The principle of measuring resistance by bridge method The bridge circuit is a basic circuit connection method in electromagnetic measurement. It is widely used because of its sensitive test, accurate measurement and convenient use. Bridge can be divided into DC bridge and AC bridge, DC bridge is mainly used to measure resistance. DC single bridge, usually called Wheatstone bridge, is used to measure the median resistance in the range of1~106 W.

DC double bridge, usually called Kelvin bridge, is used to measure the low-value resistance in the range of10-3 ~1w. Besides measuring resistance, AC bridge can also measure capacitance, inductance and other electric quantities. Some non-electric quantities, such as temperature and pressure, can also be measured by sensors, which are widely used in non-electric quantity measurement methods.

Preventive measures against resistance

Before use, the resistance should be checked, and checking its performance is to measure whether the actual resistance is consistent with the nominal value and whether the error is within the allowable range. The method is to measure the resistance with a multimeter. Pay attention to two points when measuring, and determine the range according to the measured resistance value, so that the pointer is indicated in the middle of the scale line for easy observation.

After determining the resistance range, the zero point should be adjusted. The method is to short-circuit the two probes (direct collision), adjust the zero adjustment device to make the pointer accurately point to the "0" of the Ω scale line, and then measure the resistance value of the resistor. In addition, be careful not to touch the two ends of the resistor or the metal part of the stylus, otherwise it will cause test errors.