The data acquisition circuit consists of three parts: the Holzer sensor UGN3503, the amplifier circuit and the peak detection circuit.
Because the voltage signal Holzer sensor UGN3503 collects the signal to a millivolt signal, the signal strength is very weak, so, before the first amplification, after a peak detection circuit to transform the range of input voltage signal is converted to analog to digital converters for the (0-5 V). The signal amplifying circuit with high input impedance, low drift, integrated operational amplifier common mode rejection ratio is LM324.LM324 four LM324 four operational amplifier integrated circuit, amplifier circuit has a wide range of power supply voltage, low static power consumption, the use of single supply, low price, so it is widely used in a variety of circuit. It uses a 14 pin dual in line plastic packaging, appearance is shown in the figure. It contains four Operational Amplifiers group the same form, shape and pin arrangement as shown below