CM100 AC/DC Current Clamp Meter

Detecting and resolving parasitic draws is tough. The CM100 makes finding these elusive ‘current leaks’ quick and easy. This tool will give you the ability to check on circuits, and prevent batteries from being drained.

The CM100 is the product of GTC’s extensive work and expertise in vehicle electronics and electrical systems. This clamp meter will give you precise information as soon as you put it around a wire, telling you exactly how much current is coming or going from a circuit. There’s nothing better than a milliamp-resolution clamp meter for working on low-voltage (<50V) current draws; conventional multimeters require interrupting the circuit, and add a voltage burden which prevents accurate measurement. The CM100 makes it easy to troubleshoot current draws, and give you confidence in dealing with troublesome electrical gremlins.

USD $252.50

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Who it’s For:

  • Automotive, marine, and heavy duty technicians who troubleshoot vehicle electronics and electrical systems
  • Aftermarket installers looking to test or troubleshoot new equipment
  • Technicians looking to test starter motors or large electrical loads like refrigeration units should look at our CM600.

What it Does:

Quickly and easily measures circuit current consumption, as well as voltages and resistances.

How it Works:

  1. Turn the unit on by turning the selector wheel to the mode of interest
  2. Position the CM100 near and parallel to the wire or cable, with the jaw closed
  3. Press the zero/tare button to compensate for interference
  4. Open the jaw, put it around the wire, and allow it to close
  5. Read the circuit’s AC or DC current consumption off the high-contrast liquid crystal display

Warranty & Support:

Covered by our standard 1-year warranty, and supported for much longer. Replacement parts and accessories are generally available for 10+ years.



  • Electronic and electrical circuits
  • Automobiles
  • Trucks
  • Trailers
  • Boats
  • RVs
  • All 0 to 100 Volt AC/DC powered circuits



The CM100 low current clamp meter is designed to accurately measure current, current leaks (parasitic draws down to 1mA) and electrical loads from 1mA to 100 amp AC/DC and voltages from 0 to 600 AC/DC. The CM100 can be used on electric motors, fuel pumps, charging systems, electrical circuits, etc.

The small diameter (½ inch or 13mm) and narrow jaw makes it ideal for use in confined spaces and on small gauge wires. Other features include up to 600 volt AC/DC voltage, resistance measurement functions, audible continuity test, display hold and peak detector.

  • ACCURATE MEASUREMENT: Measures electrical loads from 1mA to 100 amp AC/DC and voltages from 0 to 600 AC/DC.
  • EASY TO READ AND USE: Large 4 digit LCD display, one touch auto-zero, and audio feedback.
  • MULTI-PURPOSE: Check and troubleshoot grounds, voltage drops, currents in battery chargers, alternators, electrical loads, and more.
  • DURABLE: Rugged plastic enclosure, 50 hours battery life, with a carrying case for safe storage.
  • COMFORTABLE: Quality design offers comfortable handling, and a smaller jaw for ease of use.



CM100 CM600 CM1000
DC Current 0.001 to 100 A. 0.1 to 600 A. 0.1 to 1000 A.
AC Current 0.001 to 100 A. 0.1 to 600 A. 0.1 to 1000 A.
DC Voltage 0.1 to 600 V. 0.1 to 600 V. 0.1 to 1000 V.
AC Voltage 0.1 to 600 V. 0.1 to 600 V. 0.1 to 1000 V.
Resistance 10 Ohm to 100 KOhm 1 Ohm to 10 KOhm 10 Ohm to 100 KOhm
Continuity Test
Clamp Size Opening 1/2″ (12.5 mm) Max. 1” (25 mm) Max. 1” (25 mm) Max.
Dimensions 7.95″ (H) x 2.62″ (W) x 1.33″ (D) 7.44” (H) x 2.75” (W) x 1.33” (D) 7.44” (H) x 2.75” (W) x 1.33” (D)
Zero Adjustment One touch button One touch button One touch button
Peak Hold Function 10 mS for DCV and DCA 10 mS for DCV and DCA 10 mS for DCV and DCA.



When should I re-calibrate this clamp-meter?
The CM600 is calibrated before shipping from our factory, but it may need to be re-calibrated from time to time depending on your requirements. If you need to have your CM600 re-calibrated, this procedure can be performed by any properly equipped calibration lab of your preference. Please ask them contact us directly at for calibration instructions.

Is there a line splitter for this clamp-meter?
Unfortunately we do not offer a line splitter at this time, but any standard line splitter should work.

Can I take measurements if the cable doesn’t fit in the clamp?
To measure electrical currents with any accuracy, the clamp has to be completely closed. Clamp meters are calibrated with a closed clamp, otherwise the measurements will vary widely according to the gap, and in some cases it may not be able to measure a current at all.

Does the CM100 have the ability to transduce current to voltage?
The CM100 provides an analog output voltage through the positive and negative socket connectors when set to measure current DCA. This output voltage is proportional to the DC + AC components of the current being measured, and has a ratio of 10 mV/A and a 10 KHz bandwidth limit. Note: All measurement errors for the instrument apply to this voltage output as well.

What are the most common problems with clamp-meter measurement?
The two most common solutions for when you are not getting current clamp meter readings:
1- Make sure that there is a current present in the wire or cable being measured,.
2- When measuring currents, only one conductor should be placed inside the CM100’s jaw. If the current clamp meter jaw is placed on a power extension cable, appliance power cord, etc., the magnetic field from the live wire cancels with the one from the return or ground wire, causing the CM100 to show “0” (please refer to the CM100 User’s Manual)

What can I do if the meter isn’t working right?
If you are having problems with your CM100, (e.g. getting stuck in power up self-test mode) you can try the following procedure to reset the CM100:
1- Open the CM100 and remove both batteries.
2- Wait 10 to 15 min, and then replace the batteries with new ones.
The above procedure will reset the electronic circuit, and likely solve the issue.



  Download Brochure (English)

  Download Manual (English)


Kit Manifest

  • CM100 clamp-meter (core unit)
  • 2 x AAA alkaline batteries
  • User’s manual
  • Test leads
  • Soft carrying pouch


Proposition 65 Warning ⚠

This product can expose you to chemicals including Styrene, which is known to the State of California to cause cancer, and Bisphenol A (BPA), which is known to the State of California to cause birth defects or other reproductive harm. For more information go to: