Allen-Bradley MicroLogix 1200 Reference Manual page 267

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.
Process Control Instruction 19-25
Publication 1762-RM001C-EN-P