10 Amp Micro-Ohmmeters are one the most commonly purchased test instruments and have a multitude of uses which can be divided into Non-Inductive and Inductive applications.
- Busbar joint testing
- Crimp lug testing
- Switch and breaker contact resistance measurement
- Earthing and equipotential bonding
- Welded connections
Inductive testing typically comprises transformer and motor winding resistance measurement which is more demanding. Some instruments can handle it with limitations, others have more capability.
Be Aware of Back EMF!
If the resistance of large transformers or motors is attempted, the windings will remain charged after the test and has to be discharged before the test leads are removed otherwise the Back EMF will give you a nasty shock or damage the instrument.
Be Aware of Remnant Magnetism!
Because micro-ohmmeters test with a DC current it can magnetise the iron core of the device under test. If the core is not demagnetised before connecting the device to the AC mains, a high inrush current can occur tripping the protective devices.
Which Instrument Do I Choose?
Because Micro-Ohmmeters have a multitude of uses, Pacific Test Equipment offers four 10 Amp models from Sonel and AEMC, each offering a choice of price and specifications.
If you need to measure with a resolution of 0.1µΩ then the MMR-640 is recommended. It comes with colour touch screen control and a Li-Ion battery which recharges faster and it can be used on mains power while recharging.
The AEMC 6240 has a resolution of 1µΩ and can handle small inductive loads of up to 0.5H.
If inductive measurements are anticipated, then the options are the Sonel MMR-650 or the AEMC 6255. Both will measure inductive loads with a resolution of 0.1µΩ, will discharge the back EMF and can compensate for temperature.
The Sonel MMR-650 adds demagnetisation making it the preferred choice for transformer and motor testing. Like the MMR-640 the MMR-650 has colour touch screen control, a Li-Ion battery and can be used on mains power while recharging.
All models include 2-year Australian & NZ warranty and are fully serviced and calibrated by Pacific Test Equipment.