T&D World Magazine

New Ohmmeter Measures Low Resistance Anywhere

Equally at home in the laboratory, the workshop or in the field, on the bench or on the ground, Megger’s new heavy duty DLRO10HD low resistance ohmmeter combines rugged construction with accuracy and ease of use. It features an internal rechargeable battery and can also operate from a mains supply, even if the battery is completely flat.Features include:

  • High or low output power selection for condition diagnosis
  • Rechargeable battery or line power supply, continuous operation, even with dead battery
  • 10 A for 60 seconds, less time waiting to cool, great for charging inductance
  • High input protection to 600 V, inadvertent connection to line or UPS voltage will not blow a fuse
  • Heavy duty case: IP 65 lid closed, IP54 operational (battery operation only)
  • Rotary switch selects one of five test modes, including auto start on connection, giving ease of use

Like all models in the DLRO10 range, the DLRO10HD, when used with optional terminal insulating test leads, is rated CATIII, 300 V in line with IEC61010.

This versatile new test set is built into a tough but easy-to-carry case that provides an IP65 ingress protection rating when closed and an IP54 rating when the instrument is in use and operating from battery power.

Easy to use with gloved handThe instrument’s rotary switch controls are convenient to operate even with gloved hands, and it incorporates a large backlit liquid crystal display that can be easily read from a considerable distance.

With 0.1 µÙ resolution, 0.2% basic accuracy, and a dedicated mode for use with inductive loads, the DLRO10HD is ideal for applications as diverse as checking the integrity of welded joints and verifying winding resistance in large motors and transformers.

To provide maximum versatility, this innovative test set not only features high compliance but also offers user-selectable high or low power ranges. The high power < 25 W ranges (measuring up to 250 mÙ at 10 A , or 2.5 Ù at 1 A) are ideal for heating a weakness or charging inductive loads. The low power ranges are power limited to 250 mW for applications where it is desirable to avoid heating the item under test. Choice of test modesThe instrument offers a choice of five test modes. In normal mode, the test is initiated by pressing the “test” button. The instrument verifies continuity of all four connections, and then applies the test current in both forward and reverse directions before displaying the result. In automatic mode, the test starts as soon as the probes make contact with the item under test.

Automatic unidirectional mode is the same as automatic mode, but the test current is applied in one direction only. This reduces the testing time, but thermal EMFs from contact between dissimilar metals may reduce the accuracy of the results.

Continuous mode makes repeated measurements at three-second intervals on the same sample. Inductive mode is, as the name suggests, optimised for tests on motors, transformers and other inductive loads, supplying a full 10 Amps for 60 up to seconds.

DLRO10HD heavy-duty low resistance ohmmeters from Megger are supplied, as standard, with a set of test leads fitted with high-quality duplex hand spikes featuring lights to remotely indicate when a test is complete or inadvertent connection to live supply. Test leads with Kelvin clips are also available as an option.
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