What is the zero-point drift issue in level measurement, how is it addressed, and what is its essence?

Don’t try to migrate these two sub-components; think of calculating the range of the liquid level as a math problem – once you do the calculations, it will become clear.

When using differential pressure level measurement, the differential pressure level gauge is not located at the zero level of the liquid. Due to the additional liquid column difference, the signal output of the gauge is not zero when the level is at zero. In such cases, it is necessary to adjust the zero point of the differential pressure level gauge in order to offset this additional liquid column difference; this process is known as zero point adjustment in differential pressure level measurement. When the differential pressure level gauge is below the zero level of the liquid, forward migration is required ； When the differential pressure level gauge is above the zero level of the liquid, it needs to be shifted in the negative direction.

Think of it as 0–50, transformed into -50–0, or 50–100. The range remains the same, but the pressure values on the high and low sides of the differential pressure transmitter change. It is commonly used in double-flange capillary differential pressure transmitters, to adjust the differential pressure range when it is not possible to install the transmitter’s gauge in an ideal position (which is the case in most situations). The specific procedure involves exposing the flanges on the high and low pressure sides to the atmosphere (if there is no fluid inside the container, simply open the root valve). If there is a medium inside the container, disconnect the flanges on the high and low pressure sides as well as the connection bolts and gaskets of the root valve; then use the 475 controller to make the gauge output an analog signal of 0 (i.e., 4 mA) for the current differential pressure value – that’s all that’s needed

The essence of migration is the process of correcting the situation in which the output is not zero (or 4mA) when the input is zero.

What is the essence of migration? ...... It refers to specifying the pressure value corresponding to a liquid level of 0; in other words, it is the pressure value corresponding to the zero point (or the full scale) of the output signal

Not only can the liquid level be transferred, but any analog value can also be transferred. If the measurement is inaccurate, there’s nothing I can do; by transferring it, the measurement will become accurate. ;P