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Measurement Specialties Inc. NetScanner System (9016, 9021, & 9022) User’s Manual

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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. When using the 9021/9022 module with 9401 absolute pressure

transducers, it will usually be required to use the applied pressure field [‘vv.vvv’]

as it may not be possible to apply 0.0 psia to the 9401 transducers. 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 9016 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

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Pressure Systems 9022 Manuel d'utilisateur Page 81