KB54754
Published: July 18, 2008
Revision: 1.0

Analog output point inverted scaling may be unstable


Applies To:

SNAP-PAC-R1
SNAP-PAC-R2
SNAP-PAC-EB1
SNAP-PAC-EB2
SNAP-UP1-ADS
SNAP-UP1-M64

Versions Affected:

Versions affected: SNAP PAC firmware R8.0a and higher


Symptoms:

You can use custom scaling to invert readings for analog input points. Inverted scaling accommodates field devices (sensors) that are wired to the SNAP module in a way that produces a negative current or voltage. Inverted scaling lets the analog input module accommodate the negative reading so that it represents a full-scale value.

Inverted scaling is currently not supported for analog output points. If an analog output point is configured with inverted scaling, unstable results may be produced.

Example:

A SNAP-AOA-23-iSRC, 4- 20 mA output module is configured with inverted scaling so that 4 mA (4095 counts) is the upper scaled units, and 20 mA (0 counts) is the lower scaled units. During normal operation, an upper scale reading of 4 mA (4095 counts) may unexpectedly read 20 mA (0 counts).


Questions?

Contact: Opto 22 Product Support.
Phone: 800-835-6786 or 951-695-3080
Email: support@opto22.com


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