Fluctuations in pressure gauge calibrations? 3

[ipocoyo]

Hello All,

Another observation that I am rather curious about. Is there a reason why pressure gauges in particular tend to have fluctuated readings between calibrations? For example, the first calibration would have readings of 0,30, and 60 Pa. The next year it would be 0, 32, and 62 Pa. The next successive calibration would show 0, 30, and 54 Pa.

Also, is there a particular reason why pressure gauges tend to drift more at higher pressures? For example, I have a differential pressure gauge (0-60Pa) which seems to have have an accuracy of 0% at test points 0 and 30Pa. However, when testing at 60Pa (max range) the needle seems to be showing at 55 Pa instead of 60Pa. I've noticed this trend happening with a few other gauges as well.

Still an intern

 

[IRstuff]

What are its specifications? On what range were the readings made? Is it stable during normal use? Was it abused?

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[thebard3]

It's why you need a pressure transmitter if you want high accuracy and repeatability.

Brad Waybright

It's all okay as long as it's okay.

 

[danw2]

I assume the units are kPa, not pa, correct?

What is the maximum range/number on the gauge dial? 100 Kpa?

Is there a zero adjustment screw on it somewhere?

Are it a liquid filled gauge?

 

[Compositepro]

Is it standard practice to tap pressure gauges during calibration checks?

 

[thebard3]

Is it standard practice to tap pressure gauges during calibration checks?

That depends.

-OR-

Brad Waybright

It's all okay as long as it's okay.

 

[danw2]

Is it standard practice to tap pressure gauges during calibration checks?

Yes, tapping the case is standard practice.

ASME B40.100-2005 Pressure Gauges and Gauge Attachments, in Section 6.2.4 Procedures allows tapping the gauge case lightly as part of the defined tests for accuracy, repeatability and hysteresis.

 

[ipocoyo]

Hi All,

Sorry, I should have specified! The gauge itself is a room differential pressure gauge.The instrument itself has an accuracy of 0% at test points 0 and 30 Pa. However, it seems to be out of tolerance by 5Pa at its maximum pressure of 60 Pa. The differential room pressure never exceeds 20Pa and the gauge itself is only about 5 years old. Sorry for the confusion.

Still an intern

 

[thebard3]

Accuracy of zero percent? Your instrument will never pass calibration.


Brad Waybright

It's all okay as long as it's okay.