Pressure Systems 9022 Manuel d'utilisateur télécharger pdf (Page 43)

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

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inputs (CAL side inputs) and calibration manifolds required for directing the generated pressures

to the various channels of the module(s) being calibrated. Models 9021 and 9022 require such

pneumatic/ hydraulic plumbing be provided by the customer (if deemed necessary). Refer to

Chapter 4 of this manual for detailed background and procedures for periodic calibration

of the Intelligent Pressure Scanners. A summary of the commands used for calibration

purposes is included below.

The Calculate and Set Offsets (‘h’) command is executed only when a suitable “minimum” (e.g.,

zero) pressure has been applied to all channels of the module. The new offset coefficients that

result from execution of this command are stored in the module’s volatile (or temporary)

engineering-unit conversion database. They are also returned to the host in the command’s

response.

The Calculate and Set Gains (‘Z’) command should be executed only when “full-scale” (or other

suitable specified up-scale) pressure has been applied to the appropriate channels of a module.

The new gain coefficients that result from this command are stored in the module’s volatile (or

temporary) engineering-unit conversion database. They are also returned to the host in the

command’s response.

In modules using firmware version 2.24 or later, a Configure/Control Multi-Point Calibration

(‘C’) command is provided. This command (actually 4 sub-commands) is an improvement over

the single calibration commands (‘h’ and ‘Z’) described above. Though ‘C’ provides for the

adjustment of the same offset and gain correction coefficients already described above, it does so

with two or more applied pressure calibration points. The final linear fit (i.e., new offset and

gain correction coefficients) is a “least squares” correction fit between all the calibration points

specified. This ‘C’ command is particularly useful in calibrating differential transducers over

their entire negative-to-positive range.

Although the calculated offset and gain correction coefficients are kept in volatile memory

following execution of the calibration commands, they may be stored in non-volatile transducer

memory following the execution of the calibration commands (for use by all subsequent EU

conversions).

This is accomplished with the Set/Do Operating Options (‘w’) command (Index 08 and 09).

The above correction coefficients are maintained internally in IEEE floating-point format. The

Read Internal Coefficients (‘u’) command and the Download Internal Coefficients (‘v’)

command can return (or manually set) calibration coefficients to the host in decimal or hex dump

formats in their responses.

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Pressure Systems 9022 Manuel d'utilisateur Page 43