Pressure measurement and AD conversion circuit using single power supply

In portable measuring instruments, it is often inconvenient to use AC power. In this case,
a negative power generator must be added to the measurement circuit using dual power supplies. The circuit as shown in the figure uses a single power supply for pressure measurement and A/D. Conversion
circuit, its function is to amplify the sensor measurement signal to 0~5V and then convert it into a digital signal (A/D conversion).
    The output signal of the pressure sensor measuring bridge is sent to the ① and ② pins of the IC. After internal amplification, it outputs a voltage of 0~5V, and
then sent to the A/D converter IC3 for analog-to-digital conversion, and finally outputs an 8-bit digital signal. The gain of the circuit is 333.3 (because
pin ⑩ is grounded), and RP adjusts the bridge excitation voltage so that the output voltage is 0~5V (because the maximum input voltage of digital circuits is generally
5v).
    Since the 1832 needs to work under dual power supply conditions, a multivibrator composed of a timing circuit 555 is introduced. The
oscillation output signal is coupled through C3 and rectified by VDJ and VD2 to form a DC negative voltage on C2, which serves as the negative voltage of IC1.
power supply.