IOtech MultiScan 1200, User Manual

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TempScan / MultiScan User's Manual Chapter 12: System Configuration 175
To Compute the TempScan/1100 Scan Interval
To compute the time interval for the TempScan/1100 to acquire one scan, use the following formulas:
•
For a 60 Hz line cycle: Scan Interval is:
Is-t = [Next highest integer (Dv / 4)] x R1
•
For a 50 Hz line cycle: Scan Interval is:
Is-t = [Next highest integer (Dv / 4)] x R2
Where:
Is-t
= Scan Interval for the TempScan/1100, milliseconds.
Dv
= Disposition, variable number of non-empty 4-channel blocks.
R1
= Sampling Rate, constant of 16.67 milliseconds (per 16-channel block) for a 60-Hz line cycle.
R2
= Sampling Rate, constant of 20.00 milliseconds (per 16-channel block) for a 50-Hz line cycle.
For example, if the nine (9) channels 1, 2, 3, 4, 5, 7, 15, 100, and 101 are configured, then there are
five (5) non-empty 4-channel blocks (refer to the table on disposition). Using the scan interval formula
for a TempScan/1100 system with a 60-Hz line cycle, gives:
Is-t = Next highest integer (5 / 4) x 16.67 millisec.
Is-t = 2 x 16.67 millisec = 33.33 millisec.
However, if nine (9) channels are configured less densely by every fourth channel from channel 4
through 36, then there are nine (9) non-empty 4-channel blocks. Using the same formula gives:
Is-t = Next highest integer (9 / 4) x 16.67 millisec.
Is-t = 3 x 16.67 millisec = 50.00 millisec.
Clearly, despite the identical number of configured channels, the disposition affects the
TempScan/1100 scan interval. Meanwhile, the following table shows how the
fast mode scan rate
varies when the number of configured channels increases where these TempScan/1100 channels are all
adjacent to each other.
Variations of the TempScan/1100 Fast Mode Scan Rate
Number of Number of Scan Rate (Hz)
16-Channel Selected 60-Hertz Line Cycle 50-Hertz Line Cycle
Blocks Channels Hertz milliseconds Hertz milliseconds
1 16
60 16.67 50 20
2 32
30 33.33 25 40
3 48
20 50.00 16.67 60
4 64
15 66.67 12.50 80
5 80
12 83.33 10.00 100
… …
… … … …
10 160
6.00 166.67 5.00 200
… …
… … … …
50 800
1.20 833.33 1.00 1000
… …
… … … …
60 960
0.909 1100.00 0.833 1200
61 976
0.984 1016.67 0.820 1220
62 992
0.968 1033.33 0.806 1240
Note: (1) The number of selected channels refer to configured channels which are all adjacent to
each other. (2) These values were obtained from the above TempScan/1100 scan interval
equations.