Multimeter Test Leads: CAT Ratings and Probe Tips

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Match category, voltage and currentSafety ratings. Choose tips, insulation and plugsConstruction.

Match the measurement category, voltage and current ratings

Fluke's TL175 TwistGuard test leads are rated CAT II 1000 V, CAT III 1000 V and CAT IV 600 V, 10 A maximum, at pollution degree 2, and are stated to conform to EN 61010-031. The adjustable tip shroud shows the category rating that applies to the tip exposure in use. [1]

Amprobe's TL36A test lead set is rated CAT IV 600 V and CAT III 1000 V. [2]

Editorial note: in both examples the CAT IV voltage rating is lower than the CAT III rating, so check the rating for the category of the circuit you will measure, not only the highest voltage printed on the lead.

Give the supplier the instrument model and its input jacks, the measurement categories and voltages of the circuits to be measured, the maximum current, the probe tips and clips needed, lead length, insulation material, operating temperature range and the safety standard the set must conform to.

Choose probe tips, insulation, plugs and length

The TL175 lets the user twist the lead to change the exposed probe tip length from 19 mm to 4 mm. Its silicone insulation has a two-colour wear indicator: if the inner white layer shows through the outer black layer, the leads must be replaced. It uses universal input plugs for instruments that accept standard 4 mm shrouded banana plugs, its strain relief is tested to 30,000+ bends without failure, and its environmental ratings are −20°C to 55°C at up to 2000 m altitude; a TL175E version includes removable 4 mm lantern tips. [1]

The TL36A set has two vinyl lead wires, two threaded probe tips and two threaded alligator clips that screw onto the probe tips; the leads are 48 inches long with the clips attached, and the 2.67-inch clips have a 0.30-inch jaw opening with teeth that grip the conductor for a hands-free connection. [2]

Editorial calculation: 48 inches is about 1.22 m (48 × 25.4 mm = 1,219 mm), and a 0.30-inch jaw opening is about 7.6 mm. [2]

HIOKI's L9300 leads take a different route to tip length: the safety cap is built into the probe, not a separate cover. In the rear position it exposes a longer, slender tip for narrow terminals or PCB test points; for CAT III 1000 V and CAT IV 600 V work it slides forward to cut the exposed contact length, and it locks in each position. The set has angled 4 mm safety banana plugs and finger guards, is rated CAT II 1000 V, CAT III 1000 V and CAT IV 600 V and up to 10 A, is 95 cm long, and is listed at 1,110 mm and 0.075 kg packaged. [4]

Accessory tips carry their own, lower ratings. HIOKI lists the L4934 small alligator clips that fit the L9300 at 3 A maximum, CAT II 600 V and CAT III 300 V for conductors 2 to 4 mm in diameter, and the L4933 extra-thin contact pins at 3 A maximum and 60 V DC / 30 V AC. Editorial calculation: fitting the L4934 clips drops the usable CAT III rating from 1000 V to 300 V and the current from 10 A to 3 A, so the rating that applies is the lowest of lead, accessory and meter. [4]

Check leads against the HSE GS38 guidance

The UK Health and Safety Executive's guidance note GS38 (fourth edition, 2015), Electrical test equipment for use on low voltage electrical systems, says test probes, clips and leads should conform to BS EN 61010-031 (or BS EN 61243-3 for two-pole voltage detectors), be marked with their rated category CAT II, III or IV and the maker's name or mark, and have finger barriers or a shape that guards against hand contact with the conductors under test. [3]

GS38 lists incidents linked to inadequately insulated or damaged leads, removed insulation, leads falling off meter terminals, long intertwined leads, leads severed by a closing cabinet door, and use beyond the leads' CAT rating, for example CAT II equipment on a CAT III installation. It describes CAT IV as the source of the installation, CAT III as the building installation and CAT II as circuits connected to it such as appliances. [3]

Editorial calculation: a 2 Ω fuse resistance in a lead pair is a 200% error on a 1 Ω continuity reading unless the meter is zeroed with the leads connected.

GS38 point	Guidance
Exposed metal tip	Not exceeding 4 mm across any surface; 2 mm or less, or spring-loaded retractable screened probes, strongly recommended where practicable
Fusing with a multimeter	High-breaking-capacity (HBC/HRC) fuse, rated up to 500 mA in GS38's guidance; 10 A cited for loop impedance or RCD testers; or a current-limiting resistor and fuse
Fuse resistance	Low-current (500 mA) fuses can add up to 2 Ω to the lead; glass fuses are not suitable
Lead insulation and sheath	Adequately insulated for the environment and sheathed against mechanical damage
Colour	Leads coloured so one can be told from the other
Length	Long enough for the purpose but not unwieldy
Exposed conductors	None other than the probe tips, including if a lead becomes detached

State the highest measurement category and voltage of the circuits you test, whether fused leads are required, and the maximum exposed tip length, and ask for the lead set's EN 61010-031 rating and fuse type.

Probe tip, insulated wire, strain relief, banana plug and clips

Each part has its own limit: the wire's insulation carries the wear indicator, the plug has to fit the meter's jacks, and HIOKI's add-on clips and pins are rated below the lead they fit. [1] [4]

Part	Role	Fix in the order
Probe and tip	Contact the circuit. [1] [2]	Exposed tip length; shroud.
Lead wire and insulation	Carry the signal and insulate the user. [1] [2]	Material; wear indication.
Strain relief	Protect the wire at the probe and plug. [1]	Bend test.
Input plug	Connect to the meter. [1]	4 mm shrouded banana or other.
Accessory tips and clips	Adapt to sockets or hands-free connection. [1] [2]	Lantern tips; alligator clips.
Accessory clips and pins	Hands-free or fine-pitch contact; rated separately, e.g. 3 A, CAT III 300 V. [4]	Rating of each accessory.

Category voltage, current, tip exposure, fusing and plug for a lead set order

Conductor cross-section, contact resistance, insulation resistance, ingress protection and set weight have no published value in the sources reviewed, so the supplier has to state them; the last row carries the GS38 limits of 4 mm exposed tip and a fuse of up to 500 mA. [3]

Field	What it means and published values	Ask the supplier for
Rated Voltage	By category, e.g. CAT III 1000 V, CAT IV 600 V. [1] [2]	Rating per category and accessory.
Rated Current	E.g. 10 A maximum. [1]	Max current.
Conductor Cross-Section	Wire size inside the lead.	Value.
Cable Length	E.g. 48 in with clips. [2]	Length.
Contact Resistance	Resistance of the lead set.	Value.
Insulation Resistance	Insulation quality of the lead.	Value.
Dielectric Strength	Insulation withstand per the safety standard. [1]	Standard conformity; test report.
Operating Temperature	E.g. −20°C to 55°C. [1]	Range.
Ingress Protection	Protection against dust and water.	Rating if needed.
Probe Tip Diameter	Tip size and exposed length, e.g. 19 mm to 4 mm exposed. [1]	Diameter; exposed length.
Connector Type	E.g. 4 mm shrouded banana plugs. [1]	Plug type to suit meter.
Cable Insulation Material	E.g. silicone; vinyl. [1] [2]	Material.
Weight	Set mass.	Value.
Exposed tip and fusing	Tip ≤4 mm (2 mm recommended); HBC fuse up to 500 mA with multimeters per HSE GS38. [3]	Tip length; fuse rating and type.

Send the meter, circuit and accessory data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Meter: [model; input jack type]
Circuits: [measurement categories; voltages]
Current: [maximum]
Tips: [exposed length; lantern tips; clips]
Lead: [length; insulation material]
Environment: [temperature]
Standard: [safety standard conformity]
Volume: [sets]

See manufacturer records Send an enquiry through CNFX

Buyer questions

What CAT rating do multimeter test leads need?

A rating for the category and voltage of the circuit measured; one set is rated CAT II 1000 V, CAT III 1000 V and CAT IV 600 V. [1]

Why do some probes limit exposed tip length?

One design adjusts exposed metal from 19 mm to 4 mm and shows the category rating that applies to the tip exposure in use. [1]

When should test leads be replaced?

One silicone lead has a wear indicator: if the inner white insulation shows through the black outer layer, the leads must be replaced. [1]

How much bare metal should a test probe tip have?

HSE guidance GS38 says no more than 4 mm across any surface, and strongly recommends 2 mm or less, or spring-loaded retractable screened probes, where practicable. [3]

Do alligator clips change a test lead's rating?

Yes: HIOKI rates its L9300 leads CAT III 1000 V and 10 A, but the L4934 clips that fit them are rated CAT III 300 V, CAT II 600 V and 3 A. [4]

Sources and what still needs a direct check

Sources checked 2026-10-12. The Fluke, Amprobe and HIOKI sources are makers' product pages for specific test lead sets, cited as examples of the parameters a test lead specification covers, not endorsements; HSE guidance note GS38 sets out UK safety guidance.

Still to check yourself

Match CAT rating to each circuit.
Check accessory tips keep the rating.
Confirm current rating.
Match plugs to the meter.
Verify the legal supplier and factory.

Test leads for multimeters