Non-contact pen
A first look. Finds live cables and broken conductors. Never the last word.
Chest pocket and pouch
Know it's dead, then prove it
Three testers earn a place in the pockets. Each answers a different question, and only one of them proves a circuit dead.
Two-pole indicator
The proving tool. Simple output, shrouded probes, built for isolation.
Pocket multimeter
For numbers: control voltages, continuity, a quick reading.
Meter notesTwo jobs, two testers
A non-contact voltage tester answers one question: is there an AC electric field near this conductor? A two-pole voltage indicator answers a different one: is there a dangerous voltage between these two points? Mixing them up is how people get hurt. In the pocket map, the pen lives in the chest pocket because you reach for it all day. The two-pole indicator lives on the pouch edge, close enough to grab but never confused with the pen.
What a non-contact tester is good for
Use it for a first look: tracing which cable in a back box is live, checking a socket before you pull it off the wall, finding a broken conductor in a flex. Run it past a known live source before every use so you know it still sounds. Learn its limits. Screened or armoured cable, a tester held at the wrong angle, a weak battery or a deep back box can all hide a live conductor. A silent pen is not a dead circuit. The Fluke 1AC II VoltAlert and the Klein Tools NCVT-3 are common examples of the type. Both are fine as a first look and neither is a proving device.
Two-pole indicators: the one you prove with
Safe isolation under the Electricity at Work Regulations 1989 depends on proving, and the HSE's GS38 guidance describes what suitable test equipment looks like. Look for shrouded probes with no more than 4 mm of exposed tip (2 mm where practicable), finger barriers, and fused leads if the instrument is a meter. A dedicated indicator such as the Fluke T150, or a Martindale voltage indicator used with its proving unit, is built for this job. The output is simple, there is no range switch to get wrong, and the casing is made for site knocks.
Prove, test, prove
- Inspect the indicator, leads and probes. Do not use anything damaged.
- Prove the indicator on a proving unit or a known live source.
- Test the circuit: line to neutral, line to earth and neutral to earth.
- Prove the indicator again on the same source.
- Lock off, label and keep the key on you.
Follow your procedure. Your employer's safe isolation procedure comes first. IET Guidance Note 3 and Electrical Safety First both publish widely used versions. This page is information, not training.
Pocket multimeters
A compact meter such as the Fluke 101, which is rated CAT III 600 V, earns its place when you need a number: a control voltage, continuity through a lamp circuit, a reading across a capacitor. It can prove dead when it has leads that meet GS38. Most crews still keep the two-pole indicator for isolation, because a dial left on the wrong range is a risk a fixed indicator never carries. Treat the meter as the thigh-pocket tool for diagnosis and the indicator as the pouch tool for isolation.
What to look for when you buy
- Rating plate: a CAT marking to IEC 61010 with a voltage that matches your work, such as CAT III 600 V.
- Probes: shrouded, with minimal exposed tip, as GS38 describes.
- Weather protection: an IP rating that survives drizzle and dust on site.
- Battery behaviour: a clear low-battery warning and an easy battery door.
- Markings: UKCA or CE, and a rating plate that matches the manual. Be wary of unmarked clones.
The brand names above are examples of the category, not endorsements. Whatever you carry, check it before each job and again if it has been dropped. A tester you have checked is worth more than a tester with a better badge.