The basic principle of a DC resistance tester is to use a central control unit to control a constant current source, apply a constant, high-precision current to the external load under test, then collect data such as the test voltage and the current test current, and obtain the actual resistance value after processing. According to this principle, whether the selected instrument can measure accurately depends on whether the current output capability and range of the selected instrument cover the resistance interval of the object under test. Design and selection personnel can start by checking the following questions.
Q: Should I first look at the resistance range of the object under test, or first look at the test current?
The two need to be judged in conjunction. The resistance range of the equipment under test determines the coverage capability of the instrument range, while the required test current determines whether sufficient resolution and signal-to-noise ratio can be obtained at that resistance. Low-resistance loads such as transformer windings, switch contacts, and cable conductors often have resistance values in the milliohm to ohm range. If the test current is too small, the voltage drop signal will be weak, and reading stability will decrease; if the current is too large, it may exceed the instrument output capability or cause heating effects. During selection, the maximum and minimum resistance values that may occur on site should be listed at the same time, and then check whether the current output of the instrument within this interval is adjustable and whether the ranges are reasonably divided.
Q: How much impact do power supply conditions have on on-site use?
The constant current source requires stable power supply support to operate. If only temporary power is available on site or voltage fluctuations exist, attention should be paid to the instrument's adaptability range to power supply conditions and whether it has the necessary protective measures. For different occasions such as substations and maintenance workshops, power supply capacity and grounding conditions differ significantly. During selection, incorporating the power supply method and cable length into consideration can reduce situations where normal output cannot be achieved after arriving on site.
Q: Is size and weight worth paying attention to?
Yes. Taking common specifications among such products as an example, the overall length is about 180 mm, and the weight is about 5 kg (including test clamps and test leads), making it an instrument that needs to be transported and wired on site. The length and clamping method of the test clamps and test leads directly affect wiring efficiency and contact resistance. During selection, the terminal positions of the object under test and the working space can be combined to confirm whether the accessory configuration meets on-site operating habits.
Q: How should data reading and recording methods be considered?
On the premise of meeting range and current matching, then pay attention to display method, data storage, and export functions. For work requiring multiple measurements and trend comparison, functions that facilitate recording and review are more practical; for single-point rapid measurement, simple operation and stable readings are sufficient. Parameter information can refer to the technical indicators marked in the product materials. The above information and technical parameters are sourced from Yangzhou Darui Electric Co., Ltd. and are compiled and released by it. Actual selection should still be based on the on-site object under test and power supply conditions.
