Test Gauge Failure
Test Gauge Failure
(OP)
Hi All,
An Ashcroft test gauge model#1082(pressure range 0-1500 PSI) with a 0.25% accuracy FSO was set up for calibration on an Ametek DWT having an accuracy of 0.1% of nominal value and was found to be within 0.25% tolerance, tested okay.
However, same(gauge) was sent to a third party for certification and they had used a DWT having an accuracy of 0.015% of reading .When they performed an as found verification they indicated to me that the gauge was out of tolerance and failed calibration.
Test equipment used with a lower accuracy for calibration will show a significant difference in results but if same instrument(gauge) was calibrated with a 0.1% and passed, are we going to consider the gauge failed if used with a 0.015 % test equipment?
Thanks and appreciate your feedback.
An Ashcroft test gauge model#1082(pressure range 0-1500 PSI) with a 0.25% accuracy FSO was set up for calibration on an Ametek DWT having an accuracy of 0.1% of nominal value and was found to be within 0.25% tolerance, tested okay.
However, same(gauge) was sent to a third party for certification and they had used a DWT having an accuracy of 0.015% of reading .When they performed an as found verification they indicated to me that the gauge was out of tolerance and failed calibration.
Test equipment used with a lower accuracy for calibration will show a significant difference in results but if same instrument(gauge) was calibrated with a 0.1% and passed, are we going to consider the gauge failed if used with a 0.015 % test equipment?
Thanks and appreciate your feedback.





RE: Test Gauge Failure
The most common mistake in using a DWT is failing to manually rotate the weights to remove seal friction from the piston packing gland. That's why the weights are supplied as round plates that stack and nest neatly.
Without spilling the beans about that secret, ask for a copy of their test procedure.
Mike Halloran
Pembroke Pines, FL, USA
RE: Test Gauge Failure
xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Test Gauge Failure
I'm curious how the calculations were made. Is the instrument very close to its uncertainty limit?
TTFN
I can do absolutely anything. I'm an expert!
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers
RE: Test Gauge Failure
The results are as follows;
When I tested the same gauge using a 0.05 % accuracy digital test gauge;
Input(PSI) Actual(PSI)
0 0
300 300.25
600 600.32
900 900.41
1200 1200.57
1500 1500.63
All readings were found to be within +/- 0.75 FSO.
Third Party results;
Input(PSI) Actual(PSI)
0 0
300 299.09
600 599.11
900 899.23
1200 1199.42
1500 1499.51
Since they had used a lower accuracy (0.015%),based on their results above, why is the gauge considered failed if found acceptable using a 0.05% test gauge for verification?
Appreciate the feedback.
RE: Test Gauge Failure
xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Test Gauge Failure
My quick look suggests that the random error is VERY small. The only anomaly is the 0 psi reading from the 3rd party, which, based on scale and offset, should have been closer to -1 psi, which would still have been well within the requirement.
A true "calibration" would measure the scale and offset errors, which are then applied to the resultant data and the residual error is the uncalibratable error.
TTFN
I can do absolutely anything. I'm an expert!
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers
RE: Test Gauge Failure
Not sure why the text is munged.
TTFN
I can do absolutely anything. I'm an expert!
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers
RE: Test Gauge Failure
The 1082 is a bourdon tube gauge with a 270 deg dial scale.
It has either 5 psi or 2 psi minor divisions, depending on the dial diameter.
Getting a reading to the 2nd decimal place is truly an admirable task. Eagle eyes.
The gauge performance is even better than reported/expected using my desk calculator which shows 0.25% of 1500 to be almost 4 psi; 3.75 psi to be exact.
If it were me I'd be looking for another "3rd party" cal lab.
RE: Test Gauge Failure
Thanks for the feedback.