Microhmmeter DMOM 600

Accuracy and Reliability

The DMOM-600 is specifically designed for testing EHV circuit-breaker contact resistances, bushing contact joints, welding joints, or for any low-resistance measuring application. This high current and very lightweight (33 lbs/ 15 Kg) micro-ohmmeter is designed to meet the IEEE C57.09-1999 (5.15) requirement for testing circuit breaker contact resistance..

Key features

The DMOM-600 can accurately measure resistance values from 1 micro-ohm to 450 milliohms. A 0.1 micro-ohm resolution is possible with current greater than 10A. The DMOM-600 applies a selectable true DC test current from 10A to 600A to the resistance load to be tested. The DMOM-600 controls the test current’s rise and fall rates. The test current rise and fall rate can be selected from 5 seconds
to 10 seconds. An “Auto Test” mode is also available and can be initiated simply by applying the sense cables’ leads across the two points of interest in the current path. This feature is very convenient when measuring a sequence of several resistance values in a circuit breaker contact. The DMOM-600 can also compare test results against preset limits and determine if a test passed or failed, and a “Pass” or “Fail” flag is displayed accordingly. Since a true DC current (with controlled rise/fall time) is passed through the circuit breaker contact, no magnetic transient is induced into the breaker’s current transformers. This feature greatly reduces the risk of inductively tripping a breaker control (bus differential relay).

With the Dual Ground option, the DMOM-600 can also measure the circuit breaker contact resistance with both sides of the breaker bushing being grounded. When a test current is applied to a circuit breaker with both sides grounded, some of the test current flows through the safety ground cables. Using an external current sensor, the DMOM-600 measures and eliminates this current from the total test current. It then calculates the actual resistance value of the circuit breaker

The DMOM-600 features a back-lit 128 x 64 pixel LCD screen that is viewable in both direct sunlight and low light levels. The resistance readings are displayed in a large font on the LCD screen in micro-ohms or milliohms. The unit is operated via a convenient 44-key “QWERTY” keypad on the front panel. The DMOM-600 can store 128 records of 64 readings internally, and up 999 test records on an external USB Flash drive. Test header information (Company, Substation, circuit breaker ID’s) can also be entered using the 44-key keypad and is stored with each test record. The DMOM-600 also features a built-in 2.5” wide thermal printer that can be used to print test reports in the field.

Windows® based (XP/Vista/7) analysis software is provided with each unit and can be used to remotely control the DMOM-600 via the RS-232C port. Using this software, the user can retrieve test records (from the unit’s memory or a USB Flash drive), analyze test results, and print test results on a desktop printer. Test results can also be exported to PDF, Excel, and XML formats.

The DMOM-600 is furnished with a 15-ft (#1/0 AWG) test cable set. Custom test cable lengths are optionally available. Optional heavy-duty, welding type C-clamps are also available allowing the user to connect the test leads to a wide variety of bushing sizes, bus-bars, or large conductors.

Microhmmeter DMOM-600 Details

Optional clamps

Specifications

Specification	Details
Type	Portable Micro-Ohmmeter
Phisical Specifications	16.8" Wx12.6"Hx12"D (42.7cmx32cmx30.5cm); Weight: 33lbs (15kg)
Input Power	100-240 Vac, 50-60Hz
Resistance Reading Range	1 millioOhm at 600A to 450 millioOhm at 10A
Accuracy	10A to 49.9A: 1%±2uOhms
	50A to 600A: 1%±1uOhms
Test Current Range	10 A to 600A (selectable in 1A steps) Thermally protected DC power supply
Display	Back-lit LCD (128x64 pixels), viewable in direct sunlight and low light levels
Keypad	Rugged, 44-key "QWERTY" membrane keypad
Internal Test Record Storage	128 test records. Each record can contain up to 64 readings
External Test Record Storage	Up to 999 test records on external USB Flash drive.
Computer Interface	RS-232C
Printer	Built-in 2.5" wide thermal printer
PC Software	Windows XP/Vista/7 Analysis Software (included with purchase)
Safety	Designed to meet IEC 61010 (1995), UL 61010-a, and CAS-C22.2 standards
Enviroment	Operating: -10ºC to 50ºC (15ºF to +122ºF); Storage: -30ºC to 70ºC (-22ºF to +158ºF)
Humidity (Max)	90%RH @ 40ºC (104ºF) non-condensing
Altitude (Max)	2000m (6562ft) to full safety specifications
Cables	15ft (4.6m) #1 AWG test cables, power cord, ground cable
Options	Shipping case, 15ft test cables, C-Clamp set, Hand Spike Set, Dual Ground Option
Warranty	One year on parts and labor