Watlow CAS200 - Manual (Page 101)

CAS200 User’s Guide Chapter 6: Linear Scaling Examples
Watlow Anafaze 89
Example 2: 0-5Vdc Sensor
Situation
A flow sensor connected to the scanner measures the flow
in a pipe. The sensor generates a 0-5V signal. The sensor's
output depends on its installation. Independent calibration
measurements of the flow in the pipe indicate that the
sensor generates 0.5V at three gallons per minute (GPM)
and 4.75V at 65 GPM. The calibration instruments are
accurate to within one gallon per minute.
Setup
The sensor is connected to a loop input set up with a
resistor voltage divider network to produce 60mV at 5V.
The INPUT TYPE for the loop is set to LINEAR. The
calibrating instrument is ±precise to ±1 GPM, so the DISP
FORMAT
is set to -999 TO +3000.
This table shows the input readings and percentage
calculation from the 60mV full scale input.
Table 6.3 Input Readings and Calculations
Table 6.4 Scaling Values
Process
Variable
Displayed
Sensor
Input
Reading, Percent of
Full Scale (%FS)
65 GPM 4.75 (4.75V/ 5.00V) x 100% = 95%
3 GPM 0.5 (0.5V/ 5.00V) x 100% = 10%
Parameter Prompt Value
High Process Variable HIGH PV 65 GPM
High Sensor Reading HIGH RDG 95.0%FS
Low Process Variable LO PV 0.0 GPM
Low Sensor Reading LO RDG 10.0%FS