Re: how to calibrate the gauge ?
I'm from aerospace sector: I see calibration as the initial action whereby it "sets the baseline" for a piece of equipment (typically) against a known standard in controlled conditions - in a certified laboratory or other certified facility. This is the most formal method. It can then be used with confidence for all future verifications (measurements), usually in uncontrolled conditions, until an established schedule would require it to be calibrated again (under a periodic recalibration schedule). This cycle repeats for the life of the piece of equipment. Again, this is all quite formal.
If you are talking about simply verifying the same piece of equipment at time of use, this may be to check that basic functions are in working order. Checking for any obvious defects which might indicate possible malfunction. This might even entail testing the gauge over a range of values and compare the results to a known/expected value. This is similar to "calibration", but perhaps could be argued that it is not quite as formal. It would depend on what your quality system allows, what the gauge is used for, whether personnel are trained, what your customer requires from you and such...
~hope this helps a bit~
Last edited by Mike_H; 11th July 2009 at 02:00 AM.