User`s guide

Page 18

Controlinc 1746-C (Version 5.21) Network Master Users Guide (2004-11-18)

4.1.3. Diagram Demonstrating Adding Additional Valves in Valve Scan

Time-Slice

This example demonstrates how increasing the additional number of valves to be scanned before

servicing the PLC communication task decreases the total network scan time.

This is where the PLC/HMI must make a value decision for the best fit for their application:

• Increasing the number: Speeds up data collection Lowers PLC control capabilities.

• Decreasing the number: Slows down data collection Increases PLC control capabilities.

Example of scale for time to scan network … different values for Additional valves in scan time slice:

Network size: 8 Network size: 8

Additional valves: 0 Additional valves: 3

(Note the relative time differences are for illustration purposes only … not to any exact scale.)

Poll 1 valve for data

Service PLC cmd

Poll 1 valve for data

Service PLC cmd

Poll 1 valve for data

Service PLC cmd

Poll 1 valve for data

Service PLC cmd

Poll 1 valve for data

Service PLC cmd

Poll 1 valve for data

Service PLC cmd

Poll 1 valve for data

Service PLC cmd

Poll 1 valve for data

Service PLC cmd

Poll 4 valves for data

Service PLC cmd

Poll 4 valves for data