Megger Test Equipment: Microhmmeters

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Megger has been setting industry standards for all low resistance measuring instruments for a while now. The fully automatic DLRO models 10 and 10X are adept at selecting the best suited test currents. With test currents going up to 10 A D.C, the DLRO instruments are perfect for measuring resistances in the 0.1 µΩ- 2000Ω range. The DLRO 10X model gives the user greater levels of control over the entire measurement process. The menu system with a twin-axis paddle allows the user to physically select the maximum allowed test current.This is an advanced level of control for anyelectrical test equipment.

Megger makes both these instruments light and portable for convenient use in both laboratory and field conditions. Equipped with modern LED and LCD displays, they are capable of cancelling out any standing voltage effects across individual test samples. The DLRO 10X is capable of storing recent test results along with any notes relevant to a given test. The instruments are equipped with duplex hand spikes that come with long leads. One probe is fitted with an LED indicator similar to the display that checks whether all the four probes have made contact.

Megger test equipment is typically powered by interchangeable nickel metal hydride battery packs. The exhausted battery can be easily recharged using a simple external charger. The battery pack comes with a stand-alone indicator which indicates the battery status in spite of being disconnected from the instrument. Fitted with the RS232 communications, the DLRO 10X allows for download, storage, and retrieval of results in real time. The DLRO 10X is capable of storing almost 700 sets of different results. These results may also be copied onto a PC.

The DLRO instruments 10 and 10X find varied applications to suit the needs of individual users. Accurate measurements of low resistance may range through inspection of components of received goods to welded joints and ground bonding. The typical applications include making simple D.C resistance measurements in the following:

  •        Busbar and cable joints
  •        Contact breakers and switch resistance
  •        Welded joint integrity
  •        Static control circuits and aircraft frame bonds
  •        Quality control in resistive components
  •        Inter-cell connections of battery systems
  •        Motor winding and transformer resistance
  •        Pipe and rail bonds
  •        Welds, fuse and metal alloy resistance
  •        Cable and wire resistance
  •        Composites such as graphite electrodes
  •        Lightning conductor and transmitter aerial bonding

Measurement modes available for the Megger meter
Both the DLRO instruments- 10 and 10X, work on varied measurement modes. The DLRO 10 displays the average of measurement achieved while the DLRO 10X is capable of displaying both average and individual measurements.

In normal mode, tests can be initiated by pressing a test button present on the front panel. All four connections are maintained in continuity and then the reverse and forward currents are applied.

In auto mode, reverse and forward current measurements are made and the average is put on display by simply making contact with the four probes. Every time you attach the set of probes, a test is done without necessitating any button pushes.

In continuous mode, repeated measurements may be made onto the same sample. Just connect the leads and push ‘test’ and the measurement is automatically updated once every 3 seconds till such a time as the circuit is broken.

In inductive mode, the instruments are employed in measuring inductive loads. Measuring inductive loads require you to wait until the voltage is stabilized. Once the test leads re properly connected and a test current is started, the instrument needs to wait a few seconds for the voltage to get stabilized. Measurement here is made only with forward current.

Unidirectional mode is present only in DLRO 10X. The current is applied along a single direction. Although this speeds up the overall measurement process, standing emfs present in the circuit cannot be negated. The testing process begins automatically right after the probes are connected.