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KB54754
Analog output point inverted scaling may be unstable
Revision:  1.0
Published:  7/18/2008
Applies To
Firmware for:
SNAP-PAC-R1
SNAP-PAC-R2
SNAP-PAC-EB1
SNAP-PAC-EB2
SNAP-UP1-ADS
SNAP-UP1-M64
Versions
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).

Relevant Downloads
No relevant downloads have been specified.
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