In scientific research, weak signals are often indispensable, and because of the characteristics of the signal and the surrounding noise may be large, the requirements for the signal processing circuit are high. In this paper, a circuit for DC weak signal detection is designed, and its main module circuit composition and electrical performance are introduced.
Research on DC Weak Signal Detection System Based on ADS1256---Measurement System CompositionAccording to the measurement requirements of weak signals, the system consists of multi-stage amplification and filtering modules. The module structure is shown in the figure below.
The filter circuit is a circuit commonly used in signal processing. Its main function filters the target signal and useful part of the input signal, and filters out the noise part and the unwanted signal in the input signal. This section sets up a second-order passive low-pass filter. This filter consists of resistors and capacitors, but requires lower source impedance and higher load impedance. This filter is located at the front of the amplifier and performs a primary processing of the signal. The circuit schematic is shown below.
Its transfer function is:
After the signal is amplified, a first-order active filter circuit is connected to further filter the signal.
Its transfer function is:
Its circuit schematic is:
The AD conversion circuit uses TI's low noise high resolution 24-bit analog-to-digital converter ADS1256. In the circuit designed in this paper, ADS1256 is used for DC weak signal acquisition, the voltage reference is 2.3V, and the minimum measurement accuracy is up to 1uV. The average method is used to collect the sampled data within 1 s and average it to improve the accuracy of the data. The schematic diagram of the AD conversion part circuit is shown below.
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