Fluke 323 Clamp Meter: Published Specs, CAT III 600 V Rating and What to Check
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The Fluke 323 is a true-RMS clamp meter for electricians who need current readings without breaking the circuit. It clamps around a single conductor, reads AC current up to 400 A, and also measures AC and DC voltage, resistance and continuity. Buyers usually want two answers before they commit: how accurate the current reading is, and which safety category the meter carries. This guide uses the figures Fluke publishes for the 323 and explains the ratings in plain terms.
Quick answer
The Fluke 323 is a true-RMS clamp meter with a 400 A AC current range, published AC current accuracy of 2% ±5 digits from 45 Hz to 65 Hz and 2.5% ±5 digits from 65 Hz to 400 Hz, AC voltage accuracy of 1.5% ±5 digits and DC voltage accuracy of 1.0% ±5 digits. Fluke rates it CAT III 600 V and CAT IV 300 V, and lists a maximum conductor size of 30 mm. It is a clamp meter for distribution-level current checks, not a service-entrance tool for CAT IV work at high voltage.
How we chose these specs
Every figure in this article comes from Fluke’s own product pages for the 323, read on the US and Australian Fluke sites, plus Fluke’s safety guide for the explanation of CAT categories. We did not use retailer listings, forum posts or search-result snippets for any value. Where the two product pages agree, we report the value once.
Published specifications
| Function | Published range | Published accuracy |
|---|---|---|
| AC current | 400.0 A | 2% ±5 digits (45 Hz to 65 Hz); 2.5% ±5 digits (65 Hz to 400 Hz) |
| AC voltage | 600.0 V | 1.5% ±5 digits |
| DC voltage | 600.0 V | 1.0% ±5 digits |
| Resistance | 400.0 Ω and 4000 Ω ranges | 1.0% ±5 digits |
| Continuity | up to 70 Ω | Listed as ≤ 70 Ω |
The 323 measures AC current as true-RMS. Fluke lists a maximum wire diameter of 30 mm, which it gives as 600 MCM. The meter body measures 207 × 75 × 34 mm. Fluke publishes a two-year warranty for the 323.
What the CAT III 600 V and CAT IV 300 V ratings mean
Fluke lists the 323 as CAT III 600 V and CAT IV 300 V. The two ratings describe different environments and different voltage limits. CAT III covers three-phase distribution, including switchgear, feeders and branch circuits in buildings, at voltages up to 600 V. CAT IV covers the service entrance and outdoor conductors, but the 323 is rated for that environment only up to 300 V.
Fluke’s safety guide makes the same point in general terms: choose a meter rated for the highest category you might reach, and match the voltage rating to the system you are measuring. A CAT III 600 V clamp is a good match for panels and distribution equipment in buildings. It is not the right tool for measuring at a utility connection or outdoor service conductors above 300 V.
Where the 323 fits
The 323 suits electricians who check load current on feeders, branch circuits and motor supply cables. Clamping is faster than breaking the circuit, and the 400 A range covers most building-scale loads. The 2% accuracy on AC current from 45 Hz to 65 Hz is adequate for load balancing and general troubleshooting. The voltage and resistance functions let you check supply voltage and continuity with the same meter, so you carry one tool instead of two.
For measurements beyond these ranges, the 323 is not the right choice. It does not offer DC current, and it is not a substitute for a meter built for higher current or higher-category work. Hobbyists who only need to check a small appliance can use a simpler clamp at lower cost.
Using a clamp meter safely
A clamp meter is read differently from a multimeter. Before you clamp a conductor, make sure the jaws close fully and that only one conductor sits inside them. Two conductors carrying opposite currents cancel each other out, and the reading will be wrong. Keep your hands behind the finger guards on the jaws, and do not clamp a conductor whose insulation is cracked or whose ratings you have not checked.
Before current work, check the circuit’s voltage with the meter so you know whether the supply is live. When you measure voltage with the 323, use the voltage input jacks and keep the leads in good condition. If you are unsure of a circuit’s category or voltage, stop and check the rating before you go further.
Reading the specifications with real jobs in mind
The 323’s accuracy figures are percentages with a fixed number of digits added. On a large load near the top of the 400 A range, the percentage term controls most of the uncertainty. On a small current, the digits term is a bigger share of the error. For load balancing, where you compare readings across phases, a 2% to 2.5% band is usually enough to spot an imbalance. For calibration of other instruments, it is not, and you need a meter with a tighter published figure.
The 323 reads AC current as true-RMS, so distorted waveforms from variable-speed drives and electronic loads are measured more reliably than with an average-responding clamp. The published figures apply within the stated frequency bands, 45 Hz to 65 Hz and 65 Hz to 400 Hz. Readings outside those bands should be treated as indicative only.
Clamp readings also depend on position. Center the conductor in the jaws and keep the jaws fully closed. A loose or off-center clamp can give a reading that differs from the true current, so reposition the meter and read again if the value looks unexpected.
Buying checklist
- Match the CAT rating to the highest category you will work in. The 323 covers CAT III 600 V and CAT IV 300 V.
- Check that the largest conductor you need to clamp fits the 30 mm capacity.
- Decide whether you need DC current. The 323 does not offer DC current, so pick another clamp if you need it.
- Choose a meter that matches the accuracy you need. The 2% and 2.5% figures are sufficient for most load checks but may not suit calibration work.
- Keep the meter in a case. Clamp jaws and display glass are easy to damage in a tool bag.
Where to buy
If the 323 matches your work, you can check its current listing on Amazon. The link below is an affiliate link and does not change the specifications covered in this article.
Related guides
For a broader comparison of clamp meters, read our guide to the best AC clamp meter. If you are choosing a clamp for HVAC work, see our guide to the best clamp meter for HVAC.
What we could not verify
The Fluke 323 user manual and data sheet links on the product pages returned errors or unreadable files in our session, so this article relies on the product page text. We did not find a published jaw dimension apart from the 30 mm maximum conductor size. The 323 product page does not state a separate frequency range beyond the 45 Hz to 400 Hz accuracy bands, so we have not quoted one. The page also does not give a crest factor or a bandwidth figure.
Frequently asked questions
What is the maximum current the Fluke 323 measures?
Its AC current range is 400.0 A, according to Fluke’s product page.
Is the Fluke 323 rated for CAT IV work?
Only up to 300 V. Fluke lists CAT IV 300 V, and CAT III 600 V for distribution work.
Does the 323 measure DC current?
Not according to the product page, which lists DC voltage and resistance but no DC current function.
Sources
- Fluke, “Fluke 323 True RMS Clamp Meter”, https://www.fluke.com/en-us/product/electrical-testing/clamp-meters/fluke-323 (opened 2026-10-28).
- Fluke Australia, “Fluke 323 True RMS Clamp Meter”, https://fluke.com.au/en-us/product/electrical-testing/clamp-meters/fluke-323 (opened 2026-10-28).
- Fluke, “Guide to digital multimeter safety”, https://fluke.com/en-us/learn/blog/safety/multimeter-guide (opened 2026-10-28).
