Factors Affecting Measurement Accuracy of Differential Pressure Transmitter


Release time:

2022-06-29

With the advancement of instrument technology, various brands of differential pressure transmitters are developing in the direction of high precision and intelligence. However, the progress of technology has brought a misunderstanding for designers: when people choose differential pressure transmitter, they often pay attention to the accuracy of differential pressure transmitter, and ignore the factors affecting the measurement accuracy of differential pressure transmitter.

In fact, what users really need is the true value-measurement accuracy that can correctly reflect the measured value, not the accuracy of the differential pressure transmitter itself. There are many factors affecting the measurement accuracy of differential pressure transmitters, some of which are related to environmental conditions and installation methods. What factors affect the measurement accuracy of differential pressure transmitters?automatic controlnet small make up for you to tidy up the following points.

1. Influence of range ratio on measurement accuracy of differential pressure transmitter
The range ratio of the differential pressure transmitter refers to the ratio of the maximum value to the minimum value that the transmitter can measure under the condition of meeting the accuracy requirements. In general, the larger the range ratio, the lower the measurement accuracy, the larger the range ratio of the differential pressure transmitter, which has many advantages. After such an instrument is adjusted, it can be used in many different occasions. However, in practice, the range ratio is too high, which will bring many problems of measurement stability.

Most differential pressure transmitters are within the range of 10:1, and the accuracy is still the reference accuracy and is not affected by the range ratio. However, there are still a considerable number of differential pressure transmitters to ensure the range ratio of reference accuracy is less than 10:1, and this index is even 3:1 and 2:1. Moreover, for different range codes of the same type of products, there may be great differences in the range ratio to ensure the reference accuracy. This is what users should pay special attention to when calculating the accuracy affected by the range ratio.This article is from www.eadianqi.com

2. The influence of temperature on the measurement accuracy of differential pressure transmitter
In the process application of differential pressure transmitter, the process temperature and ambient temperature will change greatly, which will definitely be different from the reference conditions when the transmitter is tested, which also means that the performance will be different from the reference accuracy introduced. The effect of temperature on the differential pressure transmitter is very small when it is close to the maximum range (that is, the small range ratio), but it is very large when it is close to the minimum range (that is, the large range ratio), sometimes even beyond our imagination. According to the comprehensive influence formula of temperature on zero point accuracy and range accuracy provided in some product manuals, if the input maximum range ratio is 100, the influence close to 10% can be obtained.

Some modern intelligent differential pressure transmitter products increase the internal temperatureSensor, Used to correct the thermal effects caused by changes in ambient temperature.

3. Influence of static pressure on measurement accuracy of differential pressure transmitter
Similar to the effects of temperature and span, static pressure has a substantial effect on the accuracy of the zero point and span of the differential pressure transmitter. Such as capacitive differential pressure transmitters, which are almost always affected by static pressure during the operation of the production process system.

When the static pressure of the operating condition exceeds a certain value, the error of the static pressure influence will exceed the accuracy of the transmitter itself. When calculating the channel accuracy of the measurement channel, if the static pressure influence error is added, the channel accuracy requirement may not be met. Therefore, the static pressure influence must be corrected during the calibration of the capacitive differential pressure transmitter.

4. Influence of installation inclination angle on measurement accuracy of differential pressure transmitter
The installation inclination angle refers to the angle between the central axis of the transmitter and the plumb line after the transmitter is installed on the site.

During differential pressure measurement, the detection element senses the pressure difference between the two sides by detecting the deformation and displacement of the center measuring diaphragm. Since the central measuring chamber is filled with silicone oil, when the differential pressure transmitter is inclined along the direction perpendicular to the plane of the measuring diaphragm, the silicone oil itself will generate pressure on the measuring diaphragm, causing the diaphragm to deform, resulting in changes in the output value.

When the differential pressure transmitter is inclined in a direction parallel to the plane of the measuring diaphragm, the filled silicone oil will not press the measuring diaphragm, so there is no effect. Transmitters with different measuring ranges are affected by inclination to different degrees. The smaller the measuring range, the greater the impact. When the differential pressure transmitter tilts forward and backward, its output linearity and output value change are not obvious, which will not affect its normal use. When the differential pressure transmitter tilts left or right, its output value will drift in one direction according to the tilt angle. The larger the angle, the greater the impact, but the linearity will not change significantly.

5. Influence of height difference between measurement point and installation point on measurement accuracy of differential pressure transmitter
Due to the needs of the overall design of the industrial site, the differential pressure transmitter is often not installed near the measuring point in the use of the site, but through the pressure pipe to a more concentrated place, in order to facilitate maintenance and management.

This will cause a height difference between the measuring point and the installation point of the differential pressure transmitter, and the pressure transmission medium in the pressure pipe will generate additional pressure due to the height difference, thus causing an impact and introducing additional errors. In process industry applications, because the density of the medium tends to be large, even a small height difference introduces a large additional error.