With the development of social industrialization, the application range of differential pressure transmitters is becoming increasingly wide, and there are more and more problems encountered in production. In addition, the differences in the level of installation, use, and maintenance personnel make it difficult to quickly solve the problems that arise, which to some extent affects the normal progress of production and even threatens production safety.

1、 The working principle of differential pressure transmitter: The differential pressure from the double-sided pressure pipes directly acts on the isolation diaphragms on both sides of the transmitter sensor, and is transmitted to the measuring element through the sealing liquid inside the diaphragm. The measuring element converts the measured differential pressure signal into the corresponding electrical signal and transmits it to the converter. After amplification and other processing, it becomes a standard electrical signal output. 2、 Several application measurement methods of differential pressure transmitters:

1Combined with the throttling element, measure the liquid flow rate using the differential pressure value generated before and after the throttling element.

2Measure the height of a liquid by utilizing the pressure difference generated by its own gravity.

3Directly measure the pressure difference of liquids in different pipelines and tanks.

3、 Fault diagnosis and analysis in applications: During the measurement process of transmitters, some faults often occur. Timely diagnosis, analysis, and handling of faults are crucial for ongoing production. We have summarized and categorized some judgment analysis methods and analysis processes based on our daily maintenance experience.

1Investigation method: Review the ignition, smoking, odor, power supply changes, lightning strikes, humidity, misoperation, and incorrect maintenance before the occurrence of the fault.

2Intuitive method: Observe external damage to the circuit, leakage of pressure pipes, overheating of the circuit, power switch status, etc.

3Testing method:1)Open 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, such as differential pressure transmitter not functioning properlyHartRemote communication can be achieved by disconnecting the power supply from the body and using an additional on-site power supply to power on the transmitter for communication, in order to check if the cables are stacked2kHzInterference with communication caused by electromagnetic signals.

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 or leakage in the pressure pipe.

3)Replacement testing: 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.

4)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.

4、 Fault analysis of several typical measurement circuits

The following only takes the example of a pressure pipe fault to analyze the measurement circuit fault of a differential pressure transmitter.

1.Blockage of pressure conduit:

In instrument maintenance, due to the transmitter'>It is common for the positive and negative pressure pipes of differential pressure transmitters to become blocked due to delayed discharge of the pressure pipes, or due to dirty or sticky media.

When the actual traffic isFReduce toFLater, the static pressure in the pipeline also decreases accordingly, with a decrease value ofP0Meanwhile, when the actual traffic drops toFLater on,The P-value also needs to increase due to the decrease in fluid flow velocity inside the pipe, and the increase value is set as P0’That is: △P=（P+-P0）-（ P-+P0At this point, the output value of the transmitter should decrease.

2.Positive pressure pipe leakage:

In fact, when the leakage is very small, due to various reasons, it is difficult for process operators or instrument maintenance personnel to detect it. Only when the leakage is large and there is a significant error between the measured flow rate and the actual flow rate will it be discovered, even if the actual flow rate increases.