Greystone manufactures Signal Isolators to eliminate ground loop wiring issues. A ground loop circuit happens with different earth potentials allowing current flow between two grounds. Ground loops cause problems with the receiving device being unable to differentiate between signals causing an inaccurate reading.

The GT-AI-420 is powered by the output current loop so an additional power supply is not required. The GT-AI-420 accepts a voltage or current input signal converting to an isolated 4-20mA (current sinking) output. This type of 2-wire loop isolator can be placed anywhere between the field sensory transmitter and the PLC/BAS controller.

Greystone also offers a GT-AI Signal Isolator with more features such as: Sink or Source ability, power with voltage & current, preset & adjustable signal limiting ranges, and normal or reverse operation with 1% accuracy. The device must use 24Vac to provide a 3-way isolation of power, input and output signals preventing a ground loop condition. This versatile control solution can be used for isolating variable speed drives or data logger signals to an energy management system.

Sink Vs Source 4-20mA signal

As seen in the diagram to the right, Sink is acting as a resistive load (meaning it needs a supply voltage from something else to act as a load); whereas Source means it’s supplying the voltage for the current.