When the conductive path between the differential voltages is broken, a current cannot form. So what can be done? Use a signal isolator to “break” the galvanic path between the two grounds. From a practical standpoint, you cannot reach into the earth and regulate the voltage at these permanent ground points. The process which, in turn, is in physical contact with the ground. It’s also possible that the ground exists because the instrument is in physical contact with The ground may be required for the safe operation of an electronic device. Why? Because you cannot always control the number of grounds, and it is often impossible to just “lift” a ground. The challenge is, the first and second conditions are not plausible candidates for elimination. To remove the ground loop, any one of these three conditions must be eliminated. There is a galvanic path between the grounds.The grounds are at different potentials.This current path, known as a ground loop, is a very common source of signal inaccuracies.Ī ground loop forms when three conditions are present: When this happens, an additional and unpredictable amount of current is introduced into the loop, which distorts the true measurement. But when the voltages (V) at the two ground points are different, a circulating, closed current (I) path is formed by the copper wires used for the 4-20mA signal and the ground. The loop in question may be as simple as a differential pressure (DP) transmitter sending a 4-20mA measurement to a receiver, such as a recorder. However, it was soon discovered that when 4-20mA (or other DC) signal wires have paths to ground at both ends of the loop, problems are likely to occur. Electronic transmitters were quickly replacing their pneumatic predecessors because of cost, installation, maintenance and performance advantages.
The need for signal isolation began to flourish in the 1960s and continues today.
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