Home / Clamp meter vs multimeter: which one an apprentice electrician buys first

Clamp meter vs multimeter: which one an apprentice electrician buys first

Fluke describes a digital multimeter as "essentially a voltage-measuring tool with some current abilities" and a clamp meter as "basically a current-measuring tool with some voltage abilities" [1]. Which one an apprentice buys first depends on the work in front of them. This guide explains what each instrument measures, what the safety ratings mean, and which spec lines separate one model from another, using the makers' published specs for meters on this site as worked examples. It is a researched explainer, not a hands-on test.

Current: through the jaws or through the circuit

A clamp meter reads current by closing its jaws around one conductor, so Fluke notes it measures current "without breaking the circuit" [1]. A multimeter reads current in line: you open the circuit and the current flows through the meter's own input, and Fluke says a multimeter's current range is "usually limited to less than 20 amps" [1]. The Fluke 117 and the Klein MM720 each publish a 10 A AC and DC current maximum [8][17]. The Fluke 323 and 325 publish 400 A AC through the jaws, and the Klein CL900 publishes 2000 A AC and DC [10][12][16].

DC current through the jaws is a separate feature, not a given. Fluke says the 325 "measures AC/DC current up to 400 A through jaw", while the spec tables for the 323 and 324 list no DC current range [10][11][12]. If you will measure DC loads, look for a DC current line in the spec table.

The jaw sets the largest conductor or bundle you can close around. Fluke lists a maximum wire diameter of 30 mm (600 MCM) for the 323, 324 and 325; Klein lists a 1.38 in jaw for the CL800 and a 2 in jaw for the CL900 [10][11][12][15][16].

Voltage, resistance, continuity and the other dial positions

Both instruments read AC and DC voltage through test leads. The difference Fluke draws is resolution: a multimeter reads "in milliunits", while a clamp meter "usually measures to the nearest tenth or hundredth of a unit" [1]. The resistance ranges show the same split: the Fluke 117 publishes ranges up to 40 megohms, and the Fluke 323 publishes 400.0 ohm and 4000 ohm ranges [8][10].

CAT ratings: what CAT III 600 V and CAT IV 600 V mean on a job site

Fluke explains that IEC 61010 "establishes Measurement Category (CAT) and voltage ratings for electrical environments", and that "a higher CAT number refers to an electrical environment with higher power available and higher energy transients" [2]. Fluke also notes that NFPA 70E references the ANSI IEC 61010-1 standard that defines test tool category ratings [3]. Fluke's partial list of the categories:

Reading the rating on a real meter

The voltage after the category is the working voltage the meter is rated for in that location. The Fluke 117 is marked CAT III 600 V only [8]. The Fluke 87V, Klein MM720 and Klein CL900 are marked CAT III 1000 V and CAT IV 600 V, so each also carries a rating for the service entrance and meter base [9][16][17]. The Fluke 323, 324 and 325 are marked CAT III 600 V and CAT IV 300 V [10][11][12].

The leads are part of the rating. Fluke's application note says to confirm that "the DMM and test leads are rated for the category and voltage level" of the environment, and notes that a CAT II measurement can have up to 19 mm (0.75 in) of exposed metal on the test lead while a CAT IV measurement allows no more than 4 mm (0.16 in) [4]. Fluke's lead instructions say not to exceed the CAT rating of "the lowest rated individual component" of a product, probe or accessory [5]. Klein lists "Test Leads with CAT III/CAT IV Safety Caps" in the MM720 box [17].

Fluke adds that the IEC and NFPA do not enforce their test tool standards, so look for a label showing certification by at least one independent testing agency [2].

True-RMS vs average-responding

Fluke explains that an average-responding meter "uses averaging mathematical formulas to accurately measure pure sinusoidal waves" and reads non-sinusoidal waves only "with uncertain accuracy", while a true-RMS meter "can accurately measure both pure waves and the more complex non-sinusoidal waves" [6]. Fluke puts the error of an averaging meter on distorted waves at "up to 40% low or 10% high" [6].

The makers publish true-RMS for the Fluke 117, 87V, 323, 324 and 325 and the Klein CL800, CL900 and MM720 [8][9][10][11][12][15][16][17]. On a model not listed here, look for the words True-RMS or TRMS in the spec table, not only on the box.

Inrush, VFD filters and the advanced modes

Fluke defines inrush current as "the surge or momentary burst of current" that flows into a device when it is first powered on, and says it "can be 4 to 10 times greater than the normal running current, depending on the type of motor" [7]. The breaker or overload does not trip on it because both work on a time-versus-current curve [7]. Fluke states that "only meters that offer an inrush button can measure inrush current" [7]. On this site, the Klein CL900 lists a "dedicated mode for capturing Inrush Current" and the Fluke 376 FC lists inrush measurement "to filter out noise and capture starting current" [13][16]; the Fluke 325 page lists no inrush function [12].

For the output of a variable frequency drive (VFD), Fluke says advanced meters use signal processing, and that "you might need a low-pass filter to eliminate electronic interference that could distort readings" [1]. The Fluke 87V "supports accurate measurements on VFDs using a low-pass filter", and the Fluke 376 FC lists a "VFD low pass filter for accurate measurements of non-linear signals" [9][13].

Resolution is not accuracy: a datasheet example

Resolution is the smallest step the display shows. Accuracy is how far the reading may be from the true value. Fluke publishes the 117's 600.0 V DC range with 0.1 V resolution and an accuracy of +/-(0.5% + 2), where the table heading defines the terms as "[% of reading] + [counts]" [8].

Worked through for a 120.0 V DC reading (our arithmetic, not a Fluke figure): 0.5% of 120.0 V is 0.6 V, and 2 counts at 0.1 V resolution is 0.2 V, so the true voltage may be anywhere from 119.2 V to 120.8 V [8]. The display resolves 0.1 V; the specification allows 0.8 V either way. For comparison, Fluke publishes +/-(0.05% + 1) DC voltage accuracy for the 87V [9].

Display counts set the resolution on each range. Fluke lists a 6,000-count display for the 117, and 6,000 counts with 19,999 counts in high-resolution mode for the 87V; Klein lists a 6000-count LCD for the MM720 [8][9][17].

Which comes first, by type of work

There is no single answer, and your employer or apprenticeship program may set a required tool list, so check that first. What follows describes which spec lines apply to which work, using the makers' own descriptions.

Multimeters used as examples

Each model page lists the maker's full spec table, the box contents and the date the figures were checked.

Clamp meters used as examples

Fluke marks the 324 as discontinued and suggests the 325 [11]; Klein marks the CL800 "no longer in production" [15]. Both stay listed here because their pages show the spec lines discussed above.

What to check in the spec table

Sources

  1. Clamp Meters vs Multimeters (Fluke). Retrieved 2026-10-26; published spec.
  2. Electrical safety standards (Fluke). Retrieved 2026-10-26; published spec.
  3. IEC Category Ratings: Use the Right Tools for the Job (Fluke). Retrieved 2026-10-26; published spec.
  4. Application Note: Testing your test leads for electrical measurement safety (Fluke). Retrieved 2026-10-26; published spec.
  5. TL1500DC Test Leads Instruction Sheet (Fluke). Retrieved 2026-10-26; published spec.
  6. What is true-RMS? (Fluke). Retrieved 2026-10-26; published spec.
  7. How to Measure Inrush Current (Fluke). Retrieved 2026-10-26; published spec.
  8. Fluke 117 Electrician's Multimeter (product page and specifications) (Fluke). Retrieved 2026-10-26; published spec. The 120.0 V worked example on this page applies this DC accuracy figure; the arithmetic is ours (calculated estimate).
  9. Fluke 87V Industrial Multimeter (product page and specifications) (Fluke). Retrieved 2026-10-26; published spec.
  10. Fluke 323 Clamp Meter (product page and specifications) (Fluke). Retrieved 2026-10-26; published spec.
  11. Fluke 324 Clamp Meter (product page and specifications) (Fluke). Retrieved 2026-10-26; published spec.
  12. Fluke 325 Clamp Meter (product page and specifications) (Fluke). Retrieved 2026-10-26; published spec.
  13. Fluke 376 FC True-RMS Clamp Meter (product page and specifications) (Fluke). Retrieved 2026-10-26; published spec.
  14. Fluke 902 FC HVAC Clamp Meter (product page and specifications) (Fluke). Retrieved 2026-10-26; published spec.
  15. Klein Tools CL800 Digital Clamp Meter (product page) (Klein Tools). Retrieved 2026-10-26; published spec.
  16. Klein Tools CL900 Digital Clamp Meter, 2000A (product page) (Klein Tools). Retrieved 2026-10-26; published spec.
  17. Klein Tools MM720 Digital Multimeter (product page) (Klein Tools). Retrieved 2026-10-26; published spec.

Researched by Rob, licensed electrician (Australia), 18 years on the tools. Researched from the makers' published US product pages, application notes and safety pages listed under Sources, each retrieved on the date shown; each meter's own page carries its full spec table with the date checked. This page describes what the makers publish. It does not rank meters and it is not a substitute for the lockout, PPE and NFPA 70E work practices the job requires. Found an error? Tell us.

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