Cause of failure: confirm whether the power supply voltage is normally output.
Solution: checking whether there is virtual connection in the incoming line; using a multimeter to measure whether the incoming terminal( L+、N- ) voltage of the instrument is normal and conforms with order requirements; Positive and negative should be distinguished in the DC power supply. In addition, pay attention to the output power of the power supply should satisfy relevant requirements.
Cause of failure: electric instrument setting.
Solution: checking whether the setting address and baud rate correspond to the system software. All instruments connected to the same communication channel must ensure that addresses have no overlap and baud rates are consistent.