DLRO100 series of digital low resistance micro-ohmmeters
Perform high current low resistance testing in almost any location, even if there is no access to a mains supply
Perform high current low resistance testing in almost any location, even if there is no access to a mains supply
Key Benefits
- Small, lightweight, and portable
- Advanced design for safe operation
- High noise immunity
- Smooth DC output for circuit breaker testing
Description
The DLRO100 series of digital low resistance micro-ohmmeters are portable, lightweight instruments that can deliver a test current of 100 A. They can be supplied with internal rechargeable Li-ion batteries that provide sufficient power for up to 200 manual/automatic tests on a single charge. This degree of autonomy makes it easy for you to perform high current low resistance testing in almost any location, including areas without access to a mains power supply. To ensure dependable operation even in the most demanding environments, the DLRO100 instruments use novel circuitry that gives high noise immunity and guarantees stable readings. For physical protection, they feature enclosures with an IP54 ingress protection rating even when the lid is open and testing is in progress. Operator safety in adverse conditions is assured by a CAT IV 600 V safety rating in line with IEC 61010. With an optional DC clamp, dual ground operation is also supported. DualGround™ greatly enhances safety when working in substations and similar environments by allowing tests to be carried out with both sides of the equipment under test grounded. DLRO100 instruments have a wide range of applications, including checking the resistance of busbar and cable joints, measuring wire and cable resistance, and verifying lightning conductor bonding. They are also well suited for testing switchgear and circuit breakers during manufacture and in the field, and they offer a smooth DC output that is particularly valuable for circuit breaker tests. Instruments in the DLRO100 series have a measuring range of 0.1 µΩ to 1.999 Ω with a resolution of 0.1 µΩ. Results are shown on a large LCD panel and, depending on the model, can also be stored in a large capacity internal memory for later access via the display or downloading via a USB drive. Versions are also available with support for remote operation, Bluetooth connectivity, and asset/result tagging. There are three main models in the series, each have battery and mains power supply:
DLRO100EB is a battery and mains operated unit.
DLRO100XB is a battery and mains operated unit. DualGround capability with optimal clamp and internal memory storage with USB drive download.
DLRO100HB is a battery and mains operated unit. DualGround capability with optimal clamp and internal memory storage with USB drive download. Remote control, asset tagging and Bluetooth®.
Specifications
Frequently Asked Questions
What applications need low resistance testing?
The need for accurate low resistance measurement is very diverse. Typical applications include:Utilities and service contractors - commissioning new installations and regular maintenance testing of: Switchgear and circuit breaker contact resistance Busbar and cable joints Wire and cable resistance Lightning conductor bonding Original equipment manufacturer - detecting manufacturing defects Production test of circuit breakers - contacts and joints Production test of high voltage switchgear Production test of welded joints and connections Transport manufacturing and maintenance Railway rolling stock ground connections and manufactured joints Railway lines and conductor rails - commissioning and maintenance Aircraft frame bonds and static control
What type of instrument should I use for measuring circuit breaker contact resistance?
For the required values in the tens to hundreds of micro-ohms, a general-purpose ohmmeter will not give satisfactory results, even if it can nominally measure the low values of resistance involved. A kelvin type, four-wire measurement is required to calculate the low contact resistance accurately. It’s essential for the instrument to deliver a high test current; IEC requires 50 A or greater, and IEEE requires 100 A or more. A smooth DC output, including ramp up and ramp down of the current, will significantly reduce the potential of an accidental relay trip while testing. Ideally, the instrument should be suitable for use with DualGroundTM test techniques for added safety.
Why 100 A and not 200 A or 10 A?
Megger has a wide variety of micro-ohm test equipment. The general practice for standard circuit breaker applications is to test at 100 A. By designing the unit around this current, the DLRO100 can be compact and lightweight while providing the necessary current to meet the standards. If more current is needed, Megger offers 200 A and 600 A units in the DLRO and MOM series. If you need an even smaller test instrument with test probes, Megger offers several 10 A versions of the DLRO to meet all your testing needs.
What test modes do the DRLO100s have?
All DLRO models offer a choice of test modes. Manual mode allows you to initiate the test once the probes are in contact with the object under test. When you press the test button, the instrument performs a single test. In “Auto” mode, as soon as you connect the potential leads, the test starts automatically. To repeat a test, you must break and remake contact with the potential leads. In “Continuous” mode, you connect the test leads and press the test button. The instrument will continue to test, updating the display after each new test cycle until you press the test button again. With the simple keypad and rotary switches, you can operate all the DLRO100s with work gloves on.
Will the DLRO100 work off mains power if the battery is dead?
If the DLRO100 has the battery option, it can still be operated off of mains power if the battery is dead or low on charge. Note: the charge time is only 2.5 hours if completely dead. So, unless you need to test all day continuously, the DLRO100 can be charged while setting up to provide enough battery to complete your work.
Is the current output of the DLRO100 DC or rectified AC?
During its design, we had circuit breaker testing directly in mind. Therefore, the DLRO100 provides an authentic, smooth DC output with ramp-up and ramp-down current at the beginning and end of the test to minimise unwanted tripping on parallel equipment that is still in service.
Can I use leads that I supply? Do you have different lead lengths?
You can order the DLRO100 with 5, 10, or 15 metre lead lengths that are CAT IV 600 V rated. When other lengths or clamps are required, the DLRO100 has a terminal adapter plug in which a spade-type connector can be attached for custom current cables. The voltage sensing leads use standard banana jacks.
What size is the battery? Can I fly with the equipment?
The DLRO100 is equipped with a user-replaceable, high-power Lithium-ion battery that is less than 100 Wh. This battery meets federal aviation standards for travel, so you can carry the unit on the plane with you if travelling.
