The usual reasons for these uncertain results are electrical noise or high levels of harmonics. One possible solution is to link out the RCD protection and carry out a high current loop test. This is not generally acceptable, however, as faults can be introduced during reconnection after testing and additional safety precautions are required.

Fortunately, there’s now a better way. A multifunction installation tester (MFT) has been developed that provides dependable non-trip loop testing on “difficult” circuits and also saves time on unproblematic circuits.

Because non-trip loop tests can be influenced by noise, conventional testers make multiple measurements and display the average of the results. The new MFT does the same but, instead of simply calculating an average, it uses modified hardware and a unique algorithm that takes into account noise and harmonics, thereby delivering dependable results even in difficult conditions.

The new MFT has a built-in confidence display. When a loop test is initiated, this shows a broad arc. As the instrument homes in on a dependable result, the width of the arc decreases until it is just a single dot. On quiet circuits, getting a high-confidence “single dot” result takes as little as eight seconds, compared with the customary 15 seconds.

On noisy circuits, the confidence arc takes longer to diminish to a single dot and if the circuit is very noisy, the arc may open out again before shrinking to the dot. Nevertheless, you still save time because the result is “right first time”!

Non-trip loop impedance testing has moved on! The old problem of strange and varying results has been solved with an innovative instrument that saves time for its users whether the circuit under test is noisy or quiet.

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