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Klein Tools CL390 400A AC/DC Auto-Ranging True RMS Clamp Meter

A 4,000-count True RMS clamp meter that measures AC and DC current to 400 A, voltage to 600 V and DC microamps, with non-contact voltage detection in the jaw and a thermocouple for temperature.

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Klein Tools CL390 400A AC/DC True RMS clamp meter, angled front view
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Photo: Klein Tools

Key facts

AC and DC current
40 A and 400 A ranges; ±(2.0% + 9); minimum measurable 0.3 A; AC 50 to 60 Hz
DC microamps
200 µA range (test leads), ±(1.0% + 5)
DC voltage
400 mV to 600 V; ±(1.0% + 8) on 400 mV, ±(0.8% + 3) on 4 to 400 V, ±(1.0% + 3) on 600 V
AC voltage (True RMS)
400 mV to 600 V, 45 to 400 Hz; ±(1.2% + 5) on 40 V and 400 V, ±(1.5% + 5) on 4 V and 600 V, ±(1.8% + 5) on 400 mV
Resistance
400 Ω to 40 MΩ; ±(1.2% + 3) from 4 kΩ to 4 MΩ
Capacitance
Up to 4,000 µF
Frequency
10 Hz to 60 kHz (8 to 240 V AC RMS)

Which version should you buy?

This page covers: Klein Tools CL390 with standard included accessories.

  • CL390 standard package

    This page

    Model: CL390

    What differs
    Current model with case, test leads, thermocouple and batteries. A magnetic hanger is optional.
    Best for
    AC/DC clamp measurements and temperature checks without extra tools bundled in.
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  • CL380 earlier model

    Model: CL380

    What differs
    Discontinued predecessor that Klein identifies as replaced by the CL390. It is a separate meter, not a CL390 package.
    Best for
    Buyers replacing an existing CL380 who specifically want that older model.

Watch out

  • The standard CL390 already includes the case, leads, thermocouple and batteries.
  • A magnetic hanger is optional; its appearance in a bundle does not mean it comes in the standard box.
  • RT250, RT210, ET310 and line-splitter listings add separate tools or accessories to the same meter.
  • CL380 is the discontinued predecessor; check that the meter label says CL390.

Why people pick it

  • Reads DC current as well as AC, from 0.3 A up to 400 A
  • DC microamp range and a thermocouple make it useful for HVAC work
  • 1.6 in jaw with non-contact voltage detection built in
  • Rated for a 2 m drop; a carrying case is included

Know before you buy

  • Rated CAT III 600V only: not for service-entrance (CAT IV) work
  • Current accuracy is ±(2.0% + 9), and Klein gives 0.3 A as the smallest measurable current
  • 4,000-count display
  • Klein lists no low-impedance (LoZ) mode

Full specifications

AC and DC current40 A and 400 A ranges; ±(2.0% + 9); minimum measurable 0.3 A; AC 50 to 60 Hz
DC microamps200 µA range (test leads), ±(1.0% + 5)
DC voltage400 mV to 600 V; ±(1.0% + 8) on 400 mV, ±(0.8% + 3) on 4 to 400 V, ±(1.0% + 3) on 600 V
AC voltage (True RMS)400 mV to 600 V, 45 to 400 Hz; ±(1.2% + 5) on 40 V and 400 V, ±(1.5% + 5) on 4 V and 600 V, ±(1.8% + 5) on 400 mV
Resistance400 Ω to 40 MΩ; ±(1.2% + 3) from 4 kΩ to 4 MΩ
CapacitanceUp to 4,000 µF
Frequency10 Hz to 60 kHz (8 to 240 V AC RMS)
Temperature-40 to 1832°F (-40 to 1000°C); the included K-type thermocouple is rated below 446°F (230°C) only
Non-contact voltageBuilt into the clamp jaw
Display4,000-count reverse-contrast LCD
Jaw opening1.6 in (4.1 cm)
Other functionsContinuity, diode test, duty cycle, Max/Min, Rel/Zero, data hold; auto power-off after about 5 minutes of inactivity (unless disabled)
Safety ratingCAT III 600V, Class 2, double insulation
Safety standardsIEC/EN 61010-1 and 61010-2-032; conforms to UL 61010-1 and 61010-2-032; certified to CSA C22.2 No. 61010-1 and 61010-2-032
CalibrationAccurate for one year (per the manual)
Drop protection2 m (6.6 ft)
Power3 × AAA
In the boxClamp meter, carrying case, test leads with CAT III/CAT IV safety caps, thermocouple, 3 × AAA batteries, instructions

From manufacturer documentation, checked November 2, 2026. Spotted an error? Tell us.

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