High-precision Portable Resistance Meter Measures from µΩ to MΩ

Hioki DC resistance meters measure a broad range of resistance values at a high level of precision. The RM3548 is a high-precision, portable resistance meter capable of measuring resistance levels from microohms to megaohms, and is ideal for the testing and maintenance of large equipment, for example, measuring the winding and weld resistances in large motors and stators for hybrid and electric vehicles.

Product Video

Key Features

  • 0.02 % basic accuracy, 0.1 μΩ max. resolution, 1A max. testing current
  • Measure from 0.0 μΩ (testing current 1 A) to 3.5 MΩ
  • Easily record up to 1,000 data points in memory simply by applying the instrument’s probes
  • Smoothly capture temperature-rise test data using interval measurement
  • Portable design is ideal for maintenance and testing of large equipment

Model No. (Order Code)


Portable resistance tester that’s ideal for low-resistance measurement and testing of large transformers and motors

This resistance tester features a portable design that’s easy to use when performing maintenance work in the field. You can wear the instrument over your neck with the included strap, leaving both hands free to hold the clip-type leads while making measurements. The instrument can be powered by eight AA alkaline batteries for about 10 hours of measurement. (Operating time varies with measurement conditions.)

Reduce the effects of thermoelectromotive force with the offset voltage correction

Thermoelectromotive force refers to the potential difference that occurs at junctions between different metals (see figure). Specifically, the phenomenon occurs where measurement probes and measurement targets come into contact, and at connections between measuring instruments and measurement leads. The magnitude of this thermoelectromotive force varies with the temperature of the measurement environment, increasing as the temperature difference grows. The RM3548 includes an offset voltage correction function that applies the measurement current in both the positive and negative directions and then uses the resulting detected voltages to eliminate the effects of thermoelectromotive force.

Correct resistance values, which vary with temperature, to a reference temperature with the temperature correction function

Temperature correction functions can convert readings to resistance values at a user-specified reference temperature and display the results, even for materials such as copper wire whose resistance varies with temperature. The RM3548’s temperature correction function converts the measured resistance value Rt at the current temperature t to the resistance value Rt0 at the reference temperature t0, as shown in the figure. The Temperature Sensor Z2002 (which comes with the RM3548) is used to perform temperature correction.

Standard-compliant measurement current for EV's equipotential bonding test

The RM3548 stands out as the perfect resistance meter for technicians performing equipotential tests on electric vehicles. This meter complies with the ECE-R-100 and ECE-R136 standards, meeting measurement current requirements of at least 0.2 A. Its measurement current ranges from 500 nA to 1 A, ensuring accurate and reliable readings.

Read more on the equipotential test of an EV

Basic specifications

Accuracy guaranteed: 1 year
Resistance range 3 mΩ (3.5000 mΩ display Max., 0.1 µΩ resolution) to 3 MΩ range (3.5000 MΩ display Max., 100 Ω resolution), 10 steps
Measurement accuracy: ±0.020 % rdg. ±0.007 % f.s.
Testing current [at 3 mΩ range] 1 A DC to [at 3 MΩ range] 500 nA DC
Open-terminal voltage 5.5 V DC max.
Temperature measurement -10.0 to 99.9°C, accuracy: ±0.50°C (Temperature Sensor Z2002 and RM3548 combined accuracy)
Measurement speed Fixed
Display refresh rate Without OVC: approx. 100ms, With OVC: approx. 230ms
Functions Temperature correction, temperature conversion, offset voltage compensation (OVC), comparator (ABS/REF%), length conversion, judgment sound setting, auto hold, auto power save (APS),
Averaging, panel store/panel load, USB communication interface (RM3548 internal memory is recognized as a mass storage device when connected to a PC)
Memory storage Number of recordable data points: (manual/auto) Up to 1,000, (interval) Up to 6,000; Interval: 0.2 to 10.0s (0.2s steps); Acquisition of data from memory: display, USB mass storage (CSV, TXT files)
Power supply LR6 (AA) Alkaline batteries ×8, Continuous use: 10 hours (Under our company’s conditions), Rated power consumption: 5 VA max.
Dimensions and mass 192 mm (7.56 in) W × 121 mm (4.76 in) H × 55 mm (2.17 in) D, 770 g (27.2 oz)
Included accessories Clip type lead L2107 ×1, Temperature sensor Z2002 ×1, LR6 Alkaline battery ×8, Instruction manual ×1, USB Cable(A-to-mini B type) ×1, Strap ×1, Spare fuse ×1

Measurement Leads (11)

*The L2107, Z2002 are bundled with the RM3548

About lead length
A: From junction to probe, B: Probe length, L: Overall length

Note: For L2107, length “A” can be extended by roughly 0.8 m (2.62 ft) by cutting the binding tube. Length “A” for all other leads cannot be extended.

Case (2)