Digital ohmmeters used in electrical safety tests

A manufacturer of insulation monitoring and online earth fault location systems for the healthcare sector is using a Cropico instrument to test the electrical safety of its installations.

Cumbria-based Bender UK, part of the German-owned Bender Group, has equipped its mobile service engineers with DO4002 digital ohmmeters to ensure that earth loops are less than 0.1 ohms when commissioning and servicing electrical equipment.

The lightweight units are very portable, making it easier and quicker for engineers to check the safety of hundreds of Bender isolated power system installations in operating theatres, cath labs, MRI rooms and CT scanners located throughout the UK.

Bender has specified the DO4002 to enable it to comply with Medical Electrical Installation Guidance Notes (MEIGaN), which cover the safety requirements of electrical systems installed in diagnostic imaging, patient treatment and radiotherapy rooms.

This guidance includes buildings, refurbished rooms and transportable diagnostic or treatment rooms and requires the measurement of resistance between each protective earth terminal, socket outlet or every accessible metal part and the earth reference bar in patient medical environments.

In the revised guidance, a minimum test current of 1A is now permitted and the maximum acceptable resistance is 0.1 ohms.

The DO4002 enables users to meet the earthing and equipotential bonding tests required by MEIGaN and has been specifically developed for this type of electromedical installation testing.

A lightweight design and single-push button test operation, with a large direct reading display of measured values, allows ease of use and total portability.

The tester is battery-powered, which means that readings can be taken without the risk of earth-leakage currents from the main power supply interfering with resistance measurements.

In addition, the availability of extended lead lengths of up to 20m means that room sockets are all accessible from a single point, and individual plug tests can be undertaken fast and effectively.

The rugged DO4002 incorporates a number of advanced features to ensure measurement accuracy, including forward and reverse current measurement with auto averaging, true current zero, long scale length and a selectable measurement range from 4mW to 400W, with respective resolutions between 1mW and 100mW.

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