The micro-resistance meter is usually called milliohm meter or micro-ohm meter on the market. The test principle is measured by the four-wire method of the bridge principle (also known as the Kelvin principle abroad), that is, a constant current is applied across the resistance, and then the voltage at both ends is detected by the instrument, and then automatically calculated by the instrument. resistance. The advantage is that the measured data is close to the real resistance value of the resistance in the working state, and the influence of the resistance of the test line itself is eliminated.
Ordinary multimeters generally use the proportional method for measuring resistance. The measured resistance is connected in series with the standard resistance to measure the voltage of the standard resistance and the measured resistance. The currents of the two are the same. The resistance of the measured resistance is calculated according to the resistance of the standard resistance. The actual measurement circuit also uses the voltage corresponding to the standard resistance as the reference voltage, so that the voltage across the measured resistance can be directly measured.
Therefore, when measuring the micro-resistance, the milliohm meter or micro-ohm meter more reflects the true resistance value. The test line resistance of the multimeter will affect the true value of the measured resistance.
For example, to measure a 1 ohm resistance, if the test line of the multimeter itself has 1 ohm, then the displayed resistance value is 2 ohms, do you say this resistance value is real? But milliohm and micro-ohm watches do not have this confusion.
Another very important factor is the test current. The resistance of some resistors under different test currents will change. Universally expressing such a requirement, milliohmmeters and micro-ohmmeters can choose the corresponding constant test current. .
Micro-ohmmeter can be used for aircraft lap resistance test, metal plating resistance measurement, electric welding point detection, connection point detection of electrical grounding system, riveting of metal fatigue cracks and slack, busbar and wire joint detection, mechanical joint detection, connection Precision measurement fields such as cable continuity check and continuity test.