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askaripour
Associate

Join Date: Jan 2010
Posts: 26

DPT Measuring Range Unit

01/20/2013 2:01 AM

Hi!

according to my experience, measuring range of a DPT (differential pressure transmitter) usually is expressed in unit of BarA or BarG (A refers to absolute and G refers to gauge). while i think in this case, purpose of measurement is measuring the DIFFERENCE between pressure of two point and using concept of absolute or gauge is irrational.

if any one can explain reason of using concept of absolute or gauge for measuring unit of DPT, it will be highly appreciated.

Best Regard!
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Iris
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Join Date: Jul 2010
Posts: 669
Good Answers: 176
#1

Re: DPT meaguring range unit

01/20/2013 9:18 AM

Technically, all pressure measurement is differential, where the differential is one pressure compared to a reference pressure.

Absolute measurement references absolute zero, so one side of a pressure measuring instrument 'sees' absolute zero, or as close as it can be manufactured.

Gauge measurement reference atmospheric pressure, so one side of the pressure measuring instrument 'sees' or is vented to atmospheric pressure.

Differential measurement references an applied pressure, whatever that might be, below or above atmostpheric pressure.

While it is convention to omit the letter G for gauge measurement, the other two, differential and absolute, should have their respective identifying letters as part of the engineering units. Units for differential pressure are correctly rendered as BarD or PSID, with the D for differential.

Calling a differential measurement 'absolute' or 'gauge' is, indeed, incorrect.
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Iris
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Join Date: Jul 2010
Posts: 669
Good Answers: 176
#2
In reply to #1

Re: DPT meaguring range unit

01/20/2013 10:03 AM

Let me amplify my last statement:

Calling a differential measurement 'absolute' when the reference side is not absolute zero is incorrect.

Calling a differential measurement 'gauge' when the reference side is not atmospheric pressure is incorrect.
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askaripour
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Join Date: Jan 2010
Posts: 26
#3
In reply to #1

Re: DPT meaguring range unit

01/21/2013 4:12 AM

Helpful!

Thank you
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