1. Investigation method: Review the ignition, smoking, odor, power supply changes, lightning strikes, humidity, misoperation, and incorrect maintenance before the occurrence of the fault. 2. Intuitive method: Observe external damage to the circuit, leakage of pressure pipes, overheating of the circuit, power switch status, etc. 3. Detection method: 1) Circuit detection: Separate the suspected faulty part from other parts and check if the fault disappears. If it disappears, determine the location of the fault. Otherwise, proceed to the next step of search. For example, if the intelligent differential pressure transmitter cannot communicate with Hart remotely normally, disconnect the power supply from the body and use an additional power supply on site to power on the transmitter for communication, in order to check if the cable is overlapped with electromagnetic signals of about 2kHz and interferes with communication. 2) Short circuit detection: Under the premise of ensuring safety, directly short-circuit the relevant circuits. For example, if the output value of the differential pressure transmitter is too small, the pressure pipe can be disconnected, and the differential pressure signal can be directly led to both sides of the differential pressure transmitter from outside the primary pressure valve. Observe the transmitter output to determine the connectivity of blockage and leakage in the pressure pipe. 3) Replacement detection: Replace the suspected faulty parts and determine the faulty location. For example, if there is suspicion of a malfunction in the transmitter circuit board, a temporary replacement can be made to determine the cause. Division detection: Divide the measurement circuit into several parts, such as power supply, signal output, signal transmission, and signal detection. Check by division, from simple to complex, from surface to interior, narrow down the scope, and identify the fault location.