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Section 3-7
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3-7-2
Rate Measurement
For every Counter the Rate of the incoming pulses can be measured, for Units
either in Range Mode or Comparison Mode. The measured Rate Values can be
used in the Ladder Program for Frequency or Rotational Speed calculations or for
monitoring purposes. Additionally, for every Counter two Rate Ranges can be con-
figured, both consisting of a Lower- and Upper Rate Range Limit. For every Rate
Range an Output Set & Reset Pattern can be defined to control all 32 outputs
accordingly. Set/Reset actions as defined in this Output Set & Reset Pattern to
control the Outputs, overrule the Unit Output Pattern for the corresponding Out-
puts. This allows you to detect too high or too low frequencies (and speeds) and
enables you to control the Outputs accordingly.
Rate Value Calculation
If you want to use Rate Measurement for a Counter you must start by defining the
Time Window. You can set the Time Window between 1 ms and 9999 ms, in steps
of 1 ms (BCD). The number of pulses which are received during the Time Window
are automatically calculated by subtracting the Counter Value at the beginning of
the Time Window from the Counter Value at the end of the Time Window.
Rate Measurement can be done for all Input Signal Types (refer to 3-3
). Calculating the Rate Value in this way implies that a change of the
counting direction during the Time-Window is reflected in the Rate Value. For illus-
tration refer to the next example:
The Counter Value (T0) at the beginning of the Time-Window is +5. During the
Time-Window 5 up counts and 15 down counts are received. The Counter Value
(T1) at the end of the Time-Window will then be –5. The Rate Value is –10.
Note
1. For Phase Differential Signals (multiplication x2 and x4) pulses are counted on
both edges of A or both edges of A and B respectively. If you want to calculate
the pulse Rate Value for these signals, you must divide the measured Rate Val-
ues by 2 and 4 respectively.
2. The Rate Value that is calculated after a Preset or Reset of a Counter, will be
replaced by the Rate Value calculated before the Preset or Reset took place.
T0
T1
T2
Count Pu lses
Time Base
Time Window
Time Window
Current
Counter Value (T0)
Current
Counter Value (T1)
Current
Counter Value (T2)
Rate V alue 1 = CCV ( T1) - CCV (T0)
Rate V alue 2 = CCV ( T2) - CCV (T1)
...
Rate V alue n = CCV ( Tn) - CCV (T(n-1))
CCV = Current Counter Value
Time Window = [1, 9999 ms]
W902-E2-03.book Seite 83 Donnerstag, 7. Oktober 2004 2:06 14
Содержание CS1W-CT021
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