Megger® Model DLRO600
Digital Digital Microhmmeter
- Small and weighs less than 33 lbs (14.5kg)
- Test currents from 10 A to 200 A DC
- On board memory for up to 300 test results and notes
- 0.1 μΩ best resolution
- RS232 port to download stored results or for real time output to a printer
- Supplied complete with 16.4 ft (5 m) test leads and download software
- continuously variable output current from 10 A to 600 A, eliminating the need for a variety of instruments at 100 A, 200 A, 250 A, 500 A and 600 A
- on-board memory reducing the possibility of error in recording results
- alphanumeric keyboard
- resolution of 0.1 microhm
The Megger DLRO600 measures resistances between 0.1 µohm and 1µohm, at high currents. This versatile instrument can provide test currents from 10 amps up to 600 amps subject to the load resistance and supply voltage. A large liquid crystal display provides all the information needed to perform a test. All test parameters and measurement results are displayed.
The unique design allows the weight and size of DLRO600 to be kept to a minimum. The instrument weighs less than 33 lbs (15kg). This small size makes DLRO600 equally at home in the workshop, on the production floor or in the field. The high current capability and compact design make DLRO600 suitable for testing circuit breaker contacts, switch contacts, busbar joints or other applications where high current is needed.
300 sets of results may be stored in the on board memory for later download to a PC or may be output directly to a printer via the RS232 port. You may also add notes to any stored result by using the on board alphanumeric keypad, thereby making later identification of results straightforward. As well as adding notes to stored results, the alphanumeric keypad allows you to set the test current directly by typing in the value required. DLRO600 will check the continuity of the test circuit, and will quickly ramp the test current up to the desired level. The keyboard is also used to set upper and lower limits for the result and to prevent the use of excessive currents by setting an upper limit to the allowable test current.
The DLRO600 uses a four terminal measurement technique to cancel the resistance of the test leads from the measurement. DLRO600 operates in one of three modes, which are simply selected from the on screen menu.
CONTINUOUS mode is provided for users who wish to monitor a resistance over a period of time. Connect the test leads, select the test current and press the TEST button. DLRO600 will pass a current continuously, and measure the resulting voltage at 2-second intervals, until the test button is pressed to stop the test or the test circuit is interrupted. In NORMAL mode you connect the leads, select the test current and press the TEST button. The test current will ramp up to the desired level, hold for 2 seconds and then ramp down. The whole process takes approximately 7 seconds.
In AUTO mode select the desired current, and press the TEST button. The TEST lamp will flash to show that the DLRO600 is ready to carry out a test. As soon as the current and potential leads are connected, a test will start. To repeat a test, simply break contact with the voltage probes and remake contact. Measuring individual joints in a busbar is a good example of the convenience to be gained by using AUTO mode. The two current leads are connected to the ends of the busbar. They will remain connected here until all tests have been completed. When the voltage leads make contact across a joint, DLRO600 detects that all four leads are connected, carries out a test and stops. When you move to the next joint DLRO detects the new completed circuit automatically and carries out the next test, and so on until all joints have been tested. The results may be stored automatically and may be recalled to the display or downloaded for review.
Testing of the contact resistance of high voltage alternating current circuit breakers according to IEC62271-100 calls for a test current with any convenient value between 50A and the rated normal current. The similar American standard ANSI C37.09 specifies that the test current should be a minimum of 100A.
Most electrical utilities will prefer to test at higher currents since they believe this is more representative of working conditions. As an extension to this, the high current resistance measurement has been applied to high voltage cables, cable joints, welds, busbars and switchgear in general. Maintenance engineers involved in substation maintenance, both within utilities and end users who take their power at higher voltages, and manufacturers of switchgear, bus bars, distribution panels and circuit breakers will find the DLRO600 a powerful tool.