Honeywell PPT User Manual page 78

PPTR units only
R E F For absolute type PPTR only. The physical orientation of the PPTR can cause the
pressure reading to be offset from its factory calibrated value, particularly for low pressure
range units. The REF and SET commands can be used to remove this offset. PPTRs are
calibrated with the pressure port oriented down and if the unit is mounted in the applica-
tion with the pressure port down, then no offset correction is required. However, if the
PPTR is to be mounted in an orientation other than pressure port down, then the offset can
be corrected as follows:
1) Orient the PPTR with the pressure port down.
2) Vent the pressure port to atmosphere. Read and record the value of Z= and the current
pressure reading. Execute the following commands:
*ddWE
*ddZ=REF
3) To complete the above offset correction sequence, orient the PPT-R in the application
S E T
mount orientation. Note if the pressure reading has changed and if so, execute the follow-
ing commands;
*ddWE
*dd Z=SET
4) Read the pressure and note that it has moved back to the original reading value. Per-
form an EEPROM store to make the correction permanent.
Note: For gauge type PPTRs, the orientation offset is corrected with the Z=CAL command
after the unit has been mounted in its application orientation.
$ Suspend Continuous Readings
This is not actually a command but a special command header character. During a continuous
pressure reading command, P2 or P4 in RS-232 ring configuration or when the bus noise protection
parameter is used (DO command) in multidrop configuration, a '$' by itself will temporarily stop, or
suspend, transmission. Pressure readings will continue to be taken at the configured rate but will
not be transmitted on the RS-232 outputs. This allows for manual entry of a command when continu-
ous readings are filling the display. Pressure reading transmission will resume when the <cr>
carriage return (ENTER key) is pressed.
Note: Under some conditions it is possible to enter a command that will not cause continuous
readings to resume after entering the <cr> character, in which case a second <cr> will cause the
continuous readings to resume.
Example: *dd P2
$*ddV=
(Start continuous pressure readings)
(Suspend continuous pressure readings to read version number)
(Resume continuous pressure reading after the V= reply)
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