Megger DLRO10HD

The DLRO10HD is a powerful digital low resistance ohmmeter from Megger. The product offers powerful resistance testing technology in a simple and easy to use package which is durable enough for daily use in professional settings where applications can vary.

The DLRO10HD features a heavy-duty outer case, rated to IP65 with the lid closed. This rating means the case will protect the unit from dust and water ingress as well as from any drops or hard hits to the case. With the unit's lid open as it would be during normal operation, the rating is IP54, providing protection from the elements. The unit comes with a 1 year warranty.

Power for the DLRO10HD comes from a rechargeable 6 V, 7Ah NimH battery pack. This battery will take approximately 8 hours to fully charge. In the event that the battery dies on the job during critical testing, the unit can also be powered from line power. The unit also features an auto-off function to conserve battery power.

The DLRO10HD is complies with IEC61010-1, IEC61326-1, and CATIII 300 V safety standards. However, in order to achieve the CATIII 300 V rating, the unit must be used with the optional terminal cover, available from Megger (part no. 1002-390).

Test Modes

The DLRO10HD features five test modes, selectable via a rotary switch on the instrument. Modes include normal, automatic, automatic unidirectional, continuous, and inductive.

To initiate normal mode, simply connect test leads to the unit under test and press the "test" button. The instrument will perform continuity checks on all four connections and apply current in both forward and reverse directions. Results will then appear on-screen. A mode like this one with multidirectional current will be ideal for testing dissimilar metals because it will cancel out the thermocouple effect.

In automatic mode, testing begins as soon as the instrument detects that probes have made contact with a test source. The DLRO10HD will then apply forward and reverse current and display the average value. This mode makes testing more streamlined, especially with the included DH4 handspikes, because there is no need to press "test" every time when testing multiple sources in quick succession.

Automatic unidirectional mode is similar to automatic mode in that testing begins when probes make contact. However, in this mode current is only applied in one direction to make testing faster. Keep in mind that thermal EMF from dissimilar metal bonds can lower the accuracy of this test mode.

In continuous mode, tests are made repeatedly on the same sample as long as leads remain connected. Measurement data is updated every three seconds in this mode until the circuit is broken.

Inductive mode is useful when testing motors or generators, however it requires the user to keep a close eye on voltage stability while the inductive element is charged. When test leads are connected to the test source and the "test" button is pressed, the DLRO10HD sends current through the test sample in one direction. As voltage stabilizes, readings will decrease to the true measurement value. This is where the operator must determine if the result is stable enough.

Applications

The DLRO10HD is capable of measuring low resistance values in multiple areas including railway, aircraft, heavy industry, motors, generators, and more.

The unit can measure any metallic joint, however there can be measurement limitations depending on the application. As an example, imagine a resistance test must be performed on a piece of thin wire. The user must make sure to use a low test current to keep from heating the wire and as a result, changing its resistance.

When taking measurements on motors and generators, the inductive mode on the DLRO10HD must be used. This requires some user knowledge of the induction and charging processes before a correct result can be obtained.

For thicker conductors, bonds, and welds, the DLRO10HD is perfectly suited. Its 10 A range for resistance values up to 250 mΩ makes it an ideal instrument for measuring in these applications.

Keep in mind, electromagnetic noise induced into test leads can sway a reading and result in incorrect test data. The DLRO10HD includes a noise indicator light to alert users to high levels of noise. When the instrument detects noise above its threshold, the unit will prevent tests from being done.