DLRO10HD and DLRO10HDX digital low resistance ohmmeters
Low resistance measurements for the laboratory, the workshop, or the field
Low resistance measurements for the laboratory, the workshop, or the field
Key Benefits
- Advanced safety features
- Battery or mains power supply
- Operable in all weather conditions
- High and low power outputs
Description
The heavy duty DLRO10HD and DLRO10HDX digital low resistance ohmmeters can deliver a 10 A current into circuits up to 250 mΩ and 1 A into circuits up to 2.5 Ω. The duration of each test can be up to 60 seconds, reducing the time required for cooling. These units have a high and low output power selection for condition diagnosis.
The DLRO10HD and DLRO10HDX instruments can be powered from their own sealed, rechargeable lead-acid battery or via mains power. This makes them suitable for continuous testing in repetitive use environments, such as production lines. Additionally, they come in a rugged case designed for stable ground and bench operation. They are IP54 rated when operational and IP65 when the lid is closed, which is ideal for working in all weather conditions.
Both units have five test modes: bidirectional (whereby current reversal with averaging cancels thermal EMFs), unidirectional, automatic, continuous, and inductive. You select the desired mode through a simple rotary control on the mode selection rotary switch. These rotary switches are easy to operate, even with gloved hands, and the instruments’ large, clear, backlit LCD makes for easy reading even from a distance.
The DLRO10HDX has some additional abilities over the DLRO10HD. It is rated CAT III 300 V (as long as the optional terminal cover is fitted to the instrument) and comes with onboard memory storage for up to 200 test results. The memory functions: ‘delete’, ‘download to PowerDB’, and ‘recalling test results’ are also accessible via the range selection rotary switch on this model.
Specifications
Frequently Asked Questions
What can low resistance testing show during electrical manufacturing processes?
The applications for low resistance testing are varied, but some of the most common are: Testing switches, connectors, and relays - to ensure contact resistance is within specified values. Cable resistance - too low shows too much copper in the cable (higher costs), and too high means insufficient copper, so the cable’s current carrying capacity is compromised. Motors and generators - to determine heat rise under load, measure winding resistance, and check for short or open circuits. Fuses - to ensure resistance is within specified values. Cable looms - to check the bonding and interconnections when installing equipment, racks, etc. UPS/car batteries - carrier to plate weld resistance where a high resistance indicates poor weld quality that will restrict the battery’s ability to carry current.
When would you use a low or high power output?
The application and the asset under test will determine whether low or high power is required. Here are three examples: Contamination – The application of high power will result in the test piece heating. Many tests are performed on bonds, connections, and contacts in low-current applications. If you have contamination between surfaces, a higher test current and power will ‘blast’ through the contamination resulting in a good test result, even though the connection will be unreliable in use. Testing with low current and power will reveal the problem much more readily. Rough surfaces – An example where high power is an advantage is testing connections or bonds with rough surfaces. In some such cases, you will obtain a good test result with a low test current and power, with the contact points between contact surfaces being low enough resistance. However, applying a higher test current and power will heat these small points of contact. The result is a changing test result as the heating takes place, highlighting the problem. Frayed wires – On lower current carrying systems (typically less than 10 A), testing with higher power will cause heating on weaknesses such as frayed wired, with the remaining wires presenting a higher resistance. The 25 W power output can be supplied continuously for at least 60 seconds, meaning you can measure resistance with inductance. However, the DLRO10HD/HDX is unsuitable for testing large inductive circuits, such as power transformers.
Why would low resistance testing be used in railways?
The applications for low resistance testing are varied, but some of the most common in the railway industry are: Strap and wire bond between rail segments - for maintaining the performance of control and telephone systems and minimising power loss. Cable joints - for power system efficiency. Earth/ground bonds - to ensure lightning protection on structures and limit step and touch potential on metal floors, handrails, ground mats, metal cladding, platform edge doors, and more.
Why does the DLRO10HD/HDX have high and low power output?
Applying too much current during a test will result in power dissipation in the test piece, which results in heating. The heating alters the resistance of the test piece. However, there are some applications where having a higher output is useful, which is why you can select measurement ranges of either low (0.2 W) or high (25 W) power.
