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380940 – 400A True RMS AC/DC Watt Clamp-on

The compact Extech 380940 is a 400 Amp mini True RMS AC/DC power clamp meter with a small diameter jaw designed to reach in small areas while providing power calculations up to 240kW. With the added convenience of instant watt readings, a feature normally reserved for full-size meters, this mini power clamp is useful for essential troubleshooting tasks in plant maintenance, electrical, HVAC, and telecom work, as well as residential electrical repairs, energy audits, fleet maintenance, marine, and motorcycle repair. Complete with test leads, 2 AA batteries, and carrying case.

  • Large LCD with 40 segment analog bargraph
  • Data Hold, Max/Min recall, Auto Zero (DC current), plus low battery indication
  • Auto power off
  • To download the correct user’s manual, please check your product’s serial number (on the back of the unit). A product revision has occurred only if the SN begins with a letter (A, B, etc.)


Specifications Range Resolution Accuracy ±(%rdg+digits) Input Signal Range
AC Power 40kW 10W ±(1.5% + 3d)@50/60Hz 0-250V, 0-400A, PF 0-1
240kW 100W ±(1.5% + 3d)@50/60Hz 0-600V, 0-400A, PF 0-1
DC Power 40kW 10W ±(1.5% + 3d) 0-250V, 0-400A
240kW 100W ±(1.5% + 3d) 0-600V, 0-400A
AC Current 400A 0.1A ±(1.5% + 3d)@50/60Hz Overload protection: 600A AC (AC frequency range 40Hz-1kHz)
DC Current 400A 0.1A ±(1.5% + 3d) Overload protection: 600A DC
AC Voltage 600V 1V ±(1.5% + 2d)@50/60Hz Overload protection: 800V AC
DC Voltage 400V 0.1V ±(1.0% + 2d) Overload protection: 800V DC
Frequency 10kHz 0.01-100Hz ±(0.8% + 2d) Overload protection: 600V AC
Dimensions 7.2 x 2.5 x 1.4″ (183 x 64 x 36mm)
Weight 6.7oz (190g including batteries)
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