Mitsubishi Electric MELSEC iQ-F FX5 User Manual page 32

Primary delay filter
Depending on the set time constant, transient noise of analog input is smoothed and stored in the digital output value and
digital operation value area.
The degree of smoothing varies depending on the setting of a time constant (s).
Time constant is the time taken for the digital output value to reach 63.2% of the steady-state value.
The following shows the relational expressions of time constants and digital output values.
*1
When n = 1
Y = 0
n
When n = 2
Δt
Y = X +
n n-1
Δt + TA
When n  3
Δt
Y = Y +
n n-1
Δt + TA
Y : Present digital output value
n
Y : Last digital output value
n-1
n : Number of sampling
X : Digital output value before smoothing
n
X : Last digital output value before smoothing
n-1
T
: Conversion time
TA : Time constant
*1 A/D conversion completed flag turns on when n  2.
Time constant = [Primary delay filter constant set by "CH1 Time average/Count average/Primary delay filter
constant setting" (Un\G502)] × [Conversion cycle].
Ex.
Digital output value when an analog input value is changed 0  1 V
The following figure shows the change of the digital output value with the input range of 0 to 10 V and time constant
(Conversion cycle  Primary delay filter) of 40 ms.
After 40 ms from the analog input value becomes 1 V, the digital output value reaches 63.2% of the digital output value of
when the sampling processing is selected.
1.2
1.0
0.8
Analog input voltage (V) 0.6
0.4
0.2
1 FX5-4AD
30
1.4 Functions
(X
- X )
n n-1
(X - Y )
n n-1
Analog input value
63.2%
0
0 40
Digital output value
Elapsed time (ms)
3840
3200
2560
1920 Digital output value
1280
640