HIOKI RM3548-50 portable precision resistance meter with protective boot and LCD display

RM3548-50 LCD showing 0.1 micro-ohm resolution four-wire resistance measurement

Electrician using HIOKI RM3548-50 to test EV battery busbar connections in automotive workshop

HIOKI RM3548-50 Precision Resistance Meter | Test Equipment

When precision matters on every test, the HIOKI RM3548-50 delivers laboratory-grade accuracy in a handheld package. Measuring from 0.1 µΩ to 3.5 MΩ with 0.02% accuracy, this professional resistance meter handles everything from battery busbar connections to motor winding diagnostics. Four-wire measurement eliminates lead errors, while automatic temperature correction keeps your readings reliable across Australian conditions. UN ECE R100 compliant for hybrid and EV workshops.

Brochure: RESISTANCE METER RM3548-50

Categories: Hioki, Resistance Meter, Test Equipment For Electricians, Test Equipment For Solar PV Tags: Hioki, Micro Ohmmeter, Precision resistance meter Brand: Hioki

HIOKI RM3548-50 Precision Resistance Meter – Micro-Ohm to Mega-Ohm Testing for EV, Motor & Aviation Applications

Why Resistance Testing Accuracy Matters on Job Sites

Every sparkie and maintenance tech knows the frustration: you’re troubleshooting a motor failure, testing battery connections on an EV, or verifying bonding integrity on aircraft components, and your standard multimeter just doesn’t have the resolution or accuracy to give you confidence. When you’re working with micro-ohm measurements – where fractions of resistance indicate the difference between a solid connection and an impending failure – guesswork isn’t good enough.

The HIOKI RM3548-50 Resistance Meter eliminates that uncertainty. Purpose-built for Australian trades working in automotive workshops, aviation maintenance hangars, industrial facilities, and renewable energy installations, this precision instrument brings laboratory-grade measurement capability to portable field work. Whether you’re conducting pre-delivery inspections on electric vehicles, performing scheduled overhauls on aircraft, or diagnosing intermittent faults in three-phase motors, you’ll get repeatable, traceable results that meet compliance requirements.

How the RM3548-50 Solves Real-World Testing Challenges

Unlike basic ohmmeters that struggle with contact resistance and lead compensation, the RM3548-50 uses a four-wire Kelvin measurement method that separates test current from voltage sensing. This means the resistance of your test leads doesn’t influence your reading – critical when you’re measuring connections that should be under 1 mΩ. The offset voltage compensation (OVC) function actively cancels out thermal EMF and residual voltages that can throw off micro-ohm readings, particularly important when working on equipment that’s recently been powered or in hot environments.

What sets this meter apart for Australian applications is the automatic temperature correction function. Copper conductor resistance changes with temperature – about 0.4% per degree Celsius. The RM3548-50 measures ambient temperature simultaneously and compensates readings to a reference temperature, giving you standardized results regardless of whether you’re working in a climate-controlled workshop or out in the field during a 40°C summer day. For motor winding diagnostics, it can even estimate winding temperature from resistance measurements, helping you identify overheating issues before they become catastrophic failures.

Professional Features Built for Trade Applications

EV and Hybrid Vehicle Testing The RM3548-50 meets UN ECE R100 international safety standards, which mandate a minimum 0.2A test current for equipotential bonding verification on electric vehicles. With a maximum test current of 1A, this meter provides definitive pass/fail testing on battery pack connections, motor housing bonds, and high-voltage interlock circuits. The automatic overvoltage protection (up to 60V DC) means if you accidentally probe a live circuit during an EV inspection, the meter shuts down immediately – protecting both instrument and operator. Purpose-designed probes like the L2140 series feature safety-rated alligator clips sized for battery lugs and busbar testing.

Aviation Maintenance Compliance Aircraft maintenance requires documented resistance measurements between structural components to verify lightning strike protection and static discharge paths. The RM3548-50’s specialized L2141 probe features rounded contact points that won’t scratch or damage aircraft skin during bonding tests. The L2142 needle probe can penetrate through paint and anodizing to measure underlying metal-to-metal bonding resistance – essential for corrosion control inspections where you can’t strip coatings. All measurements can be wirelessly transmitted to your tablet using the optional Z3210 Bluetooth adapter, creating instant compliance documentation with timestamps and location data.

Motor and Transformer Diagnostics Three-phase motor winding resistance tests reveal turn-to-turn shorts, phase imbalance, and overheating damage long before insulation breakdown occurs. The RM3548-50’s 0.1 µΩ resolution detects subtle resistance changes between phases that indicate developing faults. For transformer testing, measure primary and secondary winding resistance to calculate copper losses and verify turns ratios. The automatic temperature correction ensures your baseline measurements remain comparable over time, regardless of seasonal temperature swings.

Cable Length Calculation Built-in cable length conversion calculates conductor length from resistance measurements with 1cm precision. Ideal for inventory verification, fault location on installed cables, or confirming supplied cable reels match purchase specifications. Just measure the resistance, input the conductor specification, and the RM3548-50 displays the calculated length – eliminating tedious manual calculations.

Built for Australian Work Environments

The RM3548-50’s rubberized protective boot absorbs workshop impacts and provides a stable base for benchtop use. Eight AA batteries (included) deliver approximately 10 hours continuous operation – enough for a full day’s testing without mains power. The backlit LCD remains clearly readable in direct sunlight, and the memory function stores up to 6000 readings with interval logging as fast as 0.2 seconds for continuous monitoring applications.

Wireless connectivity via the optional Z3210 adapter integrates seamlessly with HIOKI’s mobile app for iOS and Android, or streams data directly into Excel templates on your laptop. Create comprehensive test reports combining resistance readings, site photos, and technician notes without transcription errors or delays.

What Makes HIOKI Meters Different

HIOKI Corporation has manufactured precision electrical test instruments in Japan since 1935, building a reputation for accuracy, reliability, and innovation across industries from automotive to aerospace. The RM3548-50 represents the latest evolution in portable resistance measurement, combining decades of analog circuit expertise with modern digital processing and connectivity.

Each HIOKI meter undergoes individual factory calibration traceable to national standards, with test certificates included. When you purchase through Test Equipment Australia, your RM3548-50 arrives ready for immediate deployment with full manufacturer warranty support and access to our calibration services for ongoing compliance requirements.

TRADE-SPECIFIC APPLICATIONS

For Automotive Electricians & EV Technicians

High-voltage isolation testing on hybrid and electric vehicle battery packs before and after service
Equipotential bonding verification between chassis components per ECE R100 safety requirements
Motor phase winding resistance comparison to diagnose turn-to-turn shorts and phase imbalance
Battery interconnect resistance testing to identify high-resistance joints causing voltage drop and heating
Cable harness resistance measurements for fault location in automotive wiring systems
Charging port contact resistance verification for reliable power delivery

For Industrial Electricians & Maintenance Technicians

Three-phase motor winding diagnostics – detect developing faults before catastrophic failure
Busbar connection testing in switchboards and distribution panels
Earth bonding verification for machinery and equipment to AS/NZS 3000 standards
Transformer winding resistance for copper loss calculations and turns ratio verification
Cable length verification against purchase orders and inventory records
Heater element resistance testing for industrial process heating equipment

For Aviation Maintenance Engineers

Lightning strike protection bonding resistance between aircraft structural components
Static discharge path verification from control surfaces to airframe
Through-paint resistance measurement using needle probes without surface preparation
Avionics equipment bonding for electromagnetic compatibility compliance
Landing gear continuity testing for static dissipation during fueling operations

For Solar Installation & Maintenance Teams

PV array DC cable resistance for system efficiency analysis and fault detection
String conductor joint resistance to identify poor crimps and corrosion
Earthing system verification for lightning protection and equipment safety
Inverter input connection testing before commissioning
Array-to-array equipotential bonding for large commercial and utility-scale installations

For Calibration Laboratories & Test Facilities

Reference standard verification with NIST-traceable accuracy documentation
Field meter calibration checks using precision resistor standards
Quality control testing of manufactured electrical components
Production line resistance testing with data logging and statistical analysis

Specifications

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°C to 99.9°C, accuracy: ±0.5°C (Temperature Sensor Z2002 and RM3548-50 combined accuracy)
Measurement speed	Fixed
Display refresh rate	Without OVC: approx. 100 ms With OVC: approx. 230 ms
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 (RM3548-50 internal memory is recognized as a mass storage device when connected to a PC), wireless communication via Bluetooth® (Z3210 is necessary)
Memory storage	Number of recordable data points: up to 1000 for manual/auto, up to 6000 for interval Interval: 0.2 s to 10.0 s (0.2 s step) Acquisition of data from memory: display, USB mass storage (CSV, TXT files)
Power supply	LR6 alkaline batteries × 8 HR6 nickel-metal hydride batteries × 8 Continuous use: approx. 10 hours (under our company’s conditions) Rated voltage: 5 VA max.
Dimensions and weight	Approx. 199 mm (7.8 in.) W × 132 mm (5.2 in.) H × 60 mm (2.4 in.) D (including the protector) Approx. 890 g (31.4 oz) (including the batteries and protector)
Included accessories	Clip Type Lead L2107 ×1, Temperature Sensor Z2002 ×1, Protector Z5041 ×1, LR6 alkaline battery ×8, Instruction Manual ×1, USB Cable (A to mini-B) ×1, Strap ×1, Spare fuse ×1

FAQ

FREQUENTLY ASKED QUESTIONS (FAQ)

Q: Why does the RM3548-50 cost more than a standard multimeter with resistance function?

Standard multimeters typically use two-wire measurement and lack temperature compensation, making them unsuitable for precision work. The RM3548-50’s four-wire Kelvin method, offset voltage compensation, and 0.02% accuracy specification provide traceable, repeatable measurements required for compliance documentation and warranty work. When testing critical connections on EV battery systems or aircraft bonding – where a bad reading could result in safety incidents or expensive rework – the investment in proper test equipment pays for itself on the first job.

Q: Do I need the optional Z3210 Wireless Adapter, or can I work without it?

The RM3548-50 functions perfectly as a standalone meter without wireless connectivity. The Z3210 adapter becomes valuable when you need to generate professional test reports with minimal admin time, conduct multi-point surveys where manually recording hundreds of readings is impractical, or integrate measurements into existing documentation systems. Many technicians start without it and add the Z3210 when their workflow demands efficient data management.

Q: How often does the RM3548-50 require calibration?

HIOKI recommends annual calibration for maintaining measurement traceability. Test Equipment Australia provides NATA-traceable calibration services for the RM3548-50, returning your meter with certification documenting measurement performance against national standards. For compliance-critical applications like aviation maintenance or AS/NZS 3000 electrical installations, regular calibration ensures your documentation withstands audit scrutiny.

Q: Can the RM3548-50 measure insulation resistance like a megger?

No – the RM3548-50 is specifically designed for low-resistance measurements up to 3.5 MΩ using low test voltages. For insulation testing requiring 250V to 5000V test voltages and measuring into the gigaohm range, you need a dedicated insulation tester such as the HIOKI IR4057 or Megger MIT series. The RM3548-50 excels at conductor resistance, bonding continuity, and motor winding measurements where high voltage would be inappropriate or dangerous.

Q: What’s the difference between the L2140, L2141, and L2142 probe sets?

L2140: Alligator clip probes designed for EV battery terminals and busbar testing – wide jaw opening for large conductors, safety-rated for automotive work
L2141: Rounded-tip probes for aircraft bonding tests that won’t damage anodized or painted surfaces – essential for non-destructive aerospace testing
L2142: Sharp needle probes that penetrate through paint, anodizing, and corrosion to reach bare metal – used when measuring through coatings is necessary

Most Australian workshops start with the included L2107 general-purpose clip leads, then add specialized probes as application requirements develop.

Q: Will the meter work with rechargeable AA batteries?

Yes – the RM3548-50 accepts both standard LR6 alkaline and HR6 nickel-metal hydride (NiMH) rechargeable AA batteries. Using quality rechargeables like Eneloop reduces operating costs and environmental impact while maintaining the advertised 10-hour runtime. The meter’s automatic power save function extends battery life during intermittent use.

Q: How does automatic temperature correction work, and when should I use it?

Copper conductor resistance changes by approximately 0.393% per degree Celsius. When you enable temperature correction and specify your reference temperature (typically 20°C or 25°C), the RM3548-50 measures ambient temperature with the included Z2002 sensor and mathematically corrects the resistance reading to what it would be at the reference temperature. This is critical when establishing baseline measurements for motor windings or when comparing readings taken under different environmental conditions. Without temperature correction, a motor winding might measure 10.5Ω at 15°C and 11.2Ω at 35°C – not because the winding changed, but purely due to temperature’s effect on copper resistivity. Temperature correction standardizes all measurements to a single reference point for valid comparison.