The TPA earth resistance meters used to synchronize or trick RCD circuits by placing the gray probe on the phase and the green one on the grounding. However, in recent years, some manufacturers have reversed the internal circuit, requiring us to reverse the probe tips during measurements. It’s uncertain whether the installed model will trip or not.

If it trips, simply invert the probe tips of the TPA device, and it will not trigger. However, if it still trips even with the inversion of probe tips, it indicates a current leakage in the grounding system that needs correction. Therefore, TPA earth resistance meters can detect current leaks in systems equipped with RCDs.