So, you need to learn how to do level calculation for a pressure transmitter with capillary? Here’s what you need to know.

Level calculation never changes on a differential pressure transmitter; once you understand the equation, you can do any other range calculation. Now, there are several types of DP pressure installations to level measurement; I’ll give you a step by step based on your problem.

Level calculation for capillary system

Level calculation for pressure transmitter with capillary
Example sent by the customer

Level at 0%

  • HP – LP
  • (Height H side x Capillary density) – (Height L side x Capillary)
  • (1000 x 1.02) – (6000 x 1.02)
  • 1020 – 6120
  • DP0% = – 5100 mmWC

Level at 100%

Also, it is important to understand the composition of a differential pressure transmitter. It is composed of a sensing cell (pressure sensor) and a transmitter. The cell has two pressure chambers separated by a diaphragm.

We call one chamber the high-pressure side and the other the low-pressure side, but we don’t have to take that literally. It just tells us the direction of the impact that pressure will have on the output signal.

Capillary vs electronic sensor

Electronic sensors can serve as cheaper alternatives to capillaries. Here’s a quick comparison.

The pressure transmitter will work with both a capillary or electronic remote sensor, but the installation with capillary has limitations that electronic sensors can solve and vice versa.

Capillary or electronic remote sensor
Level measurement – Courtesy of Emerson Automation Solutions

For instance, a bad setup, like a loose or bent tube, can reduce capillary accuracy. Wet capillaries can also clog and need cleaning. Remote electronic sensors bring a few advantages to the end-user. They have much easier setups, as you have no tubes to kink or clean and no cables to wrap.

Endress+Hauser
Level measurement – Courtesy of Endress+Hauser

However, they have a couple of drawbacks too. They cost more, for one. And, usually, these sensors can’t hold up to high temperatures because of their electronic bits. You’ll have to review your application to decide which would work best for you.

To know more about level calculation for pressure transmitter, please ask our engineers!

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