How to look after your test leads and probes (and stop losing tips)

Your test leads and probes get more abuse than almost anything else in the bag. They get dragged across floors, shut in board doors, chucked in the van and buried under everything else. They're also the bit between you and whatever you're testing, so it's worth five minutes to look after them properly.

What the guidance actually says

The main reference is HSE guidance note GS38, Electrical test equipment for use on low voltage electrical systems (fourth edition). It sits under the Electricity at Work Regulations 1989. GS38 summarises the regulations as requiring equipment, so far as is reasonably practicable, to be constructed, maintained and used in a way that prevents danger.

BS 7671 tells you which tests to do and requires instruments that meet BS EN 61557 (Regulation 643.1, see Best Practice Guide 7). It doesn't cover how you store or carry your leads. For that, GS38 is the document to know.

Probes and clips (GS38)

• Conform to BS EN 61010-031, or BS EN 61243-3 for a two-pole voltage detector.
• Marked with the CAT rating (II, III or IV) and the manufacturer's name or mark.
• Finger barriers, or shaped to stop your hand slipping onto the conductor under test.
• Exposed metal tip no more than 4mm. GS38 strongly recommends 2mm or less where practicable, or spring-loaded retractable screened probes.

Leads (GS38)

• Adequately insulated, and coloured so one lead can be told from the other.
• Flexible, with enough capacity for the job.
• Sheathed against mechanical damage.
• Long enough for the job, but not so long they're clumsy.
• No exposed conductors other than the probe tips.

Check them before every job

GS38 lists the common defects to look out for:

• Cracked cases
• Damaged insulation: abrasion, cuts or perished flex
• Loose terminals
• Damaged spring-loaded covers on probe tips

It's blunt about damaged leads too. Leads with visible damage, cracking, fraying or cut insulation, or with normally insulated metal exposed, should be discarded and replaced, not taped up. It also flags leads contaminated with conductive material, and leads sheared by a cabinet door being closed on them.

GS38 also says test equipment, including kit issued to individuals, should be maintained by a competent person. Keep records of inspections, especially where faults are found.

Fused leads: know what they do to your readings

If you use fused leads, GS38 notes that fuses, especially low-current 500mA ones, can add significant resistance to a test lead, up to 2 ohms. Allow for that when you're measuring resistance. When you replace a fuse, use the correct type and rating. GS38 says glass fuses aren't suitable.

Day-to-day habits that save your leads

None of this is in a regulation. It's just what works on site:

• Keep the tips together and off the floor. Loose probes and crocs end up under kneeling pads, in the bottom of the bag, or left in a socket box.
• Don't let probes rattle round the bag. Tips knocking against tools is how they get bent or damaged.
• Coil leads loosely. Don't wrap them tight round the tester.
• Watch board doors and covers when leads are run through them. That's GS38's shearing point in real life.
• Null your leads when you swap probes or crocs, so you're not carrying lead resistance into your continuity readings.
• Keep a spare set so a damaged lead goes in the bin, not back in the bag.

Tired of messy leads?

That's the problem Tip-Clip was made for. It locks onto your probe tips and clips onto your tester strap or tool belt. Your probes and crocs stay in one place, protected from getting knocked about, and ready for the next test instead of tangled in the bottom of the bag. It holds up to five tips and is designed for standard 4mm probe ends. We've fitted it to Fluke, Megger, Kewtech, Di-Log and Martindale probes.

It won't make a damaged lead safe. Nothing does, and GS38 says bin it. What it does is stop good leads getting damaged and lost in the first place.

Tip-Clip Test Probe Holder. Made in the UK.