ABB IMASI13, Instructions Manual

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Automatic Adjustments and Corrections
User Gain and Offset Adjustment
A user-specified linear adjustment can be applied to the input
signal before it is converted to engineering units. This gain and
offset is applied to the value obtained after all compensation
and correction operations are performed.
User offset and gain compensates input signals for user cor-
rections. For example, if a 0 to 10 VDC analog input is 0.1
VDC too high, the ASI module can compensate for this offset
by adding an offset value of -0.1 for this channel and input
type.
User gain value is multiplied by volts for high level inputs, by
millivolts for low level inputs and thermocouple inputs, and by
ohms for RTD inputs. The default user gain is a value of one.
User offset is added to the input signal. Units of offset are
specified as volts for high level inputs, millivolts for low level
inputs, and ohms for RTD inputs. The default user offset is a
value of zero. Separate user gain and offset values can be
specified for each input channel and each input type. The user
gain and offset values can be set and reset using FC 217. Once
defined, user gain and offset values remain in nonvolatile
memory and are not lost when module power is interrupted.
For more information refer to FC 217 in the
Function Code Function Code Function Code Function Code
Application Manual
Application Manual Application Manual
Application Manual .
Engineering Units Conversion
Thermocouple and RTD inputs are converted to the tempera-
ture units specified in FC 216, either degrees C or F. Conver-
sion tables representing the voltage (or resistance) to
temperature relationship are used for this conversion. The
table used in performing the conversion depends upon the
input signal type specified.
If the input is identified as either millivolt or high level voltage,
then the specified engineering unit zero and span values are
used to convert the input reading to a scaled engineering unit
value. If special calculations need to be performed prior to con-
version to engineering units (external to FC 215 and FC 216
blocks), then the zero and span values specified in the func-
tion code should be set to represent a standard voltage span
for the input. The I/O module FC 216 would then output a