Fluke 773 Milliamp Process Clamp Meter: Specs and What It Measures

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The Fluke 773 is a milliamp process clamp meter for loop work, not a general-purpose multimeter. It reads current in process loops, sources a loop current for testing, simulates a transmitter, and measures low DC voltage. This guide sets out the figures Fluke publishes for the 773, explains what each function is for, and lists what to check before you use one on a live instrument loop.

Quick answer

The clamp measures mA from 0 to 20.99 mA and from 21.0 to 100.0 mA, according to Fluke’s product page.
Series measurement, mA source and mA simulate each cover 0 to 24.00 mA at 0.2% plus 2 counts.
Voltage source covers 0 to 10.00 V DC, and voltage measure covers 0 to 30.00 V DC.
Fluke lists four AA alkaline cells, an operating range of -10 to 50 degrees C, and a three-year warranty on electronics.

What the 773 measures

A milliamp process clamp measures current in a loop without breaking it. The jaw closes around one conductor, and the meter reads the current in that conductor. That makes it useful on a live 4-20 mA loop where you cannot open the circuit, because opening it would stop the process or the instrument.

Fluke lists two clamp ranges. From 0 to 20.99 mA, the stated accuracy is 0.2% plus 5 counts. From 21.0 to 100.0 mA, accuracy is 1% plus 5 counts. The clamp accepts a conductor up to 4.5 mm (0.177 inch) in diameter. Fluke’s page gives those ranges as the clamp reading, so the clamp is not a substitute for the series or source functions when you need a precise loop check.

The series measurement function reads current through the meter’s test jacks, which means you put the meter into the loop. Fluke lists 0 to 24.00 mA at 0.2% plus 2 counts. Use this when you need the lower-error reading and you can open the loop safely.

Source and simulate functions

The mA source function drives a current through the loop. Fluke lists 0 to 24.00 mA at 0.2% plus 2 counts, with a maximum drive of 24 mA into 1,000 ohms. This is the function you use to check a receiver or a controller input, because the meter supplies the signal.

The mA simulate function replaces a transmitter in the loop. Fluke lists 0 to 24.00 mA at 0.2% plus 2 counts, and a maximum voltage of 50 V DC. A simulate function is useful for checking a display, a valve positioner or a controller without the field device connected. Because simulate draws its current from the loop supply, check the loop voltage before you connect it.

The voltage source function supplies 0 to 10.00 V DC at 0.2% plus 2 counts, with a maximum drive current of 2 mA. The voltage measure function reads 0 to 30.00 V DC at 0.2% plus 2 counts. These two functions are for low-voltage DC signals, not for mains or distribution work.

Published specifications

Clamp mA measurement: 0 to 20.99 mA at 0.2% plus 5 counts; 21.0 to 100.0 mA at 1% plus 5 counts.
Series mA measurement: 0 to 24.00 mA at 0.2% plus 2 counts.
mA source: 0 to 24.00 mA at 0.2% plus 2 counts, maximum drive 24 mA into 1,000 ohms.
mA simulate: 0 to 24.00 mA at 0.2% plus 2 counts, maximum voltage 50 V DC.
Voltage source: 0 to 10.00 V DC at 0.2% plus 2 counts, maximum drive current 2 mA.
Voltage measure: 0 to 30.00 V DC at 0.2% plus 2 counts.
Power: four AA 1.5 V alkaline cells (IEC LR6), listed at 12 hours in mA source into 500 ohms.
Operating temperature: -10 to 50 degrees C. Storage: -25 to 60 degrees C.
Operating humidity: below 90% at under 30 degrees C, below 75% at 30 to 55 degrees C.
Operating altitude: 0 to 2000 m. Ingress rating: IP 40.
Size: 44 x 70 x 246 mm. Weight: 410 g (14.4 oz).
Warranty: three years for electronics, one year for the cable and clamp assembly.

Who uses a 773

The 773 suits instrument technicians and process maintenance staff who check 4-20 mA loops, transmitters, controllers and valve positioners. It is a calibration and fault-finding tool. A general electrician who needs AC current, mains voltage and resistance on building wiring will usually be better served by a clamp multimeter with a mains safety rating.

For a loop check, a typical sequence is to clamp the loop current to see what the transmitter is sending, then use the source function to drive a known current into the receiver and compare the displayed value. If the two readings disagree, the fault is in the receiver or the wiring, not the transmitter. That sequence depends on the loop voltage and wiring being safe to work on, which is why the pre-work checks below matter.

What to check before you use one

Confirm the loop is de-energized or isolated before you open any connection, and confirm the loop supply voltage before you use simulate or source. Fluke’s page gives a 50 V DC maximum on simulate, so do not connect the meter to a loop that could exceed that.

Check the batteries. The page lists four AA cells, and the source function is the heaviest load on them. A weak battery will show up as an unstable source output. Replace the set rather than mixing old and new cells.

Check the clamp jaw and the cable. A clamp that does not close fully, or a cable with cracked insulation, will give a poor reading. Replace the cable or send the meter for service rather than working around the fault.

Keep the operating limits in view. The page lists -10 to 50 degrees C and an IP 40 rating. Do not use the meter in wet conditions or outside its temperature range, and do not expect the stated accuracy outside those limits.

How we chose these figures

Every figure in this guide comes from the Fluke product pages for the 773 listed in the sources below, which show the same specification set on three regional pages. We did not use distributor listings, retailer summaries, third-party manual hosts or forum posts for any specification. Where a figure appeared on all three pages, we kept it; the descriptions of use come from the function names and our reading of those specifications.

What we could not verify

The product pages we opened do not state a safety category such as CAT III or CAT IV for the 773, so this guide does not give one. Fluke’s page does not say whether the 773 is discontinued either, and it lists the unit as available. Check the manual for your unit for the safety category and the full list of operating limits, and check current stock with a seller before you plan a purchase. We did not open an official Fluke PDF manual for the 773 from an allowed source.

Frequently asked questions

Is the Fluke 773 a multimeter?

No. It is a milliamp process clamp meter with source and simulate functions for loop work. It does not measure AC current, mains voltage or resistance.

What is the Fluke 773 clamp range?

Fluke lists 0 to 20.99 mA at 0.2% plus 5 counts, and 21.0 to 100.0 mA at 1% plus 5 counts.

How long does the battery last?

Fluke lists 12 hours in mA source into 500 ohms, using four AA alkaline cells.

For a wider view of clamp meters from the same maker, see our guide to Fluke clamp meters for automotive work and the Fluke multimeter lineup.

Summary

The Fluke 773 is a milliamp process clamp meter with a clamp reading to 100.0 mA, series, source and simulate functions to 24.00 mA, and voltage source and measure functions to 10 V and 30 V DC. Check the specification against your loop, confirm the loop is safe to open, and confirm the safety category in the manual before you use it.

Sources

Fluke, “Fluke 773 Milliamp Process Clamp Meter”, product page (en-sg), https://www.fluke.com/en-sg/product/calibration-tools/ma-loop-calibrators/fluke-773 , opened 2026-10-28.
Fluke, “Fluke 773 Milliamp Process Clamp Meter”, product page (en-in), https://www.fluke.com/en-in/product/calibration-tools/ma-loop-calibrators/fluke-773 , opened 2026-10-28.
Fluke, “Fluke 773 Milliamp Process Clamp Meter”, product page (en-ie), https://fluke.com/en-ie/product/calibration-tools/ma-loop-calibrators/fluke-773 , opened 2026-10-28.