Pressure Systems 9022 Manuel d'utilisateur télécharger pdf (Page 118)

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

4 - 6

4.3 Span Calibration

For improved accuracy, the NetScanner



System Intelligent Pressure Scanners are capable of

independently performing a transducer calibration function, referred to as Span adjustment (or

simply Span Cal). Actually, there is a provision to supply any suitable “upscale” pressure (e.g.,

actual transducer full-scale) during such a calibration adjustment. The Span adjustment

calibration will result in a recalculated “gain” coefficient for each channel being calibrated, to

compensate for any transducer or module gain errors. For best results, a Re-zero calibration

should be performed before performing a span calibration. Also, note that a new and improved

Multi-Point Calibration function exists (for modules with firmware version 2.24 of higher).

This function integrates the separate calibration functions (for Re-zero and Span adjustment

described in Section 4.2 and this section) into a single function that adjusts both “offset” and

“gain” coefficients at the same time, using two or more calibration points. Details of using this

improved calibration function are described in Section 4.4.

For Model 9016, with integral DH200 transducers, internal manifolds and valves allow a Span

adjustment pneumatic calibration to be accomplished easily and automatically. For Models

9021 and 9022, which have external 9400, 9401 or 9402 (or third-party) all-media transducers,

the user must supply any necessary valves and controls to accomplish the application of an

upscale pneumatic or hydraulic pressure to these transducers before executing the span

adjustment.

It is recommended that a Span adjustment be performed whenever new transducers are installed

in the instrument. In such cases, the new gain coefficients that result should always be stored

back into the transducer’s non-volatile memory. In other cases, the user’s application may not

require periodic span adjustment since the other factory-determined pressure/temperature

coefficients (stored permanently inside each transducer) are extremely stable. Only an

occasional Re-zero adjustment may be all that is necessary.

When instructed to execute a Calculate and Set Gains (‘Z’) command, the module will perform

the Span adjustment calibration, and then update the gain coefficients in its memory. It will

subsequently use the newly calculated gain terms for subsequent engineering-unit calculations

until power is lost to the module.

NOTE: When using the Calculate and Set Gain (‘Z’) command, only the local variables

in the module’s volatile main memory (RAM) are changed. Refer to Section 4.6 if it is

desired to also store these new gain coefficients in transducer nonvolatile memory.

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Pressure Systems 9022 Manuel d'utilisateur Page 118