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Pressure Systems, Inc. 98RK-1 & 9816 User’s Manual©
Page 74 www.PressureSystems.com
CALCULATE AND SET OFFSETS (Command 'h')
Purpose: Instructs a module to calculate new offset coefficients, with zero differential
pressure (or a specified “generated” pressure) applied to the specified internal
channels. These new coefficients update part of the module’s internal calibration
coefficient database, used to convert any subsequent raw data into engineering
units data. The new offset values are also returned in the response. This
command is sometimes called a Re-zero calibration.
Command
“hpppp[ vv.vvvv]”
‘h’ is the command letter
‘pppp’ is the position field
‘ vv.vvvv’ is an [optional] pressure value preceded by a space
character.
Response
“ g.gggg[ g.gggg]...”
‘ g.gggg’ are the actual offset data values returned, each preceded by
a space.
Description: The position field may have 0 or 4 characters. If no position field is specified,
offset coefficients for all internal module channels (16-1) will be calculated and
returned. If a position field is specified, offset coefficients for only the channels
whose bits are set (=1) will be calculated and returned. If the optional pressure
value [ vv.vvvv] is specified (rarely used), the position field must be 4 characters,
even when all channels are to be specified. Offset values are returned in the
response in order of highest specified channel to lowest specified channel, with
data formatted per an implied decimal format (f=0).
NOTE: This command may only be applied to the sixteen (16) internal channels. It is not
applicable for the external 98RK-1’s purge/supply (P & S) channels.
Before acquiring data with this command, any addressed Model 9816 module will
normally attempt to place the calibration valve in the CAL position, so that a zero
differential pressure can be applied to all channels via the module’s CAL and
CAL Ref input port. Simply leaving these ports unattached will allow the
transducers to read the appropriate zero differential pressure if ambient air
pressure is stable. After data are acquired, the calibration valve will be placed in
the RUN position. To disable the automatic shifting of the calibration valve, refer
to the Set Operating Options ('w') command (index 0B). The reader is also
referred to Section 4.2 of Chapter 4 for additional details concerning the
performance of a Re-zero Calibration.
Note
The calculated offset values from the latest 'h' command will be lost
when the module is powered off. To save these offset terms to each
transducer’s nonvolatile memory refer to the Set Operating Options
('w') command (index 08).