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MELSEC-Q
3 SPECIFICATIONS
(3) Primary delay filter
A digital value whose transient noise has been smoothed is output according to
the preset time constant.
The degree of smoothing varies with the time constant setting.
The relational expression of the time constant and digital output value is indicated
below.
[If n = 1]
Yn = 0
[If n = 2]
t
Yn = yn-
1
+
t + TA
(yn - yn-
1
)
[If n 3]
t
Yn = Yn-
1
+
t + TA
(yn - Yn-
1
)
Yn: Current digital output value yn: Pre-smoothing digital output value
Yn-
1
: Immediately preceding digital
output value
Yn-
1
: Immediately preceding
pre-smoothing digital output value
n: Sampling count
t: A/D conversion time (0.01s)
TA: Time constant (s)
The A/D conversion completed flag turns ON when n 2.
[Example 1] Digital output value when the analog input value varied from 0 to 1V
The variation of the digital output value at the time constant setting
of 1000ms (1s) is as shown below.
1000ms (1s) after the analog input value has reached 1V, the digital
output value reaches 63.2% of the value attained when the sampling
processing is selected.
0 1000
0
0.2
0.4
0.6
0.8
1
1.2 12000
10000
0
2000
4000
6000
8000
Analog input value Digital output value
Elapsed time (ms)
Digital output value
Analog input value (V)
[Example 2] Digital output value when the variation of the analog input value has
a ringing waveform
The variations of the digital output values at the time constant setting
of 2000ms (2s), at the time constant setting of 1000ms (1s), and at
the move averaging processing of 16 times are as shown below.
0
0
0.2
0.4
0.6
0.8
1
1.2
12000
10000
0
2000
4000
6000
8000
Analog input value (V)
Digital output value
(time constant setting: 1000ms)
Analog input value
Digital output value
(move averaging processing: 16 times)
Digital output value
(time constant setting: 2000ms)
Elapsed time (ms)
Digital output value
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