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First, the working principle of the pressure transmitter: differential pressure from the two side pressure tube directly acting on the transmitter sensor diaphragm on both sides of the diaphragm, through the diaphragm seal liquid conduction to the measuring element, the measuring element will test The resulting differential pressure signal is converted to its corresponding electrical signal for transmission to the converter, which is then converted to standard electrical signal output through amplification.
Second, the pressure transmitter of several applications measurement methods:
1. In combination with the throttling element, the differential pressure value generated before and after the throttling element is used to measure the liquid flow.
2. Using the pressure difference generated by the liquid's own gravity, measure the height of the liquid.
3. Directly measure the pressure difference between different pipes and tanks.
Third, the application of the fault diagnosis and analysis: the transmitter in the measurement process, there will often be some failures, faults, timely determination and analysis of the treatment, for the ongoing production is critical. Based on our experience in routine maintenance, we summarized some judgment analysis methods and analysis procedures.
1. Investigation Method: Review the fire, smoke, odor, power supply change, lightning strike, moisture, misoperation, and mis-maintenance 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, and the status of the power switch.
3. Detection method: 1) Disconnection detection: Separate the suspected faulty part from other parts to see if the fault disappears. If it disappears, then determine the fault location, otherwise you can find the next step, such as: the pressure transmitter can not Normal Hart remote communication can disconnect the power supply from the watch body and use the on-site power supply method to power on the transmitter to check whether the cable is overlaid with an electromagnetic signal of about 2 kHz to interfere with communication.
2) Short-circuit detection: In the case of ensuring safety, the relevant part of the circuit is short-circuited directly, such as: the output value of the differential transmitter is too small, the pressure-conducting tube can be disconnected, and the differential pressure can be directly from the pressure-receiving valve at one time. The signal is directly led to both sides of the pressure transmitter and the output of the transmitter is observed to determine the plugging and leakage connectivity of the pressure-conducting pipeline.
3) Replacement test: Replace the suspected defective part and determine the fault location. For example, if you suspect that the transmitter circuit board has failed, replace it temporarily to determine the cause.
4), Division detection: The measurement circuit is divided into several parts, such as: power supply, signal output, signal transmission, signal detection, according to sub-section inspection, from the simple to the complex, from the table and in, narrow the scope, find out Fault location.
Fourth, the failure analysis of several typical measuring loops The following takes the pressure guiding tube fault as an example to analyze the pressure transmitter measuring circuit fault.
1. Pressure tube plugging:
In instrument maintenance, due to the transmitter's> pressure transmitter pressure tube discharge is not timely, or the media is dirty, sticky and other reasons, positive and negative pressure tube clogging is a common occurrence.
When the actual flow rate decreases from F to F, the static pressure in the pipeline is reduced accordingly. The reduction value is set to P0. At the same time, when the actual flow rate drops to F, the P-value also depends on the flow rate of the fluid in the pipe. Decrease and increase, set the increase value to P0'. That is: â–³P=(P+-P0)-(P-+P0') The transmitter output value should be reduced at this time.
2. Positive pressure pipe leakage:
In fact, when the amount of leakage is very small, it is difficult for technicians or technicians to find out because of various reasons. Only when the leakage is large and the measured flow has a large error compared with the actual flow, it will be discovered. Even when the actual traffic rises.
Fault diagnosis and analysis of pressure transmitters in applications
Fault Diagnosis and Analysis of Pressure Transmitters in Application With the development of social industrialization, the application of pressure transmitters has become more and more extensive, and more and more problems have been encountered in production, coupled with the installation, use and maintenance of personnel. Differences in levels have caused problems that cannot be resolved quickly, affecting the normal production of production to a certain extent, and even precipitating production safety.