will be immediately reported.

Where is this important? Depending on the software capabilities, this can be processed as an alarm or recorded in the data for analysis later.

Loop wiring consists of a 2 wire connection. With the installation of a standard 2 wire cable, installation can be very simple. With location of the transmitter power supply next to the measurement system; the installation of a jumper between supply – and measurement system -; all that is required is a connection from the transmitter + to the power supply +, and a connection from the transmitter – to measurement channel, to complete a loop transmitter signal connection.

This is key as other methods of signal conditioning may require, a 3 wire or 4 wire connection between the conditioner and measurement system, depending on the type of conditioner.

Why is this important? In addition to the complexity being decreased, the cost of the cable decreases as well.

The ROI-XMA is an improved way to read sensors. Multiple sensor types. Multiple signal ranges. High linearity. High precision. Fast response. Long transmission distances. True analog signal conditioning, not microprocessor based A-D conversion.