Microhmmeter DMOM 200 S3

High current and very lightweight

• The DMOM-200 can accurately measure resistance values from 1 microohm to 5 ohms
• Very lightweight: 19.8 lbs. (8.9 Kg)
• The DMOM-200 applies a selectable true DC test current from 1A to200A to the resistance load to be tested.
• Stores test records on-board or on external USB Flash drive

The DMOM-200 is Amperis’ fourth generation, microprocessor-based, true DC micro-ohmmeter. It is 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 (16.8 lbs/ 7.6 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 200 can accurately measure resistance values from 1 microohm to 5 ohms. A 0.1 micro-ohm resolution is possible with current greater than 5A. The Auto-Ohm-200 S3 applies a selectable true DC test current from 1A to200A to the resistance load to be tested. The Auto-Ohm-200 S3 controls the test current’s rise and fall rates. The test current rise and fall rate can be selected from5 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-200 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 200 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-200 measures and eliminates this current from the total test current. The Auto-Ohm then calculates the actual resistance value of the circuit breaker.

The DMOM-200 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 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-200 can store 128 records of 64 readings internally, and up to 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-200 S3 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-200 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 records can also be exported to PDF, Excel, and XML formats.

The DMOM-200 is furnished with a 30-ft test cable set. A 15-ft test cable set is also available as an option. Test cables are terminated with heavy duty welding type clamps. The test current and voltage sense cables are isolated and fastened to the clamp jaws. This feature allows for a simple connection to the circuit breaker bushing. An optional voltage sense cable and probe can be used to measure resistance in small access locations. 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 200 S3 details

1. Ground conection
2. Dual Ground conection
3. Built-in circuit breaker
4. RS-232C Interface.
5. USB Flash Drive Interface.
6. Voltage Lead Connector.
7. LCD Display.
8. 44-key “QWERTY” keypad.
9. Current Lead Connector.
10. Printer

Typical DMOM 200-S3 dual ground Connection

Specifications

Specification	Details
Type	Portable Micro-Ohmmeter
Physical Specifications	18" Wx7"Hx15"D (45.7cmx17.8cmx38.1cm); Weight: 19.8lbs (8.9kg)
Input Power	100-240 Vac, 50-60Hz
Resistance Reading Range	100mOhms a 200A y 5Ohms a 1A
Accuracy	1A to 4.99A: 1%±10uOhms
	5A to 9.99A: 1%±2uOhms
	10A to 200A: 1%±1uOhms
Test Current Range	1 A to 200A (selectable in 1A steps). Thermally protected DC power supply
Display	Back-lit LCD (128x64 pixels), viewable in direct sunlight and low light level
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 (6562 ft) to full safety specifications
Cables	30ft (9.1m), #1 AWG test cables, power cord, ground cable
Options	Shipping case, 15ft test cables, C-Clamp set, Hand Spike Set, Dual Ground Option
Warrantly	One year on parts and labor