Functional Devices offers a wide variety of current sensors (split & solid core switches, transducers). Selecting the wrong model is a common mistake. This most frequently happens with the RIBXG and RIBXGH series of current sensors. Let’s compare model RIBXGTA and RIBXGHTA for a better understanding of the differences between the series.
Looking at the table above, we can see that both models have a sensing range of 0.75 – 150 A, are split cores, and adjustable thresholds. The key difference is in the contact ratings and what those contacts do with and without a load.
A common application for our current sensors is to interface to a building automation system (BAS) to know if certain loads are on or off. This is typically done via a dry-contact closure, and the RIBXGTA is an excellent choice. Model RIBXGHTA however would not work as expected.
Once the load current being monitored exceeds the threshold, the RIBXGTA will close its contacts and function perfectly as a dry-contact output for the BAS.
Model RIBXGHTA would also close its contacts, but without a load would measure approximately 250 ohms. This resistance causes the BAS to not register the dry-contact closure, giving a false indication that the load is off. This resistance is normal though, as the RIBXGHTA was designed to control 120 Vac loads.