| Psychological test is a comprehensive technology composed of physiology electronics and psychology,and analyzes the psychological state of the testee by means of electronic measurement technology.The psychological tester is also called a multichannel physiological parameter measuring instrument.It is an electronic measuring device based on the measurement of physiological signal changes.This device can record various physiological parameter information of the human body.With the development of society,multi-channel physiological parameter measuring instruments have been widely used in many industries,including the detection of criminal cases in public security,psychological intervention of personnel,political assessment of special occupations such as the military,and personnel recruitment in enterprises and institutions.The current multi-channel physiological parameter measuring instrument has the problems of high cost,low acquisition accuracy,slow acquisition speed,complicated power supply,and RS232 interface used in communication.In order to solve the problem of high cost,through investigating a large number of component products,comparing the performance and price of the components and selecting the cost-effective components.By designing a digital program-controlled constant current circuit on the hardware,the driving characteristics of the heart rate measurement sensor are improved.At the same time,the closed-loop detection of the excitation light source and the collected signal is realized on the software.Compared with the traditional open-loop detection signal,the integrity is improved.In the software,the comprehensive algorithm of detecting the slope change of the signal and the time allows the position of the main peak wave to be correctly identified under complex signals,thereby accurately calculating the heart rate.In the skin resistance measurement,by improving the circuit mode of the previous fixed range measurement,the circuit hardware for multi-range digital switching is designed to increase the measurement dynamic range to 20 megaohms.By cooperating with the oversampling technology and automatic range switching algorithm on the software,The measurement error can be controlled within 2%.In the power supply circuit,the external independent power supply mode is improved.Both power and data are transmitted through the USB data line.A complex power supply system capable of generating multiple voltages of 8V,±5V,3.3V,2.5V,etc.is designed inside the system to achieve external The power supply is simple and convenient to use.Using high-speed STM32F407 microprocessor,the sampling rate of 5 channels is increased to 500 Hz,and the measurement result is transmitted to the upper computer in real time through the USB data line.By improving the design of the hardware and optimizing the coordination of the embedded software algorithm,all the details of physiological changes can be recorded,which has an important role in the later analysis.By cooperating with the host computer driver,it can realize the long-term data storage function in hours,which lays the foundation for later information analysis.In this paper,starting from the overall scheme design,optimizing the software and hardware design details,after component selection,scheme verification,research and design of this article's low-cost,high-precision,5-channel human physiological parameter measuring instrument. |
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