PN: 2975 Rev F, 3/2004
Page 16 of 24
PRESSURE is Our BUSINESS
™
The XP2 uses RTS/CTS hardware flow control, but only the CTS line is used; since the XP2
only produces output when requested to do so, this is unlikely to cause a problem.
Data transmitted from the XP2 will always be 7-bit ASCII. Any high-ASCII characters indicate
a line-noise problem, or a problem with the XP2 or PC.
The XP2 has very thorough integrity checks to catch corruption of program or calibration
data memory. Should the data memory integrity check fail, the unit displays “ERR 1” on
the display as the value line of the serial output. It is important to check for this, or you may
mis-parse that line as “1 PSI”, depending on your program. Should the program memory
integrity check fail, the unit will continuously reset, blinking the LCD on and off, and the serial
output will alternate between the bootloader signature and a line reading “CRC FAIL”.
This condition can be recovered from, in the field, by reloading the unit’s firmware; contact
technical support for details.
Calibration
If adjustment is required, we recommend returning the unit to the factory. Factory service
offers benefits you won’t find anywhere else. We have the facilities to test your gauge at a
variety of temperatures utilizing NIST traceable standards, resulting in calibration certificates
that provide performance data over temperature. Furthermore, upgrades may be available
to add or enhance operating features. We designed the product to last, and we support it so
that you can get the most from your investment.
Under normal operating conditions, we recommend the XP2 be calibrated on an annual
basis. Your quality system may require more or less frequent calibration, or your experience
with the gauge, or operating environment may suggest longer or shorter intervals.
Although we prefer that you return the XP2 to Crystal Engineering for calibration, ordinary
recertification and/or adjustments may be performed by any qualified personnel with
appropriate training and equipment. The following instructions are ONLY intended
for such qualified personnel with appropriate test equipment. We recommend that
the calibration standards used have a minimum 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, such as those
manufactured by DH Instruments (www.dhinstruments.com).
There are no internal potentiometers. The XP2 contains a “span” factor: “Userspan”, set to
approximately 1 (as shipped from the factory). As components 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: WinXP2 Configuration Software).
“Zero” the XP2, then record displayed pressure for two or more pressure points. Determine if
the XP2 would benefit from an overall increase or decrease of the indicated pressures.
To change the userspan factor from the keypad, turn off the XP2, then press the (on/
off),
and
buttons simultaneously. The firmware version will be briefly
displayed, followed by the word “cal”, followed by the actual userspan value. The userspan
factor may be adjusted by pressing either the
or
button to increase or
decrease the value, respectively. The value changes in 0.0001 increments. Press the
button to store the new value in memory, or the (on/off) button to cancel the change.
Note: Changing the userspan value causes the XP2 to reset. After the reset, the XP2 will
have to be re-zeroed. Remove any applied pressure and zero the gauge. Then check to see
if the adjustment was correct and achieved the desired effect.
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