Mitsubishi Q64AD-GH User Manual page 35

3 SPECIFICATIONS
3 - 12
(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]
Yn = yn- +
1
[If n 3]
Yn = Yn- +
1
Yn: Current digital output value
Yn- : Immediately preceding digital
1
output value
n: Sampling count
TA: Time constant (s)
The A/D conversion completed flag turns ON when n
[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.
1.2
1
0.8
0.6
0.4
0.2
0
0
[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.
1.2
1
0.8
0.6
0.4
0.2
0
0
t
(yn - yn- )
1
t + TA
t
(yn - Yn- )
1
t + TA
Analog input value
1000
Elapsed time (ms)
Analog input value
Digital output value
(move averaging processing: 16 times)
yn: Pre-smoothing digital output value
Yn- : Immediately preceding
1
pre-smoothing digital output value
t: A/D conversion time (0.01s)
2.
Digital output value
Digital output value
(time constant setting: 1000ms)
Digital output value
(time constant setting: 2000ms)
Elapsed time (ms)
MELSEC-Q
12000
10000
8000
6000
4000
2000
0
12000
10000
8000
6000
4000
2000
0
3 - 12