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GFK-0825F Appendix A Scaling Analog Channels A-5
A
Example of Scaling an Analog Input
A channel is configured in the 0 to 10 volts DC range. It measures a velocity input. Electronic
sensors and mechanical linkage external to the block have determined that an input level of +1.5
volts DC is equal to -20 feet/second (-6 meters/second), and that +9 volts DC is equal to +180
feet/second (+50 meters/second). Plotting these values on a graph shows that a signal of 5 volts
DC corresponds to a speed of 73.3 feet/second.
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+10.0+5.0 +9.0
200
100
Velocity
Input
Voltage
50
150
-50
-20
-60
(+1.5V, -20 ft/sec)
(+9.0V, +180 ft/sec)
For engineering units of feet per second, the following scaling values are used:
Low engineering units = -20 ft/sec
High engineering units = +180 ft/sec
Low internal units = 1500 millivolts
High internal units = 9000 millivolts
An input value of 5.0 volts would be scaled to an engineering value of +00073 (ft/sec).
In this example, scaling to hundredths of feet per second would provide better resolution. The
following scaling values would be used:
Low engineering units = -2000 hundredths ft/sec
High engineering units = +1800 hundredths ft/sec
Low internal units = 1500 millivolts
High internal units = 9000 millivolts
An input value of 5.0 volts would be scaled to an engineering value of +7333 (hundredths ft/sec).