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Some factors that affect the performance of differential pressure transmitter

Post: 2020-02-29

With the development of instrument technology, various brands of differential pressure transmitters are developing towards the direction of high precision and intelligence.However, the development of technology has led designers to make a mistake: when choosing differential pressure transmitters, people tend to pay attention to their own accuracy and ignore other factors that affect the measurement accuracy.In fact, what the user really needs is to be able to accurately reflect the actual value of the measured value -- the measurement accuracy, not the accuracy of the transmitter itself.There are many factors that affect the measurement accuracy of the transmitter, some of which are also related to the environmental conditions and installation methods.In the design, the accuracy of the product itself cannot guarantee the actual measurement effect. Designers should not only take into account the influence of the actual environment on the accuracy of the product in the selection, but also pay attention to minimize the influence on the accuracy of the transmitter in the installation.So, what are the factors that affect the differential pressure transmitter?Following is a brief introduction of hanga technology, which focuses on the r&d, production, sales and service of various intelligent pressure transmitters, various measurement and control system software and Internet of things applications for many years:

1. Influence of range ratio

The range ratio of the differential pressure transmitter is the ratio of the maximum value and the minimum value that the transmitter can measure under the condition of satisfying the accuracy requirement.In general, the larger the range ratio, the lower the measurement accuracy, the larger the range ratio of the pressure transmitter, there are many benefits, such a meter after adjustment, can be used in many different occasions.However, if the ratio of measurement range is too high in practice, it will cause many problems of measurement stability.

Most differential pressure transmitters are in the range of 10:1 range ratio, and the accuracy is still the reference accuracy, which is not affected by the range ratio.However, there are still a considerable number of differential pressure transmitters to ensure that the range ratio of reference accuracy is less than 10:1, and this index is even 3:1 and 2:1.And the same model of products with different range code, to ensure that the reference accuracy of the range ratio may also be very different, this is the user in the calculation of the accuracy affected by the range ratio need to pay special attention to.

Second, the influence of temperature

In the process application of differential pressure transmitter, the process temperature and ambient temperature will change greatly, which will certainly be different from the reference conditions of the transmitter test, which also means that the performance will be different from the introduced reference accuracy.The influence of temperature on the differential pressure transmitter is small when it is close to the large range (i.e., small range ratio), but large when it is close to the minimum range (i.e., 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 large range ratio is 100, the influence of nearly 10% can be obtained.Some modern intelligent pressure transmitters have added internal temperature sensors to correct for thermal effects caused by changes in ambient temperature.

The influence of static pressure

Similar to the influence of temperature and range, static pressure has substantial influence on the zero point and range accuracy of the transmitter.As capacitive differential pressure transmitter, the transmitter in the process of production technology system to run, almost always influenced by the static pressure, when the operation condition of the static pressure exceeds a certain value, the static pressure affecting the precision of the error will exceed the transmitter itself, the precision of measurement channels for calculation, if add static error, the accuracy requirement may not be able to meet the channels, so the capacitive differential pressure transmitter when checking must effect of static correction.

Influence of installation tilt Angle on transmitter

Installation tilt Angle refers to the Angle between the central axis of the transmitter and the plumb line after the transmitter is installed on site.

When the pressure difference is measured, the detecting element senses the pressure difference between the two sides by measuring the deformation displacement of the diaphragm in the detecting center.As the central measuring room is filled with filled silicone oil, when the differential pressure transmitter tilting along the direction perpendicular to the measuring diaphragm plane, the filled silicone oil itself will produce pressure on the measuring diaphragm, causing deformation of the diaphragm, resulting in the change of the output value.When the differential pressure transmitter is inclined in a direction parallel to the measuring diaphragm plane, filling silicone oil will not compress the measuring diaphragm and therefore has no effect.The influence of tilt is different for transmitters of different range. The smaller the range, the greater the influence.When the differential pressure transmitter tilts forward and backward, its output linearity and output value do not change obviously, 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 influence of height difference between measurement point and installation point

With the need of the overall design of the industrial field, the differential pressure transmitter can not be installed near the using field measurement point, but by lead pressure pipe pressure to a relatively centralized place, so that the maintenance and management, which can cause point height difference between the measurement point and installation of the guide pipe of the pressure medium can produce additional pressure due to the difference in height, thus influence, attract additional error.In process industrial applications, the medium density is often larger, so even a small height difference, the introduction of additional error is large.