Published: July 18, 2008
Analog output point inverted scaling may be unstable
Versions affected: SNAP PAC firmware R8.0a and higher
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.
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).
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