
Chapter 2. SPECIFICATIONS
2 - 25
Filter processing
A/D conversion
Sampling (instantaneous value) processing
Average processing Number average processing
Time average processing
2.5.1 Filter Processing
Filter processing noise or the quick change of input value helps to use a stable digital value compared with
analog value.
PVfn = ( 1 -
α
)
×
PVn +
α
PVfn –
1
PVfn : present filter output value
PVn : present A/D conversion value
PVfn-
1
: previous filter output value
α
: Filter constant(the range: 0.01 to 0.99)
Filter constants used here are 1 to 99.
Ex1) G3F-AD4A/G4F-AD2A
Offset value : –10 VDC, Gain Value : 0 VDC
(Voltage input range : -10 ~ 10 VDC, Digital output range : -192 ~ 16191)
When analog value is changed in the sequence like -10V, -5V, 0V, and 5V, filter output is shown as below.
Ex2) G3F-AD4B
Voltage input range : 1 ~ 5 VDC, Digital output range : 0 ~ 16000
When analog value is changed in the sequence like 1V, 2V, 3V, and 4V, filter output is shown as below.
That is, filter disable allows present A/D conversion value to be displayed and filter enable allows A/D
conversion value to be displayed by filter constant according to the relative importance between present
A/D conversion value and previous value.
2.5 A/D Conversion Characteristics
Value of
α
Filter output value
Remarks
0.01 0
3960
7960
11960
α
leaning to the previous value by 1 %
0.5
0 2000 5000 8500
α
leaning to the previous value by 50 %
0.99 0 40
120
239
α
leaning to the previous value by 99 %
Value of
α
Filter output value
Remarks
0.01 0
3960
7960
11960
α
leaning to the previous value by 1 %
0.5
0 2000 5000 8500
α
leaning to the previous value by 50 %
0.99 0 40
120
239
α
leaning to the previous value by 99 %