Single arm bridge

There are many applications of electric bridges. The general application is Wheatstone single-arm electric bridges. The resistance of each arm is used to judge the size of the physical quantity by the degree of imbalance of the bridge (bridge current or voltage), such as strain gauges and so on.

1. What is a single arm bridge

The single-arm bridge was once called the Wheatstone bridge. Resistors R1, R2, R3 and R4 are connected to form a quadrilateral. One diagonal ab of the quadrilateral is connected to a DC power supply G via the button S, and a galvanometer is connected to the other diagonal cd as a zero-pointer. After turning on the button S, adjust the standard resistances R2, R3 and R4, the galvanometer’s indication is zero, even if the bridge is balanced, the value of the measured Electronic R2 can be calculated based on the known standard resistances R2, R3 and R4 . During measurement, a certain ratio arm can be selected according to a rough estimate of the measured resistance, and then the comparison arm can be adjusted to balance the bridge. Then the value of the comparison arm multiplied by the multiple of the ratio arm is the value of the measured resistance.

2. The working principle of a single-arm bridge

The single-arm bridge is powered by a constant current source, so that the output of the bridge is not affected by temperature. After the single-arm bridge detects the change in resistance, it passes through a differential amplifier, and the output signal is converted into a corresponding current through voltage and current conversion. The current signal is compensated by the nonlinear correction Circuit, that is, a linear relationship with the input signal is generated. DC4~20mA standard output signal. When stress acts on the semiconductor material, in addition to deformation, the resistivity of the material also changes. This phenomenon of changing the resistivity of the material due to stress is called the piezoresistive effect.

3. Measuring range of single arm bridge

The single-arm bridge is suitable for measuring the resistance of medium resistance value (10～10^6 ohm). If you want to measure a larger resistance, a high-resistance bridge or a megohmmeter is generally used; and if you want to measure a smaller resistance, a double-arm bridge (Kelvin bridge) is generally used.

The bridge has high accuracy and good stability, so it is widely used in electromagnetic measurement, automatic adjustment and automatic control. The Wheatstone single-arm bridge is the most basic DC single-arm bridge. DC single-arm bridge circuit.