Current Loops can be 2-wirel, 4-wire, or 6-wire, with or without a shield for terminal units. For conduit type units there can be 2- wire or 3-wire, plus ground. It is important to know the number of wires and the presence of a shield or ground in order to specify the current loop unit. Also it is important to confirm the voltage is 24 VDC, that it is a 4-20 mA current loop and not just a 24 VDC relay circuit or a digital data circuit, and the type of enclosure required fir the environment where it will be applied.
What are they used for:
- Measure water or other liquid flow rate past a given point.
- Measure liquid or gas pressure.
- Measure liquid or dry material level in a tank
- Measure weight on a scale or load cell
- Measure heat level
- Measure speed of a production line
- Measure the volume or pressure in a pipe transporting liquid or gas.
CONCLUSION
A Current Loop Surge Protective Device at one, or both ends of that circuit is often the difference between continuous, accurate, available measurements, or constant downtime and parts replacement.