Whether you're testing grounding connections, verifying circuit continuity, or performing precision lab measurements, choosing the right ohmmeter is critical for accuracy, efficiency, and safety. With so many types available—milli-ohmmeters, micro-ohmmeters, insulation testers—it helps to understand which features matter most for your application.
1. Define Your Measurement Needs
Start by identifying the type of resistance you're measuring:
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Low resistance (below 1 Ω): Ideal for grounding systems, bonding connections, switchgear, and busbars. Use a micro-ohmmeter.
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Very low resistance (below 1 mΩ): For applications like transformer windings or contact resistance, look for a model offering Kelvin (4-wire) measurement and test currents of 10 A or more.
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Medium to high resistance (over 1 Ω to GΩ): Insulation resistance testers are more suitable here, especially for safety compliance checks on cables and motors.
2. Match the Test Current to Your Application
The higher the test current, the more stable and accurate the reading, especially for very low resistances.
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100 mA to 1 A: For general low-resistance tests (e.g., in manufacturing or QA)
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10 A: For switchgear, connectors, and power systems
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100 A or more: For substations, rail applications, and heavy-duty testing
3. Portability vs. Bench-Top Precision
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Portable ohmmeters are battery-powered, rugged, and ideal for field technicians.
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Bench-top models offer superior stability, higher resolution, and data logging for lab or production environments.
4. Accuracy and Resolution
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Look for instruments with resolution in the micro-ohm (µΩ) range if you're testing very low resistances.
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Consider accuracy specs and repeatability—especially important for high-stakes environments like utilities or aerospace.
5. Data Logging and Communication
If you're working in QA or need to document results:
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Choose a model with internal memory or USB/RS-232 output for exporting data.
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Software compatibility can help streamline reporting.
6. Calibration and Support
Buy from a supplier who can service and calibrate your instrument. Regular calibration is essential to maintain compliance and measurement integrity.
Why Choose Duncan Instruments?
Since 1968, Duncan Instruments has specialized in ohmmeters—from handheld milli-ohmmeters to high-current micro-ohmmeters. We don’t just sell them—we calibrate and service hundreds each year from our Ontario facility. Need help selecting the right model? Contact us for expert advice.
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