Accurate measurement of the resistance of key components in electrical equipment and large industrial environments is crucial. Especially for devices that carry high currents, such as transformers, switchgear, generators, etc., their contact resistance and winding resistance directly affect the operational efficiency, safety, and service life of the equipment. At this point, the "DC low resistance tester" came in handy.
What is a DC low resistance tester?
Simply put, a DC low resistance tester is a precision instrument specifically designed to measure small resistances (typically in the milliohm m Ω range or even lower). It applies a direct current, measures the resulting voltage drop, and then calculates the resistance value of the measured object based on Ohm's law (R=V/I). I chose it because it can provide very accurate and stable readings, unaffected by external interference, especially suitable for measuring devices with low resistance.
What are the factors that affect resistance measurement?
Measuring low resistance is not a simple task, as several factors can "disrupt" and affect the accuracy of the measurement
Contact resistance: Testing whether the contact between the fixture and the object being tested is good, whether there is an oxide layer or dirt, will generate additional resistance.
Temperature variation: The resistance value increases with the rise of temperature, so when measuring, attention should be paid to the ambient temperature, or try to measure at a stable temperature.
Induced voltage: If there is electromagnetic induction in the tested circuit, it may generate additional voltage and interfere with the measurement.
Current size: Although called a "DC low resistance tester", the applied current size can also affect the measurement results, and the appropriate current gear needs to be selected according to the specific equipment.
What tools can help us with precise measurements?
To obtain reliable measurement results, in addition to the "DC low resistance tester" itself, some supporting tools and accessories are also essential:
Four wire test fixture: This is a "miracle tool" for measuring low resistance. It can separate the current circuit and voltage measurement circuit, effectively eliminating the influence of resistance caused by test lines and contact points, ensuring that the measured resistance is the true resistance of the object being tested. Wuhan UHV Power Technology Co., Ltd. provides a variety of high-quality four wire fixtures, providing a solid guarantee for accurate measurement.
Temperature gauge: used to monitor and record the ambient temperature during measurement for temperature correction.
Cleaning tools: such as sandpaper, alcohol, etc., used to clean the contact surface of the tested object and remove the oxide layer.
How to do better DC low resistance measurement?
To obtain more accurate results, you can follow the following steps:
Clean the surface: Carefully clean the contact points of the tested object with sandpaper or cleaning agent to ensure that the metal surface is shiny.
Stable connection: Use a four wire test fixture to ensure that both the current clamp and voltage clamp are in close contact with the object being tested, and the connection is firm.
Choose the appropriate current: Based on the instructions of the tester and the characteristics of the device being tested, select the appropriate measurement current gear. Usually, the larger the current, the more stable the measurement, but attention should also be paid to whether the equipment can withstand it.
Stable reading: Wait for the tester reading to stabilize before recording.
Record temperature: Simultaneously record the ambient temperature during measurement for subsequent analysis.
Wuhan UHV Power Technology Co., Ltd. has been deeply involved in the field of power testing for many years. Its product line covers a variety of high-precision measuring instruments, which can meet the testing needs in different scenarios. Their equipment has gained widespread recognition in the industry for its stability, ease of use, and accuracy.
FAQ
Q: Can a DC low resistance tester measure high resistance? A: Usually not. The DC low resistance tester is designed to measure very small resistance values, while measuring high resistance requires the use of other types of instruments such as a megohmmeter.
Q: Why are the measurement results always different? A: This may be related to poor contact, temperature changes, or incomplete loosening of the testing fixture. Make sure to repeat the 'measure better' steps mentioned above for each measurement.
Q: Is the four line method really better than the two line method for measurement? A: For low resistance measurements, the four wire method can significantly improve accuracy as it eliminates the influence of lead resistance and contact resistance on voltage measurement readings.
Q: What is the required current for testing high current equipment? A: This depends on the specific parameters of the device, and usually the device manual will provide recommended test current ranges. The professional technical personnel of Wuhan UHV Power Technology Co., Ltd. can provide you with more specific suggestions.
Q: What industries is this tester mainly used in? A: Mainly used in the fields of power, electrical manufacturing, railway, metallurgy, aviation and navigation, it is used to test the quality of equipment such as transformers, switches, cables, motors, etc.