Crystal XP2i User manual

C R Y S T A L
engineering corporation
Operation Manual
XP2i
ATEX Digital Test Gauge

Contents
Introduction........................................................1
Operating Instructions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Unitsbutton.............................................................3
Zero...................................................................3
Peak detection and Average . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Resetting (clearing) recorded peak values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Automaticshut-off.......................................................4
Backlighting the Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
MeasuringVacuum......................................................5
Water Density (Inches of Water). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Overpressure Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Filter...................................................................6
Low battery indication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Battery replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Reset..................................................................7
Troubleshooting.....................................................7
Noisy or unstable reading when used with uids ..............................7
Non-repeatability of pressure measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Slow return to zero and/or non-repeatability of pressure measurements. . . . . . . . . . 8
Err1displayed..........................................................8
Err2displayed..........................................................8
Display continuously ashes all segments ...................................8
Digital Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
I/OSettings.............................................................9
Communication Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Query Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
MessageStore..........................................................9
Model................................................................10
Pressure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Pressure (one line). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Pressure,High..........................................................10
Pressure,Low..........................................................10
Range................................................................10
Return Average Pressure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Return the Average Window Size. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
SerialNumber .........................................................11
Version...............................................................11
WaterDensity..........................................................11
ZeroCheck............................................................11
Commands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
ClearPeaks...........................................................12
Disable/Enable Peak Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
MessageStore.........................................................12
Next Pressure Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
NoAutoOff............................................................12

Reset.................................................................12
Set the Average Window Size. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Streaming Data On/Off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
WaterDensity..........................................................13
Zero..................................................................13
Acknowledgment of a Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Troubleshooting the Digital Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Effects of Password Protection on Commands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Programming Tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Calibration........................................................16
XP2i Model & Serial Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Serial Numbering System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Model Numbering System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
Accuracy.............................................................19
Temperature...........................................................19
Humidity..............................................................19
Media Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
Pressure Conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Connection ...........................................................20
Power ................................................................20
Enclosure .............................................................21
Pressure Ranges, Display Scales & Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Intrinsic Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
ATEX .................................................................23
CSA..................................................................23
IECExScheme.........................................................23
Certifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
C-tick ................................................................23
Software..........................................................23
LabVIEW™ drivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
CongXP Conguration Software. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Replacement Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Accessories.......................................................24
ACadapterkit.........................................................24
Plastic Carrying Case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
6″Gauge Adapter Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
8½″Gauge Adapter Kit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
RS-232Cable..........................................................24
Trademarks........................................................24
European Community Declaration of Conformity . . . . . . . . . . . . . . . . . . . . . . . .25
Warranty..........................................................26
HowtoContactUs:.....................................................26

XP2i ATEX User’s Manual •Page 1
C R Y S T A L
engineering corporation
Introduction
Thank you for choosing the XP2iDigital Test Gauge from Crystal Engineering Corporation.
Your XP2iis a combination of leading edge technology and rugged industrial design.
Accuracy is 0.1 percent of reading - so any XP2ican typically replace several gauges you may
have been using. The XP2iis fully temperature compensated - so there is no change in accu-
racy throughout the entire operating temperature range!
The case, and almost all metal components, are stainless steel. Gaskets seal out dust and water.
Even the RS-232 connector (with or without the cover) is fully sealed. Circuitry is mounted in a
shock absorbing elastomer, and the batteries are easily accessible by removing two screws. But
you won’t need to change batteries often, since 3 AA batteries operate the XP2ifor up to 1500
hours of continuous use. If you are mounting the gauge in a permanent location consider order-
ing the external power supply kit (PN: 2984). With the external power supply the batteries serve as
an automatic backup supply, in case of power failure. Other features include:
•continuous recording of peak and valley pressure readings
•a removable lter (to keep out large particle contaminants)
•all welded 316 stainless steel sensor
•can be cleaned for oxygen service
Your XP2ican be customized, through the use of CongXP™ software available from Crystal Engi-
neering. Your personal computer can disable, enable or modify a variety of features of your XP2i.
Look for the
ConFIGXP PROGRAMMABLE
logo for programmable features, like:
•a user dened pressure scale, and/or disable unused pressure units
•password protection to prevent unauthorized changes
•disable keypad recalibration, peak button, and/or units button
•expand or decrease allowable Zero range
•set the gauge to a dierent density of water factor (4°C, 60°F or 68°F)
•store a 12 digit ID or tag number in non-volatile memory
•adjust calibration values
We hope your XP2i meets your expectations, and we're interested in any comments or suggestions you
may have. You can send us a note at: [e-mail] features in this and
our other products are a direct result of your comments!
Crystal Engineering is the company that designs, manufactures, markets and services the XP2i, 30
series pressure calibrators, MultiCal multimeter pressure adapters and a variety of industry spe-
cic pressure measuring equipment. Crystal Engineering pioneered features like full temperature
compensation and “of reading”rated gauges and calibrators. Pressure measuring equipment is the
only thing we do and that’s why we say: PRESSURE is Our BUSINESS™

Page 2 •XP2iATEX User’s Manual
C R Y S T A L
engineering corporation
Operating Instructions
The XP2iis shipped with batteries installed, so it’s ready to use. Press and hold the
(on/off)button. The XP2iwill rst test all LCD segments. Release the but-
ton when the XP2iindicates pressure.
The XP2ialways resumes operation in the mode and the units of the pressure last used, and it
does not automatically rezero when turned on.
Connect the XP2ito your system. Use pipe thread tape or pipe thread sealant on the ¼″NPT t-
ting. Always use a wrench (¾″or 19mm) for installation and removal of XP2i !There is a limit to
how much rotational force can be applied to the case, so don’t rely on, or use, the case to screw the
XP2i into a tting, and don’t use the case to remove the XP2i tting, either.
WARNING: Severe injury or damage can occur through improper use of pressure instru-
ments! Do not exceed recommended pressure limits of tubing and ttings. Be certain all pres-
sure connections are secured.
CAUTION: Never insert any object (other than the ⁄” NPT metal lter) into the pressure
connection! The sensor diaphragm is very thin and can be damaged or destroyed by solid or
sharp objects. Cleaning of the sensor must be done with appropriate solvents only.
Most XP2is are intended for gauge pressure measurement. That is, they indicate the dierence
between applied pressure and ambient barometric pressure. However, the
zero
button can be
used to force an XP2ito read zero pressure at any applied pressure, up to the full scale rating of
the gauge. The factory default setting limits the maximum zero value to 200 PSI, but this limit can
be changed with
ConFIGXP
.
Some XP2is are rated for absolute pressure. Absolute gauges indicate the dierence between
applied pressure and an internal vacuum reference. Absolute pressure is always positive. For
instance barometric pressure at sea level is on average about 14.7 PSI (approximately 100 kPA or
1 Bar), so at sea level this is the lowest expected pressure indication. However, absolute gauges
can be “zeroed”(unless prevented by CongXP). After zeroing an absolute gauge it is possible to
indicate a negative pressure.
WARNING: This gauge can display zero pressure when connected to a source of pressure! Do
not rely on the display indication before disconnecting - it may not be indicating true pres-
sure. Never disconnect pressure instrumentation without rst relieving system pressure!

XP2i ATEX User’s Manual •Page 3
C R Y S T A L
engineering corporation
Units button
Pressing this button causes the XP2ito select the next available unit of pressure
measurement. See “Pressure Ranges, Display Scales & Resolution” for the list of
pressure units available for your model.
ConFIGXP PROGRAMMABLE
Units that you don’t need or never use can be
turned o. You can also dene a special unit for your XP2i with CongXP. That way you can use the
XP2i to display directly in a unit not otherwise available, such as feet of seawater, or foot-pounds
of torque. When your custom unit is selected and displayed on the XP2i, all pressure unit icons will
be o.
Zero
To zero the XP2i , you must turn o peak indication, then press the
zero
button
for at least ½ second. The display will then briey ash all dashed lines (- - - - -),
indicating that it has been re-zeroed. If you attempt to zero the gauge while more
than 200 PSI is applied (or the pressure limit set with CongXP), the command will
be ignored, and “- -HI-” will be displayed.
WARNING: This gauge can display zero pressure when connected to a source of pressure! Do
not rely on the display indication before disconnecting - it may not be indicating true pres-
sure. Never disconnect pressure instrumentation without rst relieving system pressure!
You can clear the zero value: Turn o peak indication then press and hold the
zero
button until
the display changes from (- - - - -) to (- - -). This is especially useful for absolute gauges that have
been zeroed while measuring barometric pressure.
Zeroed Clear Zero (Unzero)
ConFIGXP PROGRAMMABLE
You can change the point at which the Zero button will display
“- -HI-”. For instance, you could set the maximum zero to 3000 PSI, if you need to mix high pres-
sure gases. You can also disable the zero button entirely, by setting the Zero value to a large nega-
tive number.
The
zero
button changes its function when the peak high (
HI
) or the peak low (
LO
) icon is
displayed. While a peak icon is displayed the
zero
button becomes the
clear
button.
PSI inH2O inHg kpa
mmHg mmH2O mbar kgf/cm2
LO
HI
PSI inH2O inHg kpa
mmHg mmH2O mbar kgf/cm2
LO
HI

Page 4 •XP2iATEX User’s Manual
C R Y S T A L
engineering corporation
Peak detection and Average
Pressing the Peak button causes the display to cycle through the following:
HI
. . . . . . . . . . Recorded maximum pressure
LO
. . . . . . . . . . Minimum recorded pressure
HI
LO
. . . . Average pressure*
<No Icon> . . . . Live pressure display
Peak high and low values are not saved when the gauge shuts o; they will reset to the current
reading when the XP2iis turned on or reset.
* From the factory this Average Pressure is disabled. Use CongXP to enable.
ConFIGXP PROGRAMMABLE
In some cases the ability to display a peak value may not be
needed, or may even be dangerous. CongXP allows you to disable this button.
XP2is can average 1 to 10 readings, recalculated every time pressure is measured (3 times per
second). Enable and set the number of readings to be averaged with CongXP.
Resetting (clearing) recorded peak values
Peak values can only be cleared when displaying either a high or low recorded
pressure. Press the
clear
button for at least ½ second. Dashed lines will then
briey appear across the display and both
HI
and
LO
icons will ash briey,
indicating that both peak values have been cleared. Both peak high and low values
will then display the current applied pressure. Pressing the
clear
button while either peak hi or
peak lo icon is displayed will not aect the zero value. If you need to rezero the gauge, you must
turn o both peak icons by pressing the
peak
button.
Automatic shut-off
The XP2ihas a shuto timer and will turn o automatically after 20 minutes of operation. Pressing
any button or sending any command via the RS-232 connection resets the shuto timer for an-
other 20 minutes of operation.
The shuto feature can be defeated, if desired, when turning the XP2ion. Pressing the
(on/off) and
zero
buttons simultaneously will prevent the XP2ifrom automatically turning o.
The XP2iwill briey display the words “No Auto O” to indicate that it will not turn o.
This procedure is required each time the XP2iis turned on, if you want to defeat the auto-shuto.

XP2i ATEX User’s Manual •Page 5
C R Y S T A L
engineering corporation
Backlighting the Display
Pressing the (backlight) button instantly lights the display at maximum brightness,
but to keep it on you need to hold down the button for 2 seconds. The display will ash
briey, indicating that it will stay on for 1 minute. If you press the button again, the
backlight will go into a lower brightness setting to extend battery life, the display will again ash
briey, and remain on for 2 minutes. Press the button once more and the light will go out.
If you start the XP2iin the“No Auto O” mode, you select the brightness level the same way, but
the light will never time out and turn o; you will have to either turn o the XP2ior press the
backlight again until the light goes out.
Measuring Vacuum
All versions of the XP2ican be used to measure moderate vacuum, though only ranges of 300 PSI
(and 20 bar or 2000 kPa) and lower are actually tested and certied for vacuum operation.
When measuring pressure less than ambient barometric conditions, a minus (-) sign will appear.
XP2is are not recommended for continuous use at high vacuum.
Absolute gauges (models with a “B” in front of “XP2I” in the part number) will NOT indicate a
negative sign when vacuum is applied, unless the zero button has been pressed while a pressure
greater than full vacuum is applied to the gauge. If your absolute gauge does indicate a nega-
tive pressure, you can clear the zero value (“unzero”) by pressing the zero button until the display
changes from ----- (5 dashes) to - - - (dash, space, dash, space, dash). See “Zero” for details.
Water Density (Inches of Water)
The following applies only to models where inches of water are available. As shipped from the
factory, the XP2iis set to display inches of water corresponding to the density of water at 4°C
(39.2°F). You may require a dierent water density for your application, so the XP2ican be set to
use the density of water at 20°C (68°F) or 15.6°C (60°F), instead.
To check and or change the water density setting from the keypad, turn on the XP2iby pressing
the (on/off) button and the
units
button simultaneously. The display will indicate either
“4C” or “60F” or “68F”.
Press the
units
button until the display cycles to the desired water density, then press the
zero
button to store the selection (this will not zero the gauge).
ConFIGXP PROGRAMMABLE
Select and set the desired density of water. If the XP2iis pass-
word protected, you will not be able to view or change the water density from the keypad.

Page 6 •XP2iATEX User’s Manual
C R Y S T A L
engineering corporation
Overpressure Conditions
The XP2iwill read pressure up to approximately 110% of the rated pressure range. Above 110%
percent of the range the display will start ashing and the readings will not be reliable. The zero
function does not aect the point at which the display starts ashing to indicate overpressure,
so depending on the zero value it is possible that the display can start ashing without the maxi-
mum pressure being displayed.
For instance, if a 100 PSI XP2iis zeroed when 30 PSI is being applied, it will indicate that the over-
pressure condition has been reached at 80 PSI (i.e., 110% x 100 PSI – 30 PSI = 80 PSI).
Overpressure can aect accuracy, but the eect is only temporary unless the sensor has been
destroyed. See Specications for maximum overpressure.
Filter
The XP2ihas a removable, stainless steel mesh lter, installed in the bottom of the pressure con-
nection. This lter is designed to keep large particles from becoming entrapped in the sensor
cavity.
If the XP2ifails to return to zero, or returns to zero or new applied pres-
sures slowly, the lter may be obstructed. The lter can be removed and
cleaned if necessary, by unscrewing it with a 5⁄32”(4 mm) hex key, and
using solvents and/or compressed air to clean it out. Or, you can pur-
chase a replacement lter, PN:3002.
Low battery indication
The battery icon ( ) is the rst indication of a low battery. The
XP2iwill continue to operate accurately while the icon is visible.
When the batteries are exhausted, the letters“batt” will appear
across the display. After“batt” appears, no pressure measurements
will be possible until the batteries are replaced.
Battery replacement
The XP2iuses 3 AA batteries*. Batteries must only be changed in a non-hazardous area! With the
hex key wrench (5⁄64”[2mm], provided with the gauge), unscrew the two rear panel screws to gain
access to the battery compartment. After replacing the batteries, the XP2iwill start operating
immediately (without having to press the button). This indicates that a complete reset has oc-
curred, and is normal.

XP2i ATEX User’s Manual •Page 7
C R Y S T A L
engineering corporation
WARNING: The XP2i is Intrinsically Safe only if powered by one of the following battery
types: Rayovac Maximum Plus, Energizer® E91, Energizer® EN91, or Duracell MN1500.
Reset
If for some reason the XP2ineeds to be reset,
remove any battery for at least one minute, then
reinstall the battery. If the reset is successful, the
XP2iwill start operating without pressing the
(on/off) button. Reset will clear the zero, peak
values will be reset to the current reading, and the
XP2iwill be set to the default engineering units.
Troubleshooting
The XP2iis a very high performance gauge. Due to the high resolution of this product, you may
observe conditions that appear to be defects in the product, but are in fact a result of being able
to resolve and measure pressure to a degree not possible with other instruments.
Noisy or unstable reading when used with uids
When calibrating or comparing the indicated pressure from an XP2iagainst a hydraulic dead-
weight tester or piston gauge, the reading on the XP2imay appear unstable - the least signicant
digit jumps up and down several counts.
Reason: Gas (usually air) is trapped in the line between the gauge and the deadweight tester.
What is actually happening is the mass is oscillating up and down, and the combination
of gas and uid is acting like a spring. At higher pressures (above 2000 PSI, typically) this
may eventually diminish, as the gas dissolves into the uid.
Solution: Evacuate all tubing with a vacuum pump, before introducing uid into the system.

Page 8 •XP2iATEX User’s Manual
C R Y S T A L
engineering corporation
Non-repeatability of pressure measurements
When checking the gauge against a hydraulic deadweight, increasing pressure measurements do
not match decreasing pressure measurements.
Reason: As in the previous note, gas has dissolved into the hydraulic uid. When decreasing the
pressure, the dissolved gas then leaves the uid, but at an uneven rate, so small pressure
dierential (due to uid head pressure) may exist between the reference deadweight
and the gauge being tested.
Solution: Evacuate all tubing with a vacuum pump, before introducing uid into the system.
Slow return to zero and/or non-repeatability of pressure measurements
Reason: Filter is obstructed.
Solution: Clean lter - see “Filter”section for instructions.
Err 1 displayed
Reason: The XP2ichecks the integrity of internal calibration coecients every time it’s turned
on. If any coecients have been corrupted in any way, “Err 1” is displayed.
Solution: Contact factory for instructions on how to restore the memory to the original factory
settings.
Err 2 displayed
Reason: The XP2ihas tried to display a number too large for the display (i.e., more than 5 digits).
May be due to an electrical malfunction or numerical error.
Solution: Contact factory for further instructions.
Display continuously ashes all segments
Reason: After a reset, and after replacing batteries, the XP2ichecks the integrity of program
memory. If for some reason it has been modied or corrupted, it ashes all segments,
and prevents normal operation.
Solution: Contact factory for instructions on how to restore the memory to the original factory
settings.
Digital Interface
The XP2ican be connected to a personal computer via RS-232, using an ordinary DB9 exten-
sion cable (male DB9 for the XP2iconnection, female DB9 for the PC side). The interface lets you
record displayed readings and recorded peaks. The data string always includes the pressure units.

XP2i ATEX User’s Manual •Page 9
C R Y S T A L
engineering corporation
And the XP2ican be operated remotely, as if you were pressing the buttons. You can use a simple
terminal program to send the commands, or, you can incorporate them into your own software
program.
A special command, Streaming Data, initiates data transmission of displayed pressure at the rate
of approximately 3 times per second.
I/O Settings
The serial interface settings are:
BAUD RATE PARITY DATA BITS STOP BITS FLOW CONTROL
9600 NONE 8 1 NONE
Communication Format
Input is case-sensitive; all instructions should be sent in UPPERCASE. Instructions must be termi-
nated with a single carriage return (CR) character followed by an optional linefeed (LF) character.
Note that while the XP2iexpects either CR or CR/LF as command termination on its input, it
always appends a CR/LF pair to its output. For reference, CR is ASCII value 13 decimal, while LF is
ASCII character 10 decimal.
You have 30 seconds to complete an instruction. After 30 seconds, the XP2iwill evaluate whatever
it has received and try to match it to its table of commands. Since the command is incomplete, it
will fail to match and the XP2iwill return: N,Ø. (Negative acknowledgment with no reception er-
rors, so syntax is wrong.)
Query Instructions
All queries start with a question mark (?). Any pressure values returned are split across two lines;
the rst contains a oating-point value, and the second contains the name of the measurement
unit. Each line is right-justied in a xed width 10 character eld. (Since each line is terminated
with a CR-LF pair, this means the total length of the response to a measurement query is 24
bytes.) A decimal point will always be included with the pressure value (for clarity) even if it is not
displayed on the XP2i. For example, a pressure query of a 300 PSI XP2ion the mbar scale could
return a reading like this:
2478.
mbar
If the batteries are low enough to trip the low battery message, then any pressure query will re-
place the pressure value with the letters “BATT”.
Message Store
?MSG Retrieve the data (usually tag# or ID) from the message store.

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Model
?MOD Return the model name, up to 20 characters long. For example, an ATEX 100 PSI XP2i,
would return the following:
AX100PSIXP2I
Pressure
?P,U Pressure returns the pressure value, followed by the pressure unit on the second line.
Example:
-7.89
mmH2O
Pressure (one line)
?PRE Returns data and units on one line, and separates the reading and units with a comma.
Example:
2.01,PSI
Pressure, High
?P,H Pressure, High returns the stored peak pressure value, in whatever pressure units are cur-
rently being displayed.
91.3
mmH2O
Pressure, Low
?P,L Pressure, Low returns the peak low, or “valley” measurement, in the pressure units currently
being displayed.
-10.7
mmH2O
Range
?RNG Range, returns the pressure range of the gauge. It is returned in two, 10 character lines. The
rst line is the value, the second line is the engineering unit. For example, a 100 PSI XP2i
would return
100.00
PSI

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Return Average Pressure
?P,A Using the same format as the“?P,U” command, the average pressure is returned. If averaging
is disabled, “X,0”is returned. Enable averaging through Cong XP.
Return the Average Window Size
?AVS The average sample size is returned. If averaging is disabled,“X,0” is returned. Enable averag-
ing through Cong XP.
Serial Number
?SN# The serial number is returned in two strings. A typical example is shown below:
3
12659
Version
?VER Version returns the XP2i’s rmware version as a 4 digit number preceded by the letter“R”.
This number is for factory use, only.
Example Version Number:
R0101
Water Density
?H2O Applies only to models with that include inches of water. Water density returns the current
density of water in terms of temperature with one of three values possible:
_4C
60F
68F
Zero Check
?Z,U Zero Check reveals how much was subtracted from the reading to zero the gauge, in the
pressure units currently being displayed. When batteries are installed or the XP2iis reset, the
zero is cleared, and equals zero.
32.7
kPa

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Commands
The following are commands. All commands start with an exclamation mark (!).
Clear Peaks
!CLR Clear high and peak low values by setting them to the current live reading (which might not
be zero). For instance, if the current live reading were 253 PSI, then both high and low peak
registers would contain 253.
Disable/Enable Peak Display
ConFIGXP PROGRAMMABLE
Prevent peak pressure readings from being displayed.
!NPK Prevents peaks from being displayed.
!PKS Enables peak button operation (default).
Message Store
ConFIGXP PROGRAMMABLE
!MSGx Up to 12 characters (usually tag# or ID) can be stored in EEPROM. Set the message with
“!MSGx”where “x” is the message.
Next Pressure Unit
!I,P This command is acknowledged with a simple “A,Ø”. To check which units were selected,
send the command “?P,U” to return the pressure value and the current pressure units.
No Auto Off
!NAO Prevents automatic shutdown. Every time an XP2iis turned on, it defaults to a shutdown
schedule of 20 minutes after the last button push or the last RS-232 command. This com-
mand will return:
NO
AUTO
OFF
To re-enable automatic shutdown, send the reset (“!RST”) command. (Read the Reset sec-
tion rst to be sure you understand all eects of performing a reset.)
Reset
!RST This command schedules a reset. There will be a three second pause before the XP2iresets;
during this time, no commands or queries should be sent to the unit. When the unit resets, a
product identication string, called the Boot Signature, is sent. (See the Programming Tips
section for more information.) Some communications noise, including a serial framing error,
is possible on reset. Resetting the XP2iclears the zero value, clears the peak high and peak

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low values, enables automatic shutdown after 20 minutes of inactivity (resetting that timer
to 20 minutes on reset), and selects the rst pressure unit on the XP2i(which can vary with
product type, but will be consistent for each reset operation). After a reset, you should query
and/or select appropriate measurement units using the“?P,U” and “!I,P” commands. If
the reset command fails to operate properly, or appears to “lock up” the device, contact tech-
nical support.
Set the Average Window Size
ConFIGXP PROGRAMMABLE
!AVS x Sets the number of pressure reading to be averaged. The valid rang is from 1 through 10,
i.e. !AVS 5<CR> or !AVS 10<CR>. If an invalid size is entered, or averaging is disabled, “X,0” is
returned. Averaging is enabled with CongXP, only.
Streaming Data On/Off
!SP1 Displayed pressure is sent out the serial port after each new reading, at a rate of approxi-
mately 3 readings per second. Returns data in the same format as the ?PRE query.
!SP0 Cancels streaming data output.
Water Density
ConFIGXP PROGRAMMABLE
!_4C Set the density of water to 4°C (39.2°F)
!60F Set the density of water to 15.6°C (60°F)
!68F Set the density of water to 20°C (68°F)
Zero
!ZER Zeroes the pressure readings by setting a zero value equal to the current applied pressure.
The zero cannot be cancelled, but it can be reloaded by calling this command again. To
check the zero value, send the Zero Check command (“?Z,U”). If you want to disable the
zero after enabling it, send the reset (“!RST”) command. (Read the Reset section rst to be
sure you understand all eects of performing a reset.)
Acknowledgment of a Command
The XP2ialways returns some indication to let you know a command or query was received and
acted on. For queries, the return of the measurement data is the acknowledgment. For commands,
possible acknowledgments are “A”, “N” or “X”, followed by a comma then a single digit. The digit
indicates whether there were any reception errors. The combination is left justied.
AThe XP2iunderstood the command and acted on it.
NThe XP2idid not understand the command, due to either syntax or reception errors.
XThe command was understood, but is not implemented at this time.

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Following an “A”, “N” or “X”, the single digits mean the following:
ØThere were no reception errors.
2Buer overow.
4Framing error.
6There were both buer overow and framing errors.
Example acknowledgment:
A,Ø Understood the command and acted on it. No reception errors.
N,4 Could not understand the command because there was a framing error.
N,Ø Could not understand the command, even though it was received without errors, so syntax
must have been wrong.
Troubleshooting the Digital Interface
The following section gives possible reasons for various error codes.
N,Ø The “Ø” indicates there were no overrun or framing errors, so the command was properly
received. However, the “N” means the XP2icould not match it to any allowed command. This
means the syntax must have been wrong. The command is rejected and nothing is done.
Possible reasons:
Instruction sent without a comma between “P” and “U” of the “?P,U” query.
More than 30 seconds passed to nish a command.
Line termination is incorrect; send carriage returns (CR) only, do not send line feeds (LF).
N,2 XP2ibuer overow, no action. In an overrun, bytes are lost, consequently the XP2iwill not be
able to match the command string. If it can’t nd a match, it returns “N”.
Possible reasons:
Not enough time allowed between commands. Check the communication parameters.
N,4 Framing error: Bytes were lost. Therefore, the command could not be matched. A framing er-
ror can sometimes occur after power-on, after reset, or when the batteries are changed; see
the Programming Tips section for suggestions on handling this.
Possible reasons:
Noise on the line either created a false start bit or obscured the stop bit.
Multiple, but infrequent, framing errors are probably due to noise on the connection.
Frequent framing errors likely mean the XP2ior the PC is not operating at precisely 9600 Baud.
Occasionally, plugging the RS-232 connection into the XP2iwill create a single framing error.

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N,6 Both buer overrun (N,2) and framing errors (N,2) occurred during this command. The “6”
represents the binary OR masking of the two bits used to indicate a buer overrun (bit 1)
and a framing error (bit 2).
Possible reasons:
Look at“Possible reasons” for troubleshooting the N,2 and N,4 error codes, above.
ERR 1 After sending a command or query, the XP2ireturns (and displays) “ERR 1”.
Reason:
The XP2ihas detected a CRC EEPROM error.
ERR 2 The XP2ireturns (and displays)“ERR 2”.
Possible reasons:
The XP2ihas tried to display a number too large for the display (i.e., more than 5 digits), or
may be due to an electrical malfunction or numerical error.
Effects of Password Protection on Commands
If the XP2i is password protected, the following commands will have no eect and return “X,O”:
!_4C, !60F, !68F, !NPK, !PKS, !MSG, !RAS, and !AVS.
Programming Tips
The XP2iis a very straightforward device to communicate with, provided you follow these tips.
This advice is derived from our own experiences automating systems based on the XP2i, as well as
the experiences of our users; following it will probably save you some time.
Anytime you establish (or re-establish) communications with the unit, you should use the
following initialization sequence, which will help you deal with possible noise due to reset, etc.:
1Reset the unit (unless you must preserve zero, peak values, etc.) by sending the“!RST”command.
2Wait 15 seconds.
3Read the Bootloader Signature, even if you ignore it, to clear it from the PC’s input buer; see
below for more details.
4Send a carriage return to clear any noise in the XP2i’s input buer.
5An error code, either “N,Ø” or “N,4” will be returned; this is normal (you have sent an empty
command); read it to clear it. The buers are now reset.
6Use the “?P,U” and “!I,P” commands to select the pressure unit you want to use.
7IF APPROPRIATE, zero the XP2iby sending the “!ZER” command, since the zero value will be
clear.

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8IF APPROPRIATE, clear the high and low peak values to the current pressure (zero, if you fol-
lowed step 6) by sending the “!CLR” command.
9If you are logging data, you should log the serial number of the unit for traceability purposes
by using the “?SN#” command. You should also log the product code, hardware revision and
rmware version with the “?VER” command.
10 Disable automatic shutdown with the “!NAO” command.
A quick note about the Bootloader Signature: This string contains a 19 character, product-spe-
cic string (whose contents may vary with product revision), followed by a carriage return (CR),
making the total string length 20 bytes. However, a reset turns the RS-232 interface on and o,
so it may be subject to noise; a NULL may be received before the signature is sent, and the rst
character or so of the Bootloader Signature may be corrupted. A framing error is also possible. The
procedure above will deal with this situation properly. Should you want to parse the bootloader
signature, it has the following format:“=xxxxxxxxxxxxxxxxx=” where xwill vary with
product revision. The bootloader signature is used by the rmware upgrade tool, but should NOT
be used to identify the rmware version; use the“?VER” command for that purpose. If you have a
system that may have Crystal DTG or XP2iunits attached, you can use this signature to determine
which device is in use.
NOTE: Any time you detect the Bootloader Signature, the unit has been reset, or discon-
nected from and reconnected to power; turning the unit on and o with the button will not
send the Bootloader Signature. You can use this behavior to detect a battery change, or a
problem with the XP2i.
Some commands may take up to 500 milliseconds to return a reply. You should always wait at
least 50 milliseconds after each reply is received before sending the next command. After a reset
command it may take up to 15 seconds before the gauge resumes normal operation.
Data transmitted from the XP2iwill always be 7-bit ASCII. Any high-ASCII characters indicate a
line-noise problem, or a problem with the XP2ior PC.
The XP2ihas 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 o, and the serial output will alternate between
the bootloader signature and a line reading “CRC FAIL”. This condition can be recovered from,
in the eld, by reloading the unit’s rmware; contact technical support for details.
Calibration
If adjustment is required, we recommend returning the unit to the factory. Factory service oers
benets you won’t nd anywhere else. We have the facilities to test your gauge at a variety of