Hioki RM3548-50 Handheld Precision Resistance Meter

A handheld four-wire resistance meter from 0.1 microohm to 3.5 megohm

The Hioki RM3548-50 is a precision handheld resistance meter that measures from 0.1 micro-ohm up to 3.5 megohm. It uses the DC four-terminal method with offset voltage compensation (OVC), which removes the effect of thermoelectric voltages at the contacts, and its 3 milliohm range uses a 1 A test current for a resolution of 0.1 micro-ohm. Hioki positions it for EV maintenance, aircraft overhaul and motor inspections, and it also suits large transformers, wiring and busbars.

Beyond reading resistance, the meter converts values with temperature correction (for copper wire and similar materials), estimates motor and transformer winding temperature rise from the change in resistance, and calculates cable length from a resistance per metre value with 1 cm resolution. An interval measurement function records data at 0.2 s to 10 s intervals for estimating temperature rise. A PASS/FAIL comparator and a red backlight that warns if the probes touch a live battery are included.

Safety is built in: the circuit is protected up to 42.4 V peak AC or 60 V DC, and the meter stops measuring and alerts when an incorrect voltage input is detected. Hioki states that the RM3548-50 meets the UN ECE R100 requirement for a minimum measurement current of 0.2 A, which matters for equipotential bonding checks on electric vehicles. Data go to Excel through the HID function and to a mobile app, both requiring the optional Wireless Adapter Z3210.

Technical specifications

Probes and applications

The supplied accessories are the clip type lead L2107, temperature sensor Z2002, protector Z5041, eight LR6 batteries, a USB cable, strap, spare fuse and the manual. A range of optional probes is listed: pin-type leads L2140, 9465-10 and 9465-11, the L2141 lead with rounded tip for firm probing without damaging a surface, the L2142 with a sharp edge that measures through paint or coating, a large clip lead 9467, pin lead 9772, tip pins and a zero-adjustment board, plus a carrying case C1015.

For EV and hybrid maintenance the brochure recommends L2140 and 9465-11; for aircraft bonding checks L2141 and L2142; for motors, transformers and cables the bundled L2107 or the 9467. Hioki lists equipotential bonding tests, battery connection checks, motor winding inspections, busbar joints, wire and cable resistance and, as a 4-wire instrument, contact resistance of connections as typical uses.

What to confirm before ordering

State the lowest resistance you need to measure and the probe geometry for the job, since probe selection decides whether the contact can be made without damaging paint or coatings. Confirm if wireless transfer (Z3210), a carrying case, extra leads or a calibration certificate are needed. The brochure is dated April 2026 and contents can change without notice, so check the revision when ordering.

Related Hioki products: Hioki FT6380-50 Clamp-On Earth Resistance Tester, Hioki IR5050 5 kV High Voltage Insulation Resistance Tester, Hioki FT6031-50 IP67 Earth Ground Resistance Tester, Hioki CM4375-50 1000 A AC/DC True RMS Clamp Meter, Hioki CM4141-50 2000 A AC True RMS Clamp Meter, Slim Jaw and Hioki IR4056-20 Digital Insulation Tester, 5 Voltage Ranges.

Documents and quotation

The attached Hioki document is the RM3548-50 brochure in English. For higher test currents see the Megger DLRO10X 10 A digital low resistance ohmmeter or the Metrel MI 3242 MicroOhm 2A; more instruments are in the portable test and measurement category. Send the order code, probes and quantity for a quotation from Seven Star LLC.