1. Firstly, the sensor's power supply voltage is determined according to the label of the sensor, and the output mode is wired according to the corresponding interface mode, and the corresponding protocol is used;

2. Use a multimeter to check the power supply voltage to ensure that the power supply is normal;

3. Configure the serial port parameters for communication, set the correct product address (normal protocol factory default 00, modbus protocol factory default 01), select the correct baud rate (default 9600), open the computer device manager to confirm that the COM port number is selected correctly;

4. Use the replacement method, replace the serial cable, or test the product;

Note: Quickly identify the normal working state of the product: Under normal power supply, use a multimeter to measure the current on the red line of the product. The digital sensor is typically 40ma, and the maximum value of the analog output sensor is not more than 60mA.