Watlow CAS200 - Manual (Page 102)

Chapter 6: Linear Scaling Examples CAS200 User’s Guide
90 Watlow Anafaze
Example 3: Pulse Encoder
Situation
A pulse encoder which measures the movement of a
conveyor is connected to the scanner. The encoder
generates 900 pulses for every inch the conveyor moves.
You want to measure conveyor speed in feet per minute
(FPM).
Setup
The encoder input is connected to the scanner’s pulse input.
The INPUT TYPE for the loop is set to PULSE. A one-second
sample time gives adequate resolution of the conveyor's
speed.
The resolution is:
1 pulse 6 0 seconds 1 inch 1 foot
––––––– x ––––––––– x ––––––––– x –––––– = 0.006FPM
1 second 1 minute 900 pulses 12 inches
A DISPLAY FORMAT of -99.99 TO +300.00 is appropriate.
The input readings are as follows:
• At 0Hz, the input reading will be 0.00 FPM.
• At the maximum pulse rate of the CAS200 (2000Hz):
200 pulses 60 seconds 1 inch 1 foot
–––––––––– x ––––––––– x ––––––––– x –––––– = 11.11FPM
1 second 1 minute 900 pulses 12 inches
Table 6.5 Scaling Values
Parameter Prompt Value
High Process Variable HIGH PV 11.11 FPM
High Sensor Reading HIGH RDG 2000Hz
Low Process Variable LO PV 0 FPM
Low Sensor Reading LO RDG 0Hz