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Differential Pressure Transmitter Static Pressure Error Causes and Solutions

The main reasons for the differential pressure transmitter static pressure error: 1, caused by the positive and negative pressure chamber membrane box is not equal to the effective area. At the same pressure, the resultant force on the bellows is not zero, and therefore an additional moment M is generated, which shifts the main lever position and causes zero drift. The magnitude of the moment M, can be obtained by the following formula M: APL type △ A - the difference between the effective area of the two sides of the membrane box P-static pressure L - the distance from the end of the main lever to the sealing diaphragm. The differential pressure transmitter's differential pressure scale is usually calibrated under the condition that the negative pressure chamber is open to the atmosphere. When it is installed to the site to actually use the static pressure zero calibration, the zero output and the negative pressure chamber are often found to have atmospheric proof. The zero output is inconsistent. The zero position where the positive and negative pressure chambers pass into the same static pressure and deviate from the zero position when passing through the atmospheric verification is called a static pressure error.
If the differential pressure transmitter's static pressure error is not corrected, it will bring error to the flow measurement, and it will have a more significant impact when the relative flow rate is small. Therefore, we must correct the static pressure error before putting it into use. The specific correction method is as follows:
The method is to pass the same static pressure to the positive and negative pressure chambers, one of the three valve groups high and low pressure valves is opened, the other is closed, and the balance valve is opened. If it is suspected that the positive and negative pressure chambers are not filled with the measured medium yet, The vented (or drained) valve on the positive and negative pressure chamber drains the product gas (or fluid) and then checks the differential pressure transmitter output. By this method, the static pressure error can be completely eliminated, so that the accuracy of the differential pressure transmitter can be guaranteed.

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