Effect of Air Bubble on Differential Pressure Measurement

In summary, the presence of air bubbles in a transmission line can have several negative effects on the accuracy of differential pressure measurements using an electronic transducer. These include process noise, offset errors, and potential system interaction. It is important to properly purge the transmission line before measurement to avoid these issues. If air bubbles are still present, it is best to consult the manual or application engineers for the specific transducer to determine the potential impact on measured values.
  • #1
can12345
22
0
What is the effect of air bubble in transmission line when measuring differential pressure by the using an electronic transducer? Purging is a must before measurement, however if we still have some bubble inside the transmission line or in front of transducer diaphragm, how it may effect to my measured values?
 
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  • #2
can12345 said:
What is the effect of air bubble in transmission line when measuring differential pressure by the using an electronic transducer? Purging is a must before measurement, however if we still have some bubble inside the transmission line or in front of transducer diaphragm, how it may effect to my measured values?

This is probably a question best addressed in the manual for the pressure sensor or by the application engineers at the company that made it.

You are asking (in essence), "How much is it going to hurt if I do not follow instructions?" That depends a lot on the specifics of the device which you have not provided, and I would tend to be skeptical of answers that do not have knowledge and experience with that specific transducer.
 
  • #3
Three effects, two for sure and one maybe...

1. Process noise
To transmit pressure from one end of the tube to the other takes very little time so long as the contents of the tube are incompressible.
Short term fluctuations in system pressure should arrive at both sides of your dp sensor simultaneously so they'll cancel out.
An air bubble in one line delays transmission of pressure to that side, so system pressure fluctuations appear briefly as differential pressure . The sensor obediently reports derivative of system pressure in addition to whatever you're trying to measure, usually liquid level or flow.

2. Offset...
Draw the system and write Kirchoff's Pressure Law around it.
A bubble in a horizontal run does not add or subtract any head
but a bubble in a vertical segment of the tube adds error to your dp measurement in amount g*hbubble*(ρliquid - ρbubble )

3. System interaction..
The mass of fluid in the sense line and the compressibility of the bubble have a natural frequency just like any spring-mass system does.
Heaven help you if it's anywhere near that of a control system using the signal.

Get the air out.

old jim
 
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FAQ: Effect of Air Bubble on Differential Pressure Measurement

1. How do air bubbles affect differential pressure measurement?

Air bubbles can cause inaccuracies in differential pressure measurement by altering the pressure exerted on the sensing element. This can lead to false readings and affect the overall measurement accuracy.

2. What causes air bubbles to form in the system?

Air bubbles can form in the system due to a variety of reasons, such as improper installation, leaks in the system, or entrained air in the fluid being measured. They can also be caused by changes in temperature or pressure within the system.

3. What are the potential consequences of air bubbles in differential pressure measurement?

Air bubbles can lead to measurement errors and affect the reliability and repeatability of the measurement. They can also cause damage to the equipment and result in costly repairs or replacements.

4. How can air bubbles be prevented in differential pressure measurement?

To prevent air bubbles, it is important to ensure proper installation and maintenance of the equipment. This includes checking for leaks, purging the system of air before use, and using appropriate equipment for the specific application.

5. Can air bubbles be accounted for in differential pressure measurement?

While it is not possible to completely eliminate the presence of air bubbles, certain techniques such as averaging multiple readings and using advanced algorithms can help to compensate for their effects on the measurement. However, prevention is always the best approach to ensure accurate and reliable differential pressure measurement.

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