I'm having an argument regarding the appropriate definition of full scale, where a vacuum indication is present. This argument includes the determination and application of accuracies. The gauge indicates -15 mmHg to 500 PSI. The accuracy listed is ±0.1%FS for vacuum and ±0.04%Rdg + ±0.01%FS for pressure.
I'd guess 0.1% of 15mmHg is the full scale for vacuum and pressure (0.04% of rdg + 0.05) for pressure.
Just kind of a layman's guess, have not done PhysD in ages.
I was often told that you added them together. But in this case that would make for a huge accuracy so convert 500 PSI to mmhg 25857.52 then add 15 then it would be +/-25.8 but that cant be rights so I am guessing also of the 15 mmhg for the full scale. I usually call the manufacturer to confirm but anymore Wika, Ashcroft, and Fluke are getting hard to get ahold of. In that situation though it sounds like it specifically spells out what tolerance to use. Does +/-.15 mmhg make sense? Usually the vacuum side on those gauges are not very accurate.
This gauge is a Fluke 700RG series. Fluke indicates -15 PSI ( 30 mmHg ) to 500 PSI. Fluke lists different accuracies for vacuum and psi.
I was taught FS meant needle's complete movement. That includes -15 psi ( mmHg ) to 500 PSI. That would make the FS 515 PSI but the accuracies listed completes issues. I have called Fluke and I'm awaiting a return call.
Because of the bilateral tolerance I'm thinking the Bryan is right, Im interested in what Fluke says
Looking at Fluke's website I am guessing what you have is the model 700RG07 which has a range of -12 to 500 psi and a resolution of 0.01 psi.
The specs on the data sheet are as follows:
Positive pressure = ±0.04% of reading + 0.1% of range.
Vacuum = ±0.1% of range
Fluke has a calibration manual that covers this model.
http://media.fluke.com/documents/700g____cmeng0100.pdf
It appears that Fluke takes the simplified route and defines the range as 500 psi. (though the argument could be made that the range is actually 512 psi, but we will save that discussion for a later time.)
From Fluke's Calibration manual the test points and tolerances are as follows:
Input Lower Upper
pressure Limit Limit
500.00 500.25 499.75
400.00 400.21 399.79
300.00 300.17 299.83
200.00 200.13 199.87
100.00 100.09 99.91
0.00 0.05 -0.05
-6.00 -5.50 -6.50
-12.00 -11.50 -12.50
No, I didn't mess up the "upper" and "lower" limits. I just typed it straight out of Fluke's Calibration Manual. :-o
I have read Fluke's calibration manual and it is a bit confusing.
This confusion has caused a serious discussion. My opinion is full scale includes all "movement" involved. The service provider has determined that the vacuum and pressure specifications are separate and should be treated as such.
The sensor can behave differently to vacuum and pressure and so have a different tolerance for them. If we "take the simplified route" and just accept 500 psi as FS then @ 100psi the tolerance +/- 0.09psi (0.04%rdg + 0.01%fs) is correct.
If Fluke interprets FS as 500psi instead of 512psi they make the tolerance tighter and err on the side of caution, probably what they did here.
All comments are appreciated.
Semper Fi
Just my two cents, the movement may be to 515 but the stated spec only covers to 500, so 500 would be FS. I have not done Phys/Dem in years but I have seen movements before that were larger than the stated FS spec. I guess I see it as the FS spec of 500 is a warranted spec even though the range of the movement goes to 515 so 501-515 is not warranted.