Klein Tools MM325 Digital Multimeter, Manual-Ranging, 600V

The MM325 carries a CAT III 600V safety rating, which covers building distribution wiring, panelboards, feeders and hard-wired equipment, so a 480V three-phase panel is within its rating. It measures up to 600V AC/DC. What it is not rated for is CAT IV work at the service entrance or the utility side of the meter. It is also CE and UKCA certified. Klein's own warnings are worth respecting on that kind of work: verify the meter against a known live voltage before each use, wear appropriate PPE where live conductors are exposed, and don't use it in wet conditions or during electrical storms.

Manual ranging. You select the range on the dial yourself, which means you need a rough idea of what you're measuring before you probe it. Trade-off worth knowing: manual ranging gives you a consistent, steady reading with no hunting between ranges, which is why a lot of electricians prefer it for repetitive work on known circuits. If you're troubleshooting unknown equipment all day and want the meter to sort out the range for you, an auto-ranging meter is the better tool.

Resistance measurement on the MM325 tops out at 2 megohms, which is plenty for continuity on a winding, checking a heating element, or reading a thermistor or resistor in a control circuit. What it will not do is insulation resistance testing. Megging a motor to ground calls for hundreds of volts of test potential and readings well past 2 megohms, and that needs a dedicated insulation tester, not a multimeter. For dead-short and open-winding checks, the MM325 works fine, and it has a dedicated continuity function.

No, and this is the spec that sends most buyers to a different meter. The MM325's current function is 10A DC only, measured in series through the leads. There is no AC current range and no clamp. If you're pulling running amps on a motor, a compressor, or a branch circuit, you want a clamp meter instead. The MM325 is the right tool for AC and DC voltage to 600V, DC current up to 10A, resistance, continuity, diodes and battery testing.

Voltage accuracy is +/- 2%, shown on a 2000 count LCD. At 120V nominal that puts a legitimate reading somewhere in the 117.6 to 122.4V band, which is fine for confirming a circuit is live, verifying a supply is in tolerance, or chasing a voltage drop of any real size. It is a field troubleshooting meter, not a calibration reference, so don't use it to argue over a couple of volts on a service call. The 2000 count display also caps resolution: you get four digits, so a 600V reading resolves to whole volts.

Klein rates the MM325 to withstand a 6.6 foot (2 m) drop. That is above typical ladder-platform height for most residential and light commercial work, so a fall from the second or third step onto a hard floor is within what the meter is built to take. The housing is ABS. It weighs 8.8 oz (250 g), so it isn't a brick in a pouch either.

Test leads, batteries and the user manual are all included, so the MM325 works out of the box. It runs on 2 x AAA cells, which is the size to keep in the van for replacements. Battery and fuse compartments are accessible from the outside of the case, so swapping a blown current fuse or dead cells doesn't mean tearing the meter down. There is a low battery indicator on the display to warn you before readings start drifting.

Lead Alert is an LED warning that tells you your test leads are in the wrong jacks for the function you've selected on the dial. The classic way to destroy a meter, or blow the fuse and pop an arc, is leaving a lead in the 10A current jack and then probing a live 240V circuit. The LEDs flag that before you touch the probes to anything. On a manual-ranging meter where you're moving the dial constantly, that is a genuinely useful piece of protection for an apprentice or for anyone working fast.

Klein specifies the MM325 for basic and controlled electromagnetic environments, meaning residential, business and light-industrial locations. For property maintenance, apartment turns, office fit-outs, small commercial service work and general MRO troubleshooting that's the right envelope. Heavy industrial floors with large VFDs, welders or big switchgear generate electromagnetic conditions outside what this meter is specified for, and that kind of environment also usually wants True RMS and AC current capability that the MM325 doesn't have.

The meter body measures 6.41 in (16.2 cm) long, 3.13 in (7.9 cm) wide and 1.83 in (4.6 cm) high, at 8.8 oz (250 g). That is a standard handheld meter footprint and it drops into a typical electrician's pouch meter slot or a bag pocket without a fight. The orange and black housing makes it easy to spot on a dim job site or in a crowded gang box tray.

There's a backlit LCD for exactly that. The other feature that matters in an awkward spot is Data Hold: probe the terminals with one hand while you're braced in a panel or under a floor, freeze the reading, then pull your head out and read it. Auto Power-Off is also on board so the meter doesn't drain its AAAs if you set it down mid-job.

Both are built-in functions. The battery test setting loads the cell and reads it under load, which is the only way to catch a battery that shows full open-circuit voltage and collapses the moment it's asked to do work, the usual culprit behind a dead smoke detector or a thermostat that drops out. Diode test checks for forward voltage one way and a block the other, so you can find a shorted or open diode on a control board or in a rectifier without pulling it. Continuity testing rounds out the set for ringing out conductors and checking fuses and switches.

Klein Tools MM325 is both the model and the manufacturer part number, so MM325 is what goes on the PO. Klein numbers its handheld meters in the MM series, and the digits separate them, so an order needs the full MM325 rather than just "Klein multimeter" if you want manual ranging with a 600V CAT III rating and 10A DC current.