Design of the Apparatus for Detecting and Transmitting Pressure Signals on the Probe of Electrical Impedance Scanning of Breast
In order to explore the relationship between the impact of detection probe and human contact pressure on its imaging result in the electrical impedance scanning techniques of breast, there is a need to design a set of device to extract pressure signal on EIS detection probe and transmit to the host in a long distance. The design uses Wheatstone full-bridge converter based on the resistance-type strain gauge as an extraction method for the pressure signal. After pre-amplification processing of the extracted signals, the voltage signal is converted into 4-20mA of current signal for long-line transmission via XTR106 chip. By the use of digital potentiometer chip replacing the adjustable resistance in the circuit, and by virtue of MCU chip and ADC chip, the system is characterized by automatic zero set of the full-bridge converter of sensor and adaptive control of amplifier circuit gain, thus realizing high-precision measurement and transmission of pressure signal at four locations of detection probes. The simulation and actual measurement results show that, after the automatic “zero set” operation, the output error of the system is less than ± 0.5%; the amplifier gain is within an adjustable range of 75-500, so that the full-scale output error of the system is less than ± 1%. The test results verify the reliability and validity of the system.