Precision bridge isolation measurement amplifier circuit composed of INA102

The bridge measurement isolation amplifier circuit composed of ISO102 and low-noise and low-power INA102 is widely used in industrial process control, as shown in the figure. ISO102 is a capacitive coupling buffer isolation amplifier circuit. The gain of INA102 is set to 1000, which mainly amplifies the 300Ω bridge signal. The power supply of the bridge is completed by two parts: one part is provided by the power supply end (pin 12 of INA102) through a 680Ω resistor to provide l4mA current; the other part is provided by the 5V reference excitation of ISO102 to provide 2.7mA current. The sum of the two is 16.7mA, which powers the bridge. The change signal of the bridge is directly input to the differential input end of INA102. The isolation amplification of the bridge signal and the output voltage Uo is realized. The power supply of the entire measurement circuit is provided by DC/DC conversion devices such as PWS725A or PWS726A, so that the isolated parts do not share the same ground and power supply. This circuit is directly used to accurately measure physical quantities such as pressure, weight and strain.