DP Transmitter Working Principle and Its Fault Diagnosis Method

1. Working principle of differential pressure transmitter

The differential pressure from the double-sided pressure guiding tube directly acts on the two-sided isolation diaphragm of the transmitter sensor, and is transmitted to the measuring element through the sealing liquid in the diaphragm. The measuring element converts the measured differential pressure signal into a corresponding The electrical signal is transmitted to the converter, and after amplifying and other processing, it becomes a standard electrical signal output. Several application measurement methods of dp pressure transmitter:

(1) Combined with the throttling element, the liquid flow rate is measured by the differential pressure generated before and after the throttling element.

(2) Use the pressure difference generated by the gravity of the liquid to measure the height of the liquid.

(3) Directly measure the pressure difference of different pipelines and tank liquids.

2. Fault diagnosis of differential pressure transmitter

Differential pressure transmitters often have some faults during the measurement process. The timely determination, analysis and treatment of faults are vital to ongoing production. Based on the experience in daily maintenance, we have summarized some judgment analysis methods and analysis procedures.

(1) Investigation method: Review the sparking, smoke, odor, power supply changes, lightning strikes, humidity, misoperation, and mismaintenance before the failure.

(2) Intuitive method: Observe the external damage of the circuit, the leakage of the pressure guiding tube, the overheating of the circuit, the status of the power supply switch, etc.

(3) Detection method:

Short-circuit detection: Under the condition of ensuring safety, directly short-circuit the relevant part of the loop. For example, if the output value of the differential transmitter is too small, the pressure guiding tube can be disconnected, and the differential pressure signal can be directly led from the primary pressure valve. Go to both sides of the differential pressure transmitter and observe the output of the transmitter to determine the plugging and leaking connectivity of the pressure guiding pipeline.

Open circuit detection: Separate the suspected faulty part from the other parts to check whether the fault disappears. If it disappears, determine the fault location, otherwise you can proceed to the next search. For example, if the intelligent differential pressure transmitter cannot communicate normally, you can The power supply is disconnected from the main body of the instrument, and the transmitter is energized for communication with an additional power supply on site to check whether the cable is superimposed with an electromagnetic signal of about 2kHz and interferes with the communication.

Replacement detection: replace the suspected faulty part and determine the faulty part. For example, if it is suspected that the transmitter circuit board is malfunctioning, one can be temporarily replaced to determine the cause.

Subsection detection: divide the measurement loop into several parts, such as: power supply, signal output, signal transmission, signal detection, check by subsection, from simple part to the complex part, from the outside to the inside, narrow the scope, and find the fault location.