Problems with double-flange differential pressure transmitters
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This post was last edited by zhoudingshengs on 2023-12-3 at 10:16. Please actively participate in the discussion: 1. As shown in the figure below, a double-flange differential pressure transmitter is used to measure the liquid level inside a sealed container; both the zero point and range of the transmitter have been calibrated. Later, due to on-site maintenance requirements, the installation location of the instrument was moved upward by a certain distance. Then, which of the following options is correct? A. Zero point rises, range remains unchanged. B: Zero point drops, but the range remains unchanged. C. The zero point remains unchanged, while the range increases. D. The zero point remains unchanged, but the range decreases. E. The zero point remains unchanged, and the range remains unchanged.
When using a double-flange differential pressure transmitter for level measurement in a closed container, the two pressure input points of the differential pressure transmitter, namely the high-pressure side and the low-pressure side, are usually connected to the liquid level and the top of the container, respectively. Since the pressure generated by a liquid is proportional to its height, a differential pressure transmitter can measure this height difference, thereby indirectly determining the liquid level. When the installation position of the double-flange differential pressure transmitter is moved upward, the height of the instrument above the liquid level increases, which means that the distance between the high-pressure side and the liquid level decreases. Since the function of the double-flange tube is to eliminate the static pressure difference caused by the liquid column in a sealed container, so that the transmitter is affected only by changes in liquid level, theoretically the zero point and range should remain constant, as the double-flange tube automatically compensates for changes in installation position. Therefore, the correct answer is: E, the zero point remains unchanged, and the range remains unchanged. It should be noted that in practice, the moving installation position may be affected by other factors; for example, there might be bubbles or residual liquid in the connection tube from the pressure transmitter to the container’s liquid level, and these can all affect the final measurement results. In practical applications, it is advisable to recalibrate the instrument after moving the double-flange differential pressure transmitter to ensure measurement accuracy. .
E. The zero point remains unchanged, and the range remains unchanged.
Middle school level? ? ? There is a problem with this question. Move up by a paragraph? How long is a segment? H=△P*η. As long as △P remains unchanged, nothing else changes. But as shown in the diagram, does △P remain unchanged? No matter how the transmitter is moved below the high-pressure side, △P remains unchanged; will it also remain unchanged when it is moved above the high-pressure side? Nonsense nonsense
E. The zero point remains unchanged, and the range remains unchanged. The zero-point shift of a double-flange level differential pressure transmitter has nothing to do with the installation location of the transmitter.
Double-flange differential pressure transmitters are used for level measurement; as long as the length of the capillary allows it, they can be installed in any position without affecting their zero point or range! This is a basic skill for instrument operators! But remember, remember well — the transmitter should be installed below the lower flange! Otherwise, it will affect the service life of the instrument!