149
CHAPTER 8 FUNCTIONS
8
8.13 F
requ
ency Measureme
nt Function
●
Whichever mode ("1: 1-Phase Multiple of 2", "4: 2-Phase Multiple of 2", or "5: 2-Phase Multiple of 4") is set in "CH
Pulse
input mode" (
Page 92, Section 8.1.1), the frequency (Hz) is calculated based on the count value per unit of time.
●
When "1: 1-Phase Multiple of 2" is set in "CH
Pulse input mode" (
Page 92, Section 8.1.1) and the input frequency
in phase A is 10kHz (10000 per second), the measured frequency value becomes 20kHz since the pulse count is
regarded as 20000 based on the calculation below.
Pulse count = 10000 (pulse) × 2 = 20000 (pulse/s)
●
Measurable frequency (minimum)
The frequency is calculated from the count value per unit of time. However, the frequency smaller than the one in the
following table cannot be measured correctly as the count value is in an integer number.
When a unit of time is 0.01s and the input frequency is 1234Hz, the measured frequency value is 1200Hz or 1300Hz. By
doing the moving average count, the fluctuation of the measured values can be lowered.
(4) Moving average count
When the frequency measurement function is used, the fluctuation of the measured frequency values can be
lowered by doing the moving average count.
Set the number of the moving average count to CH
Moving average count (Frequency measurement) (RWw19,
RWw31).
After the specified number of counts are done, the average of the measured frequency values is stored in CH
Measured frequency value (RWr1A to RWr1B, RWr32 to RWr33) as shown below.
Ex.
When the number for CH
Moving average count (Frequency measurement) (RWw19, RWw31) is set to
3
Unit of time
Measurable frequency (minimum)
1s
1Hz
0.1s
10Hz
0.01s
100Hz
Setting item
Setting range
Reference
CH
Moving average count (Frequency measurement)
(RWw19, RWw31)
1 to 100
(When 1 is set, the operation is performed
with the moving average count regarded as
not being done.)
CH Count enable command
(RY24, RY3C)
10000
Frequency
1)
2)
3)
4)
5)
5000
0
Time
T: Time unit
1st storage
1st storage = 1)+2)+3)/3 = (5000+7000+8000)/3 6667
2nd storage = 2)+3)+4)/3 = (7000+8000+8000)/3 7667
3rd storage = 3)+4)+5)/3 = (8000+8000+4000)/3 6667
Remote register
CH Measured
frequency value
(RWr1A to RWr1B,
RWr32 to RWr33)
2nd storage
3rd storage
T
T
T
T
T
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