Crystal WT Series Panel Mount Digital Pressure Gauge - Manual (Page 18)

Support  16
XP2i Operation Manual
—
CALIBRATION
Factory Adjustment
If adjustment is re quired, we recommend re turn ing the unit to the factory. Factory service off ers benefi ts you won’t fi nd anywhere else. We have the facilities
to test your gauge at a variety of temperatures utilizing NIST traceable stan dards in our A2LA accredited laboratory, resulting in calibration certifi cates that
provide performance data over temperature. Furthermore, upgrades may be available to add or en hance operating features. We designed the product to last,
and we support it so that you can get the most from your in vest ment.
Calibration Frequency
Under normal operating conditions, we recommend the XP2i be calibrated on an annual basis. Your quality system may require more or less frequent calibra-
tion, or your experience with the gauge, or operating environment may suggest longer or shorter intervals.
Although we prefer that you return the XP2i to Crystal En gi neer ing for calibration, ordinary re cer ti fi ca tion and/or ad just ments may be performed by any
qualifi ed personnel with appropriate training and equipment.
Span Factor
There are no internal potentiometers. The XP2i contains a “span” factor, set to approximately 1 (as shipped from the factory). As com po nents age this may
need to be changed to a value slightly higher or lower, to slightly increase or decrease all readings. This adjustment can be made with or without a computer
(see Confi gXP Confi guration Software ).
 Span Factor adjustment
Note: The following in struc tions are ONLY intended for such qualifi ed personnel with appropriate test equipment. We recommend that the calibration stan-
dards used have a min i mum rated accuracy of 0.025% of reading, or equivalent in terms of percent of full scale. This level of accuracy requires the use
of piston (deadweight) gauges or very high performance pressure controllers.
“Zero” the XP2i, then record displayed pressure for two or more pressure points. De ter mine if the XP2i would benefi t from an overall increase or decrease of
the indicated pressures.
To change the span factor from the keypad, turn off the XP2i, then press the
(
on/off
)
,
(
units
)
, and
(
peak
)
buttons si mul ta neous ly. The fi rmware version will
be briefl y displayed, followed by the word cal , followed by the actual span value. The span factor may be adjusted by pressing either the
(
units
)
or
(
peak
)
button to increase or decrease the value, respectively. The value changes in 0.0001 increments. Press the
(
zero
)
button to store the new value in memory, or
the
(
on/off
)
button to cancel the change.
For absolute XP2is, it is possible to correct for long term drift using a second calibration factor, zero value off set. Confi gXP and a barometric reference with ac-
curacy of 0.1 PSI or better is required to perform the calibration. To calibrate the zero off set, clear the zero as described earlier in this manual by pressing and
holding the
(
zero
)
button until (
) appears. Once cleared, subtract the displayed pressure from barometric pressure, add this diff erence to any existing
zero value off set in Confi gXP, and update the gauge (new value = barometric – displayed + existing). For example, if the displayed value is 14.5 PSI, barometric
pressure is 14.7 PSI, and the existing zero value off set in Confi gXP is 0.1 PSI, the new zero value off set would be 0.3 PSI (14.7 - 14.5 + 0.1 = 0.3).
The span factor and zero value off set can be viewed and set directly by Confi gXP. Span factor adjustment through the keypad
can be disabled by Confi gXP through the disable span factor feature or by password protecting the XP2i .
XP