Allen-Bradley micrologix 1500 - Page 267

Publication 1762-RM001C-EN-P
Process Control Instruction 19-25
Verifying the Scaling of Your Continuous System
To ensure that your process is linear, and that your equipment is properly
connected and scaled, do the following:
1. Place the PID instruction in MANUAL and enter the following
parameters:
– type:
0
for MinS
– type:
100
for MaxS
– type:
0
for CO%
2. Enter the REM RUN mode and verify that PV=0.
3. Type:
20
in CO%
4. Record the PV = _______
5. Type:
40
in CO%.
6. Record the PV = _______
7. Type:
60
in CO%.
8. Record the PV = _______
9. Type:
80
in CO%.
10. Record the PV = _______
11. The values you recorded should be offset from CO% by the same
amount. This proves the linearity of your process. The following
example shows an offset progression of fifteen.
– CO 20% = PV 35%
– CO 40% = PV 55%
– CO 60% = PV 75%
– CO 80% = PV 95%
If the values you recorded are not offset by the same amount:
•
Either your scaling is incorrect, or
•
the process is not linear, or
•
your equipment is not properly connected and/or configured.
Make the necessary corrections and repeat steps 2-10.