How Clamp Meters Work: 3 Listings Compared

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A clamp meter reads current without breaking the circuit, because its jaw opens around one conductor. This page explains that idea with three clamp meter listings from one search, and it uses only what each listing states. As general background, the magnetic field around a conductor carrying current is what the jaw senses, so the jaw is closed around a single wire at a time. The listings do not explain the sensing method, and the figures below are the ones each seller gives. Listings were checked on 11 October 2026.

Quick answer

A clamp meter reads current by closing its jaw around one conductor. The Klein Tools CL120 is an auto-ranging AC clamp rated to 400 amps, with non-contact voltage testing in the jaw. The Fieldpiece SC260 is a compact HVACR clamp multimeter with true RMS, temperature and capacitance readings. The FNIRSI DMC-100 is the only clamp meter here whose listing states AC and DC current up to 600 amps, and it adds a real-time curve recording. If you need DC current, only the FNIRSI listing states it.

Comparison table

Listing (ASIN)	Current stated	Other functions stated	Included as listed	Display or count stated
Klein Tools CL120 (B08CP6GL49)	AC, auto-ranging up to 400 A	AC and DC voltage, resistance and continuity through test leads; non-contact voltage in the jaw	Digital clamp meter, AC auto-ranging 400 A	Backlit LCD; count not stated
Fieldpiece SC260 (B00KLYJG78)	AAC readings; range not stated in bullets read	True RMS volts, temperature, capacitance, non-contact voltage, continuity warning, diode test	Meter only	Backlight; count not stated
FNIRSI DMC-100 (B0DP2L9CFR)	AC and DC up to 600 A	Voltage, resistance, capacitance, frequency, temperature, non-contact voltage	Clamp meter, two multimeter pens, temperature probe, Type-C cable	9999 counts in title; 10000 counts in bullets

How we chose these listings

The search returned several listings that name a clamp meter, and this page keeps the three whose title or item type is a clamp meter. Several other results were digital multimeters or energy meters. The energy meters measure kilowatt-hours on a home or RV supply, and a clamp meter is not the same tool, so they are left out. The multimeters without a clamp are also left out. The figures below come from the titles, bullets and specification fields. Where two fields disagree, both values are shown.

How to read a clamp meter listing

A clamp listing has four figures that matter most. The first is the current range, because the jaw can only measure current up to the rating on the listing. The second is whether the current is AC only, DC only or both, since a listing that gives only AC cannot measure a DC source. The third is the voltage and safety category, which should be stated on the product page for the work you plan to do. The fourth is the extra functions. Some clamps read voltage, resistance and continuity through test leads, while others read them through the jaw or a separate pen.

• Current range: the maximum current the jaw is rated for.
• AC or DC: the type of current the listing states.
• Voltage and category: the voltage range and the safety category on the product page.
• Extra functions: the leads, pens and sensors the listing names.

1. Klein Tools CL120 Digital Clamp Meter, Auto-Ranging 400 Amp AC (B08CP6GL49)

The Klein CL120 measures AC current through its clamp, with auto-ranging technology that the listing says selects the range for accurate results. The bullets say it also measures AC and DC voltage, resistance and continuity through its test leads. A non-contact voltage tester is built into the clamp jaw, and the LCD is backlit for low-light readings. The specification field lists the measurement types as ammeter, voltmeter and ohmmeter. The item weighs 9.76 ounces and measures 8.45 by 3.51 by 1.51 inches. The warranty is listed as see manufacturer website, and the model is CL120. A safety field mentions CAT III and CAT IV caps, which is the category wording the listing uses.

View the Klein CL120 listing on Amazon

2. Fieldpiece Compact HVACR Clamp Multimeter SC260 (B00KLYJG78)

The Fieldpiece SC260 is described as a compact clamp meter for electrical HVACR service in hot and cold environments. The bullets give true RMS readings for volts and amps, with a backlight. Temperature and capacitance readings are listed, and the meter has a non-contact voltage function and an amperage reading. The bullets also list a continuity warning and a diode test. An auto select mode detects whether the meter is measuring capacitance or resistance without a manual setting. The item dimensions are 3.5 by 3 by 9.1 inches. The specification field gives an item weight of 0.27 g, which does not fit a handheld meter, so check the weight on the product page. The included items are the meter alone.

View the Fieldpiece SC260 listing on Amazon

3. FNIRSI DMC-100 Clamp Meter 9999 Counts TRMS, 600A AC/DC (B0DP2L9CFR)

The FNIRSI DMC-100 is the only listing here that states both AC and DC current, with a range up to 600 amps. The bullets say it reads AC and DC current, voltage, resistance, capacitance, frequency and temperature in TRMS mode, and that it has non-contact voltage detection. The title gives 9999 counts, and a bullet gives 10000 counts, so the count is shown as stated in both places. The listing includes a real-time curve recording feature that stores 8 sets of real-time data and 30 sets of historical records. The display is a 2-inch color screen with 10 brightness levels and a choice of dark or light theme. The battery is a rechargeable 1500 mAh lithium cell charged through a Type-C cable. The item weighs 6.72 ounces and measures 7.7 by 2.91 by 1.14 inches.

View the FNIRSI DMC-100 listing on Amazon

Worked example: a 450 amp reading against the listed ranges

Suppose a motor circuit draws 450 amps at start-up. This is a figure chosen for the example, and it is not from any listing. The Klein CL120 is rated for AC up to 400 amps, so a 450-amp reading is above its listed range and it would not be a valid reading for that tool. The FNIRSI DMC-100 is rated for AC and DC up to 600 amps, so 450 amps falls inside its listed range. The Fieldpiece SC260 lists AAC readings, but the bullets read here do not give a maximum current, so check its range on the product page before using it on a load of that size.

The same example shows why the current type matters. If the source were DC, the Klein listing would not be a match, because its stated current is AC. The FNIRSI listing states both AC and DC, so it would fit that case within its 600-amp range.

What we could not verify

The listings do not give a safety category for the Fieldpiece or the FNIRSI in the fields read, and the Klein category is given as caps rather than a plain rating, so check each category on the product page. The Fieldpiece weight conflicts with its size and type. The FNIRSI count is 9999 in the title and 10000 in a bullet. The listings do not compare accuracy across the three meters, so this page cannot rank them on accuracy. The claims about the Klein’s built-in voltage tester and the FNIRSI’s curve recording are listing statements that this page does not confirm.

Frequently asked questions

Can a clamp meter measure DC current?

Only the FNIRSI DMC-100 listing states DC current, up to 600 amps. The Klein CL120 is listed as AC current, and the Fieldpiece SC260 lists AAC readings in its bullets. Check the current type on the product page before you buy.

Can a clamp meter measure voltage as well?

All three listings state a voltage function. The Klein CL120 measures AC and DC voltage through its test leads, the Fieldpiece SC260 lists true RMS volts, and the FNIRSI DMC-100 lists voltage with simultaneous display of voltage and current.

Which of these reads capacitance?

The Fieldpiece SC260 and the FNIRSI DMC-100 both list capacitance. The Klein CL120 specification field lists ammeter, voltmeter and ohmmeter, and its bullets do not mention capacitance.

Do these include a non-contact voltage function?

All three do. The Klein CL120 builds a non-contact voltage tester into the jaw, the Fieldpiece SC260 lists non-contact voltage readings, and the FNIRSI DMC-100 lists non-contact voltage detection.

Which one records data over time?

The FNIRSI DMC-100 is the only listing that describes data recording. It stores 8 sets of real-time data and 30 sets of historical records. The other two listings do not describe recording in the bullets read.

Conclusion

For a clamp meter that reads AC current up to 400 amps with non-contact voltage in the jaw, the Klein CL120 is the listing that states those figures. For compact HVACR work with temperature and capacitance, the Fieldpiece SC260 is the listing built for that job. For AC and DC current up to 600 amps with data recording, the FNIRSI DMC-100 is the only one here that states both. Check the safety category and the weight on each product page before you buy. For more on clamp choice, see best true RMS digital clamp meter, best AC and DC current clamp meter and best handheld clamp.

Listings on Amazon: Klein CL120, Fieldpiece SC260, FNIRSI DMC-100.