What features are a must have on a multifunction tester?

[DPG]

Second the above, also get an On site guide, IMO the easiest to understand is from "unite the union" cover says "The Electricians Guide to Inspection and Testing" Based on BS76712018 saying all that the "IET On-site Guide" is a ring bound volume and easier to use as it will not keep closing up on you when referencing anything, unlike the Unite version.

Yes, that's a pet hate of mine - guides printed in such a format that you need an industrial press to keep them open.

The IET version with spiral binding is much better.

 

[pc1966]

Another thumbs-up for both the Guidance Notes #3 and the On-site guide. GN3 covers a lot of how & why of testing, and also has some notes on types of test equipment and real-world accuracy to expect, a very useful thing to have read cover-cover at one point for background info.

The OSG is also one of those useful books as it has tables of common circuit limits (e.g. how long you can run XYZ cable on ABC protection, etc) and the Zs limits for testing for common fuses and circuit breakers. It also has handy tables not in the regs for stuff like recommended spacing of cable support clips, etc.

Ideally you want a MFT so only one box to keep an eye on and feed batteries from time to time. That and a volt tester/proving unit would be your basic test kit. Typically you need:

• Low ohm for earth bonds, R1+R2, etc
• High ohm at 250V and 500V for insulation testing.
• AC volts for checking supply in-spec
• Zs/PFC for supply characteristics and end of circuit check against fuse/MCB values
• RCD trip times for at least 30mA (final circuit) to 300mA delay (incomer TT, or farm fire protection). You should have at least type AC and type A RCD test available, but type B is needed for some cases now (photovoltaic protection, some EV chargers)

Generally get the best MFT you can afford that ticks the list you need now and maybe in 2-5 years. As already mentioned, auto-RCD is a massive help, you connect up and then just keep resetting the breaker, finally copying the numbers down, or if really fancy saving to PC/laptop/tablet for form-filling.

To begin with I would say you ought to write down values, what you tested, where you did it and any other info like date, etc, in a small note book or diary. Helps sometime!

Other stuff if you look to do commercial work is the earth rod check already mentioned. If you have a supply you can check this using the Zs method, but if installing / commissioning without a safe/dependable supply then you need one that can use earth spikes to measure the rod.

Another MFT feature on some is 3-phase rotation checking and allowing you to measure PFC phase-phase which is handy if end of a long line with delta load and no neutral!

 

[pc1966]

Just to add, sometimes a multimeter is handy for checking things but not for proving dead!

Typically they offer AC & DC volts, AC & DC current down to microamps, ohms from typically 1 ohm to 10M (especially in the 100-100k range that MFT don't do well), continuity bleeper, diode check, sometimes frequency and capacitance. Not #1 things for typical electrical work but sometimes for looking at faulty accessories, checking batteries, or working on car electrics, etc.

If looking to get a meter then make sure it is rated to at least CAT III 400V so it won't explode in your face if you make a mistake one day (e.g. measuring amps instead of volts on high current circuit). The safety of electrical test equipment is covered by HSE note GS38 and you will sometimes find that mentioned on spec sheets:

https://www.hse.gov.uk/pubns/priced/gs38.pdf

I have a few multimeters myself including an accurate but expensive Fluke 179, but the one that folks on here seem to like best is the Testo 760-1 or its slightly better -2 brother, as the auto-range aspect reduces common mistakes.

Another occasionally handy thing is a clamp ammeter, allows checking AC loads without disconnecting wires and not much risk of burning it out if the load turns out be faulted at kA values. If looking for one for most work, I would get one covering 200A or so max but also going down to mA resolution for checking earth leakage currents. The likes of the HandyMAN TEK775 seems best value, or the (probably identical but better known branded) DiLog DL6518. Of course you can pay up to £500 for fancier or more accurate ones, but my DL6518 has proven OK for the times I needed it.

 

[nickstig]

Hey everyone,

Thanks for all the responses and recommendations. Some really useful information there, especially on which books are useful for testing. Thanks a lot.

Nick