Megger DLRO10HD low-resistance ohmmeter

The heavy-duty DLRO10HD low-resistance ohmmeter from Megger 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. When used with optional terminal insulating test leads the DLRO10HD is rated CATIII 600 V, in line with IEC61010.

This 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.

The rotary switch controls are convenient to operate even with gloved hands and a large backlit liquid crystal display can be read from a considerable distance.

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

The test set features high compliance and offers user-selectable high or low power ranges. The high power <25 W ranges (measuring up to 250 mΩ at 10 A, or 2.5 ohm at 1 A) are suitable 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.

The 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, although thermal EMFs from contact between dissimilar metals may reduce the accuracy of the results.

Continuous mode makes repeated measurements at 3 s intervals on the same sample. Inductive mode is optimised for tests on motors, transformers and other inductive loads, supplying a full 10 A for up to 60 s.

The DLRO10HD is supplied with a set of test leads fitted with high-quality duplex hand spikes as standard. These leads feature indicator lights to remotely indicate when a test is complete or if an inadvertent connection has been made to a live supply. Test leads with Kelvin clips are also available as an option.