22
Calibration
Introduction to Calibration
In technical language,
calibration
is referred to the process used to determine accuracy. It is the
comparison of a measuring instrument against a standard to establish the possible errors in a specific
range.
Calibration is of such importance that the United States Government created an agency called the
National Institute of Standards and Technology (NIST) that is tasked to maintain standards for values of
SI units and industrial standards, calibration has become a helpful tool in providing the traceability of
their subjects of study by adhering to the basic standards of calibration.
All Zaxis calibrations are
traceable to standards set by the NIST.
The Isaac can use up to ten calibration points throughout the range of the sensor to correct the linearity
of the sensor output. All ten points are dynamic, meaning they can be adjusted to match where the user
needs the best accuracy across the range.
In the calibration mode the pneumatic assembly will open to bring pressure, vacuum, or flow to the test
port. The sensors will also be active to show the current reading. With a pressure or flow standard
attached to the test port the machine is taught the values from the standard. Calibration points have
been selected across the range at the factory the greatest accuracy.
Two procedures will be outlined, Calibration Verification and Calibration Modification. All Isaac models are
initially calibrated at our facility. The verification procedure should be the most commonly used. If the
calibration needs to be modified then use the modification procedure.
Calibration is always to be performed in units of psig.
Important: Calibration of this instrument is for the sensor only (not a
leak calibration) and is factory set. Leak standards can be obtained
from Zaxis Inc. and can be used as a transfer standard to establish
applicable leak rates. All standards should have at least three tiers of
uncertainty. i.e. Isaac has a tolerance of .25% FS (full scale) therefore
pressure standards should be at least equal to or less than .1% FS.
