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GFK-0825F Chapter 5 Station Configuration 5-97
5
Output Scaling
If engineering and span values for a channel are entered during configuration rather than being set
by a default range, “NONE” is displayed on the Default Range screen. “NONE” can then be
selected again but will have no effect on the module configuration. The module performs its own
scaling (unlike conventional Field Control analog modules, whose scaling is performed by the
BIU).
Custom Scaling
To scale a channel, choose a high and low point and enter the actual input value (span) and a
corresponding engineering units value for each point. During operation, the module will use these
values to convert engineering units into digital values that represent output current. Engineering
units values are 16-bit signed integers from -32,768 to 32,767. Span values are unsigned integers
ranging from 0 to 20,000.
The engineering and span points you select do not limit the actual hardware output range. For
example, a channel whose range is configured to 1 will output current below 4mA for engineering
units values below 4,000 even though the low span value is 4mA. It is possible to choose scaling
parameters that will cause the current output to be limited by the scaling process. For example,
using a low engineering units value of -32,768 (minimum value) and a high engineering units value
of 32,767 (maximum value) would effectively limit the output current to values between the
corresponding low and high span values.
The first scaling screen shows the engineering units (AQ) value that corresponds to the low span
(output) value. Valid engineering units are -32768 to 32767.
S:1 CH1 ENG L
04000
< > chg entr
1. If you want to change the displayed selection, press F3 (chg).
2. Enter the new value using the numeric keypad.
3. Press F4 ( entr) to enter the new value or F3 (clr) to abort the change.
The high engineering units value for the channel is displayed next.
S:1 CH1 ENG H
20000
< > chg entr
If the low and high engineering units values are equal, the output of the channel is:
the minimum output level (0mA) if the AQ data is less than the low engineering units value.
the maximum output level (approximately 20mA) span value if the AQ data is greater than or
equal to the low engineering units value.