Measurement frequency switching on earth testers

QThe Earth HiTester 3151 has frequency switch settings such as 3a and 3b. What are these? Which should I use in normal measurement?


Use of inverters that utilize semiconductor control elements has surged recently in manufacturing plants and other facilities, leading to an increase of cases in which leak currents flowing to grounding lines include not only fundamental components as in the past, but also numerous harmonic components. When measuring grounding lines that remain connected, for example during maintenance inspections, harmonic current leaking from equipment may prevent indicated values from stabilizing. Two frequencies are provided so that it is possible to limit interference with harmonic currents by switching the frequency being measured in such situations and thereby allow stable measurement (575 Hz and 600 Hz). If the indicated value fails to stabilize, try switching the frequency.