Klein Tools CL390 AC/DC Digital Clamp Meter - Accurate TRMS Testing

In this review the Klein Tools CL390 is presented as a practical, professional clamp meter for electricians and serious DIYers who need reliable, multi-function electrical testing. The bottom line: its auto-ranging TRMS measurements and integrated non-contact voltage tester in the clamp jaw make it a standout tool for capturing accurate AC/DC current and voltage without fuss. Reviewers will find it especially useful when they need true RMS accuracy, a clear reverse-contrast display for dim conditions, and handy features like a test lead holder and included thermocouple.

Key Features

• Auto-Ranging TRMS: Provides accurate readings on complex waveforms so measurements reflect true RMS values for AC and DC signals.
• Integrated NCVT: Built-in non-contact voltage testing in the clamp jaw speeds up live-circuit checks without changing probes.
• Wide Measurement Range: Measures AC/DC current, AC/DC voltage, resistance, continuity, capacitance, frequency, duty cycle and diodes for broad diagnostic capability.
• Temperature Probe Included: Temperature measurements with the supplied thermocouple add an extra diagnostic dimension for HVAC and electrical troubleshooting.
• High-Visibility Display: Reverse-contrast LCD improves visibility in dim environments so readings remain legible on job sites.
• Convenience Features: Test lead holder, data hold, Max/Min and optional magnetic hanger support hands-free and efficient work.

Who It's For

The CL390 is aimed at electricians, field technicians, and competent DIYers who require a portable meter that handles both clamp-based current measurements and standard lead-based tests, with the added benefit of TRMS accuracy for non-sinusoidal loads. It is useful on residential, commercial and light industrial jobs where mixed AC and DC systems are present.

Those who primarily need a screen readable in bright, direct sunlight or who want every niche feature of a lab-grade meter may want to compare other models, since the display is optimized for low-light visibility and customers report it can be hard to read in strong sunlight. Also, if only a basic multimeter is required, the CL390 is more capability than necessary.

Pros & Cons

Pros

• Accurate TRMS readings and auto-ranging simplify complex measurements.
• Integrated non-contact voltage testing in the clamp jaw speeds safety checks.
• Includes thermocouple, test leads with safety caps and a carrying case for job-site readiness.
• High-visibility reverse-contrast display makes readings easier in poor lighting.

Cons

• Display can be difficult to read in bright sunlight, according to some users.
• Auto-power-off may interrupt long diagnostic sessions if not disabled or monitored.

Specifications

Functionality	AC/DC current via clamp, AC/DC voltage, resistance, continuity, frequency, capacitance, diodes, DC microamps, temperature
Current Range	Up to 400 A via clamp
Display	High-visibility reverse-contrast LCD
Measurement Technology	Auto-ranging True Root Mean Squared (TRMS)
Non-Contact Voltage	Integrated NCVT in clamp jaw
Included Accessories	Carrying case, test leads with CAT III/CAT IV safety caps, thermocouple, 3 x AAA batteries, instructions
Convenience	Test lead holder, Max/Min, Rel/Zero, Data Hold, optional magnetic hanger compatibility

Our Verdict

The Klein Tools CL390 is a well-rounded clamp meter that pairs TRMS accuracy with practical job-site features, making it a good value for electricians and serious DIYers who need reliable measurements across many functions. It is especially worthwhile when clampbased current measurement and non-contact voltage detection are common tasks, though users who work exclusively in bright sunlight should check screen visibility for their conditions.

Frequently Asked Questions

Does this meter measure temperature?
Yes. The CL390 includes a thermocouple probe for temperature measurements in electrical and HVAC troubleshooting.

Is non-contact voltage testing built in?
Yes. The NCVT function is integrated into the clamp jaw so you can check for live voltage without changing tools.

What safety accessories are included?
The meter ships with test leads that have CAT III/CAT IV safety caps and comes in a carrying case with instructions and batteries.