Pressure Systems 9022 - Manual (Page 116)

Pressure Systems, Inc. NetScanner™ System (9016, 9021, & 9022) User’s Manual
www.PressureSystems.com 4 - 6
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.
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.