Hioki RM3548 Precision Portable Resistance Meter


Product Tags:
Hioki RM3548 Precision Portable Resistance Meter

Precision Portable Resistance Meter

The Resistance Meters RM3544/RM3544-01/RM3548 can measure the winding resistance of devices such as motors and transformers, the contact resistance of power contacts (relays and switches), and the DC resistance of fuses, resistors, and substrates such as conductive rubber and sheets. It does so quickly and at a high level of precision using four-terminal measurement.

The RM3544/RM3544-01 is well suited to use for adjustment and testing on production lines as well as acceptance inspections, while the RM3548 comprises a portable solution for measuring resistance values ranging in magnitude from microohms to megohms, making it ideal for use in production, maintenance, repair and operation of large equipment

High-precision specs in a portable package

  • Expansive range options

Measure from 0.0 µΩ to 3.5000 MΩ
0.1µΩ max. resolution, 0.02% basic accuracy
Max. measurable current of 1A

  • Continuity and resistance measurement in large transformers, motors, and power supply equipment

The RM3548 uses a high current of 1 A to measure lower resistance values more reliably at a resolution of 0.1 μΩ in applications including measuring resistance in large transformers and motors as well as wiring, busbars and connections in power supply equipment

  • Verification of continuity of ground lines in automobiles and fuselage welds and caulking in aircraft

The RM3548 can be used to check ground connections* in  automobiles and fuselage welds and caulking in aircraft using a measurement current of 300 mA (300 mΩ range).

Portable, easy to use, and easy to understand

  • Design is ideal for maintenance and testing/measurement of large products

The included strap can be looped around the neck to support the instrument, leaving the operator’s hands free to hold probes for measurement. The meter uses eight AA alkaline batteries, which provide enough power for approximately 10 hours of testing under normal operating conditions. (Operating times vary with measurement conditions.)

  • Auto-hold and auto-memory functionality

The RM3548 features auto-hold and auto-memory functionality to automatically hold and record data simply by placing the probes in contact with the desired measurement location. This functionality allows measured  values to be recorded automatically as soon as they stabilize without the need for the user to operate any switches.


By installing the LED COMPARATOR ATTACHMENT close to a probe, you can capture judgment results without moving your eyes away from the measurement location and probe.

  • Offset Voltage Compensation(OVC)

Thermal EMF occurs at the contact point of different metals. This voltage affects measurements, and if large enough, can cause measurement errors. The offset voltage compensation function minimizes the effect of thermal EMF to maintain measurement accuracy. Particularly when measuring low resistances where the detection voltage is small, and during low-power resistance measurements, OVC is essential to maintain accuracy.

  • Length conversion function

By setting a resistance value per meter, it is possible to convert resistance values into lengths. This capability is useful when managing cable inventory or estimating PCB pattern lengths.

  • No zero adjustment

Accuracy is defined without any need to perform zero-adjustment. Measurement can be performed as soon as the instrument is turned on.

  • Dramatically improved over voltage resistance

Protection is provided against over voltage input of up to 70 V, preventing damage caused by connecting the instrument to an electrical charge or by the effects of the counter-EMF from inductance. 

  • Acquire measured values recorded in the instrument’s memory over  a USB connection

By connecting the RM3548 to a computer with a USB cable*, you can download measured values stored in the instrument’s memory. *Since the RM3548 provides a mass storage class (read-only) USB interface, there is no need to install special driver software on the computer

Temperature conversion function and interval measurement:Useful in temperature-rise testing

Temperature increase (Δt) is obtained and displayed by converting resistance measurements and ambient temperature.The maximum temperature increase needs to be determined when current is applied especially for verifying motor windings or transformers.The interval measurement function can be used to take measurements at a user-specified interval from the start of measurement. Since measured values can be recorded in the instrument’s memory, the maximum temperature can be easily estimated.

*The temperature conversion function cannot be used simultaneously with the temperature correction function and length conversion function.

1.When a motor or coil has thermally stabilized at room
temperature, measure the resistance (r 0 ) and ambient
temperature (t 0 ) before applying current.
2.Excite the coil, and when the temperature increase appears
to saturate,remove the excitation.
3.After removing excitation, determine the temperature (Δt 1
to Δt n ) from the resistance (rt) measured at each specific
time (t), and the ambient temperature.
4.Project the curve through the collected temperature data (Δt 1
to Δt n ) to estimate the maximum temperature increase (Δt).

Measurement accuracy

  • Resistance measurement accuracy
  • Conditions of guaranteed accuracy
  • Temperature & humidity: 23 °C ±5 °C,  80% rh or less (non-condensing)
  • Guaranteed Accuracy Period: 1 year
  • From 0°C to 18°C and from 28°C to 40°C, add (temperature coefficient ±[1/10 measurement accuracy] / °C).


  • Basic accuracy: 0.02%, Max. resolution: 0.1 μΩ, Max. measurable current: 1 A
  • Measure from 0.0 µΩ (@ 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.
  • High-precision specs in a portable package(high accuracy of 0.02% rdg.)
  • Design is ideal for maintenance and testing/measurement of large equipment.
  • No warmup period or zero adjustment required.
  • Dramatically improved overvoltage resistance (protection up to 70 V DC)
Product Images (click to enlarge)
  • Hioki RM3548 Precision Portable Resistance Meter