Pressure Systems, Inc. Model 9116 User’s Manual
Page 63
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 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 or zero-only calibration.
Command
“
hpppp [vv.vvvv]
”
‘
h’ is the
command
letter
‘
pppp
’ is the
position
field
‘
vv.vvvv
’
is an [optional]
applied 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 of a module’s input channels 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, the position field must be 4 characters, even when
all channels are to be specified. If the
optional pressure value
[‘
vv.vvv
’] is not
provided, an applied pressure of 0.0 psi(a) will be assumed when calculating
coefficients. 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).
Before acquiring data with this command, any addressed
Model 9116
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 non-volatile memory refer to the
Set Operating Options
(‘w’) command (index 08).
