Level and pressure

Find some information to understand what positive transfer and negative transfer are, when they are used and when not. As for the equipment needed for verification, such as pressure pumps… learn more about it*

If a gauge has its range set, how can it be transferred? Could you tell me about positive and negative transfer?

When setting the zero point, empty the medium in your container; use the bottom flange as the zero point, and set the transmitter’s current pressure to the lower limit of the range. You need to understand the issue of positive and negative transfer; in fact, most of the cases we encounter are those involving negative transfer. I suggest you buy a collection of test questions for field instrument technicians and take a look at it

Can someone send me some learning materials on transmitters?

Measure the liquid level using a double-flange transmitter. When installing a double-flange transmitter for level measurement, the negative pressure chamber should be placed at the upper end, the positive pressure chamber at the lower end, and the instrument body in the middle. This arrangement creates a negative differential pressure; if this value is not too high, it can be eliminated by zeroing the transmitter. However, when a certain value is reached, negative migration can be used to eliminate it. It should be noted that the magnitude of the negative migration depends only on the height difference between the two flanges and the height H0 of the constant liquid level, and is unrelated to the elevation at which the transmitter is installed.

The calibration that does not use zero pressure as the zero-point input for the transmitter is referred to as positive and negative drift. The adjustment when the input pressure is below zero pressure is called negative migration. Adjustment with an input pressure higher than zero pressure is called positive migration. The simplest way to adjust the positive and negative offset of a transmitter is to first perform calibration by setting zero pressure as the transmitter’s zero point, and then use the zero adjustment screw to adjust the zero point accordingly in both positive and negative directions. Give examples to illustrate positive and negative transfer. Assuming the range to be calibrated is 5 kPa to 30 kPa, the calibration steps are as follows: 1. Calibrate the transmitter at 0–25 kPa. 2. Apply a 5 kPa signal to the high-pressure side of the transmitter, then adjust the transmitter’s zero point until the output is 4 mA. Note: The range cannot be adjusted.

Here, I would like to introduce a simple and quick method for setting the range of a double-flange level transmitter: When installing a double-flange level transmitter at two different locations, it is necessary to remove the pressure acting on the positive and negative flanges, so that both flanges are under atmospheric pressure. 1. The current pressure value ΔP represents the lower limit of the range; 2. The upper limit can be calculated using the formula P=ρgh. △P is the upper limit of the range, ρ is the density of the medium being measured, g is the local gravitational acceleration, and h is the distance between the two flanges. I have encountered situations where the level transmitter is shifted forward, and forward shifting is used when measuring the liquid level in gas tanks! The method is the same as the one described above, hehe···

1. Use a double-flange transmitter to measure the liquid level. 2. The calibration that does not use zero pressure as the zero-point input for the transmitter is referred to as positive and negative offset. Note: The range cannot be adjusted. 3. For double-flange level transmitters, when installed at two locations, the pressure acting on the positive and negative flanges is removed to keep both flanges under atmospheric pressure: (1) The current pressure value ΔP represents the lower limit of the measurement range; (2) The upper limit is calculated using the formula P=ρgh. △P is the upper limit of the range, ρ is the density of the medium being measured, g is the local gravitational acceleration, and h is the distance between the two flanges.