Fluke 378Fc

Fluke 378 FC Explained: Clamp Ratings, iFlex and What to Check

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Searches for fluke 378fc mean the Fluke 378 FC, a true-rms AC/DC clamp meter with non-contact voltage detection, an iFlex flexible current probe and Fluke Connect wireless logging. Fluke’s product page states CAT III 1000 V and CAT IV 600 V ratings under IEC 61010-2-032 and IEC 61010-2-033, a 999.9 A jaw range and an iFlex range up to 2500 A AC. This guide explains those figures, how to use the clamp within its ratings, and what to check before you buy one.

Quick answer

The 378 FC measures current without breaking the circuit, using its jaw or the included 18-inch iFlex flexible probe.
Fluke states CAT III 1000 V and CAT IV 600 V. Choose the category that matches the circuit, and never use the meter above its rating.
Fluke lists the jaw range at 999.9 A and the iFlex probe at up to 2500 A AC.
Fluke Connect logging and the non-contact voltage function are features Fluke lists. Check that you need them before paying for them.

What a clamp meter does

A clamp meter measures current by sensing the magnetic field around a conductor, so the jaw closes around one conductor instead of breaking the circuit. That is the main reason electricians and technicians use one for live current checks. A clamp meter also reads voltage and resistance on most models. The 378 FC adds a non-contact voltage function, which senses voltage near a conductor without touching it. Non-contact detection is a quick check, not a substitute for a measurement with a rated meter.

The iFlex probe matters when the conductor is too large or too awkward for the jaw. Fluke’s page describes it as a way to measure high current on large conductors. Use it with the same rating discipline as the jaw.

What the Fluke pages state

The table uses only the two Fluke product pages we opened on 2026-10-27. Where a page is silent, the cell says so.

Item	What the Fluke pages state
Measurement ratings	IEC 61010-2-032 and IEC 61010-2-033: CAT III 1000 V and CAT IV 600 V.
General maximum voltage	1000 V between any terminal and earth ground.
Pollution degree	Pollution degree 2, under IEC 61010-1.
Jaw current	999.9 A AC and 999.9 A DC.
iFlex current	Up to 2500 A AC. The included probe is the i2500-18, 18 inches (48 cm).
Leakage clamp	IEC 61557-13, Class 2, 30 A/m or less, for leakage current measurement.
Ingress protection	IP30 with the jaw closed, under IEC 60529.
Voltage detection	Non-contact voltage function, named FieldSense on the product page.
True rms	Named in the product title as true-rms AC/DC.
Data	Fluke Connect software for remote logging, trending and monitoring. Readings can be sent to a smartphone and saved to the cloud.
Publication date	Not shown on the page.

How to use the 378 FC within its ratings

Fluke’s safety guide states that you should pick a meter rated for the highest category you might encounter and a voltage rating that matches or exceeds the work. It also says the rating printed near the input jacks is the one to read, and that a damaged meter or damaged probes should never be used. The 378 FC has two categories on its page, so the category you use depends on where the clamp sits in the installation.

Find the category of the circuit. CAT IV covers the origin of the installation, such as the utility connection and outdoor conductors. CAT III covers fixed distribution equipment such as switchgear and panel feeders. CAT II covers receptacle-connected loads. Use the clamp only where its listed category covers the point you are measuring.
Inspect the clamp and probes. Check the jaw faces, the iFlex probe and the test leads for cracks or damage before each job.
Choose the jaw or the iFlex deliberately. Use the jaw for conductors that fit. Use the iFlex where the jaw cannot close. Keep the iFlex away from energized parts you do not need to measure.
Keep your fingers behind the guard. Hold the clamp by the insulated body and keep the jaw closed on a single conductor. Do not clamp around both the hot and neutral conductors when you want a line current reading, because the fields cancel.
Stop at the rating. Do not use the meter above CAT III 1000 V or CAT IV 600 V. Panel and service work belongs to a licensed electrician.

Things to check before you buy

Category needed. Decide whether your work falls under CAT III or CAT IV. The Fluke rating covers both, but the category decides where you may use it.
iFlex need. The page lists the iFlex probe as included. Confirm that the iFlex is the probe you need for your conductors.
Logging. Fluke Connect logging is a listed feature. Check whether your phone and your workflow need it.
Accuracy and calibration. The pages we opened do not state accuracy figures in the sections we read. Ask the seller for the accuracy table if the measurement tolerance matters for your job.
Leakage work. The leakage clamp rating under IEC 61557-13 is specific to leakage current measurement. Use the function only for that purpose.

Common mistakes with a clamp meter

Clamping both conductors of a cable. A cable with hot and neutral inside the jaw reads the net current, which is often near zero.
Treating non-contact voltage as a measurement. The function is a detector. Confirm voltage with the meter’s voltage ranges.
Ignoring the category of the point you measure. The rating of the meter does not cover a point the category does not reach.
Using the iFlex on a conductor it cannot close around. A loose iFlex reads poorly and can drop onto live parts.

FAQ

What CAT rating does the Fluke 378 FC have?

Fluke’s pages state CAT III 1000 V and CAT IV 600 V under IEC 61010-2-032 and IEC 61010-2-033. Use the category that matches the circuit you are testing.

How much current can it measure?

The jaw is rated to 999.9 A on both AC and DC. The flexible probe reaches 2500 A on AC.

Does it measure true rms?

The product title names true-rms AC/DC. Check the function you need against the product page.

Can I use it on a three-phase panel?

Only where the point you measure falls within the listed category. Panel work belongs to a licensed electrician, and a meter rating does not make an unfamiliar panel safe to open.

Does the 378 FC need a phone to work?

The product pages we opened describe Fluke Connect as software for logging, trending and monitoring measurements. They do not say which measurements need it, so check the meter’s operating instructions before relying on it for a job.

What does IP30 mean on this meter?

The page states IP30 with the jaw closed, under IEC 60529. That is a protection rating against solid objects. It is not a water rating.

How we chose

This explainer covers one model. It does not compare the 378 FC with other clamp meters. The facts come from the two Fluke product pages and the Fluke safety guide we opened on 2026-10-27. The second product page is hosted on a Fluke regional domain, fluke.com.au, and the first on fluke.com. Where a page is silent, the text says so.

What we could not verify

Accuracy figures for the jaw and the iFlex. The sections we read are silent on them.
A publication or revision date for the product specifications. The page shows none.
Battery type and runtime. The pages we opened are silent on both.
Warranty terms. No warranty term appears on the pages we opened.

Bottom line

The Fluke 378 FC is a CAT III 1000 V and CAT IV 600 V rated clamp meter with a large jaw range and an iFlex option. Pick the category that matches your circuit, use the iFlex only where it is needed, and keep panel work with a licensed electrician.

Related guides

Best Fluke clamp meter for automotive work, for a car-focused comparison.
Best multimeters for electricians, for meters used on fixed installations.
Best multimeters for HVAC work, for current and temperature checks on equipment.

Sources

Fluke Corporation, “Fluke 378 FC Non-Contact Voltage True-rms AC/DC Clamp Meter with iFlex,” en-in product page. https://fluke.com/en-in/product/electrical-testing/clamp-meters/378-fc (opened 2026-10-27)
Fluke Corporation, same product, en-us product page. https://fluke.com.au/en-us/product/electrical-testing/clamp-meters/378-fc (opened 2026-10-27)
Fluke Corporation, “Guide to digital multimeter safety.” https://fluke.com/en-us/learn/blog/safety/multimeter-guide (opened 2026-10-27)