Linear scaling examples, Example 1 – Watlow CLS User Manual
Page 123
Linear Scaling Examples
CLS User’s Guide 115
Linear Scaling Examples
Example 1
Situation
A pressure sensor that generates a 4-20 milliamp signal is connected to
the CLS. The specifications of the sensor state that it generates 4
milliamps at 0.0 PSI and 20 mA at 50.0 PSI.
Setup
The sensor is connected to a loop input set up with a resistor scaling
network to produce 60 millivolts at 20 mA. (See the Inputs section of
Installation for more information on scaling networks.)
The sensor measures PSI in tenths, so the appropriate display format is -
999.9 to +3000.0.
This table shows the input readings.
The scaling values are therefore:
PV
Displayed
Sensor Input
Reading (%FS)
50.0 PSI
20
100%
0.0 PSI
4
100%x(4ma/20 ma) = 20%
Parameter
Low Value
High Value
Process Value (PV)
0.0 PSI
50.0 PSI
Input Reading (RDG)
20.0
100.0