Skip to content
AkerminMeasure. Monitor. Improve. Compare Products
Review

Fluke 377 FC Review: Non-Contact Voltage and Current Measurement

The Fluke 377 FC changes the basic workflow of a clamp meter: with FieldSense, the jaw reads both voltage and current from an insulated conductor at once. This review explains how that works, what it needs to work, and how the 377 FC differs from the 378 FC.

By the Akermin Editorial Team · 4 min read

As an Amazon Associate, Akermin earns from qualifying purchases. Product links on this page are affiliate links.

Fluke 377 FC Review: Non-Contact Voltage and Current Measurement

Fluke · Fluke 377FC AC/DC TRMS Non-Contact Voltage Wireless Clamp w/iFlex

View on Amazon

Price and availability are shown on Amazon and can change at any time.

Verdict

The Fluke 377 FC is a 1000 V, 1000 A True RMS AC/DC clamp meter whose defining feature is FieldSense: clamp the jaw around an insulated conductor, clip one lead to ground, and the display shows voltage and current together without a probe ever touching a live wire. On a three-phase panel that turns a sequence of lead placements into three clamp operations. It includes the iFlex flexible probe for large conductors and Fluke Connect for wireless logging. Its sibling, the 378 FC, adds a power quality indicator and power readings; if you never need those, the 377 FC is the lower-cost way to get FieldSense. For electricians who spend their day in live panels, the documentation supports it as a productivity and safety tool rather than a novelty.

Who It Is For

  • Commercial and industrial electricians who take many voltage and current readings in live panels.
  • Maintenance teams that log readings to a phone for records.
  • Anyone who wants to reduce lead contact with energised conductors.

For how FieldSense fits alongside conventional meters, see choosing a clamp meter.

Documented Specifications

Item Documentation
Non-contact measurement FieldSense voltage and current through the jaw
Measurement type True RMS AC and DC
Current through jaw AC and DC to 1000 A (manufacturer)
Voltage AC and DC to 1000 V (manufacturer)
Flexible probe iFlex included, extends AC current to 2500 A (manufacturer)
Three-phase Voltage and current tests with fewer steps
Connectivity Fluke Connect software for logging, saving and sharing

The safety category rating and accuracy figures are on the manufacturer’s datasheet; check the current revision before relying on a specific tolerance.

How FieldSense Works

A conventional clamp reads current from the magnetic field around a conductor. FieldSense adds sensing of the electric field, which is proportional to the conductor’s voltage relative to a reference. The reference is provided by a single test lead clipped to ground. From the two fields the meter computes voltage and current and, because both are measured at the same instant, it can show them side by side. The practical constraints are that the conductor must be insulated and separated from its neighbours in the jaw, and the ground reference must be a genuine ground. FieldSense is an AC voltage function; DC voltage still uses the leads in the conventional way. Owners describe the biggest gain on three-phase equipment, where each phase is clamped once for both values.

iFlex and Fluke Connect

The included iFlex is a flexible Rogowski-type probe that wraps around busbars, bundled cables and conductors that will not fit a rigid jaw. It extends AC current measurement well beyond the jaw limit and reaches into places a clamp cannot. Fluke Connect sends readings to the phone over Bluetooth, which has two uses: reading a meter left clamped inside an enclosure from outside the arc-flash boundary, and logging a value over time to catch intermittent problems. Reports can be shared from the app. The app requires an account and the logging is limited by phone range.

Build and Everyday Use

The 37x FC series shares a robust body with a large backlit display and a jaw sized for feeders. It is heavier than a compact 400 A clamp and is not the meter for a residential service call in a cramped closet. The auto-ranging display and the simultaneous readout reduce selector changes. The meter runs on AA batteries and owners report reasonable life with Bluetooth in use sparingly. For the current measurement technique that applies to any clamp, see measuring current with a clamp meter.

Strengths

  • Voltage and current from one clamp operation without touching a live conductor.
  • True RMS AC and DC current with a high jaw limit and iFlex included.
  • Three-phase surveys in a fraction of the usual steps.
  • Wireless logging and reporting through Fluke Connect.

Limitations

  • FieldSense still needs a ground reference lead and an insulated, separated conductor.
  • No power quality indicator or power readings; those are on the 378 FC.
  • Larger and higher priced than a general-purpose 400 A clamp.

How It Compares

The Fluke 378 FC is the same meter with a power quality indicator and power measurement. The Fluke 374 FC offers Fluke Connect and a 600 A jaw without FieldSense at a lower price. The Fluke 381 takes a different approach to distance with a detachable display. For solar strings above 1000 V, the Fluke 393 FC is the purpose-built model.

How We Research

This review is based on the manufacturer’s published specifications, the Amazon product listing and owner reports. We did not run laboratory tests. Related: measuring AC voltage safely.

Fluke 378FC AC/DC TRMS Non-Contact Voltage Wireless Clamp w/PQ Indicator & iFlex

Fluke 378FC AC/DC TRMS Non-Contact Voltage Wireless Clamp w/PQ Indicator

View on Amazon
FLUKE-374 FC 600A Ac/Dc TRMS Wireless Clamp

FLUKE-374 FC 600A Ac/Dc TRMS Wireless Clamp

View on Amazon
Fluke 381 Remote Display True-RMS AC/DC Clamp Meter with iFlex

Fluke 381 Remote Display True-RMS AC/DC Clamp Meter with iFlex

View on Amazon

Products shown because their documented specifications fit this guide. Price and availability are on Amazon and can change.

Frequently Asked Questions

How does FieldSense measure voltage without test leads?

The jaw senses the electric field around an insulated conductor and, with a single lead providing a ground reference, calculates the voltage. Current is read magnetically as with any clamp. Both appear on the display at the same time.

Does it still need a ground lead?

Yes. FieldSense needs a reference to ground, made with the supplied lead clipped to a grounded point. What it removes is contact with the live conductor.

What is the difference between the 377 FC and 378 FC?

The 378 FC adds a power quality indicator and, per the manufacturer, power and power factor readings that use the simultaneous voltage and current measurement. The 377 FC gives voltage and current without those derived values.

What is Fluke Connect?

A phone app that receives readings from the meter over Bluetooth so you can view them at a distance, log them over time, and share reports.

Affiliate disclosure: Akermin earns a commission from qualifying Amazon purchases made through links on this page. Our editorial picks are based on documented specifications and owner feedback, not commissions.