Weak Current Signal Detection Device Based on Embedded System

The current rapid development of weak electrical installations has made the monitoring of weak signals increasingly important. For highly sophisticated instruments, the slightest signal deviation will cause terrible and irreparable damage. At present, commercially available multimeters generally have low accuracy, which does not meet the error range required for weak electrical signal monitoring, because it cannot be monitored in real-time, and requires manual handheld data collection. To address the above demands, this study designs and builds a voltage and current signal collector based on the STM32F103 microcontroller. In this case, the DC voltage is designed in the range of −5 V to 5 V, and for the current is from 4 to 20 mA, and the AC voltage from 0 to 5 V can be measured. The measurement results will be displayed on the LCD screen. The collector uses RS485 as the physical transmission interface and the communication protocol uses the Modbus-RTU protocol, which can work properly in the range of 10–24 V DC supply. The analysis of the corresponding requirements is followed by the circuit design to complete the transmission and display of the collected data. The DC voltage measurement part contains the process of boosting and dividing the circuit and then reading it, the current measurement is completed by an isotropic proportional amplifier circuit, and the AC voltage RMS measurement uses the AD637 true RMS conversion chip to realize the circuit, the design contains the software part, the hardware part, and the communication part design. The final device has been tested to meet the national standard of maximum permissible error range within ±0.1 and is suitable for the complex environment envisaged.