4 FUNCTIONS
4.5 Conversion Method
31
4
■
Count average
A multiple input module executes the conversion for a set number of times and averages the total value excluding the
maximum value and the minimum value. The averaged value is stored in the digital output value and the digital operation
value.
The time taken to store the average value obtained by the processing in the buffer memory area is the following value.
Processing time of A/D conversion = Set number of times
×
(Number of A/D conversion enabled channels
×
Conversion
speed (1 ms))
Processing time of temperature conversion = Set number of times
×
(Number of temperature conversion enabled channels
×
Conversion speed (40 ms))
Ex.
The following table shows the processing time with the setting below.
5 (times)
×
4 (CH)
×
40 (ms) = 800 (ms)
An average value is output every 800 ms.
Because the count average requires a sum of at least two counts excluding the maximum and minimum
values, the set number of times should be four or more.
■
Moving average
Converted values for the specified number of times captured every sampling period are averaged and stored in the digital
output value and the digital operation value. As each sampling process moves and averaging is performed, the latest digital
output value and digital operation value are obtained.
Ex.
The following figure shows the moving average processing of when the set number of times is five.
Item
Setting
Input type
Thermocouple
Number of channels where temperature conversion
is enabled
Four channels (CH1 to CH4)
Set number of times
Five times
(1) + (2) + (3) + (4)+ (5)
5
(2) + (3) + (4) + (5)+ (6)
5
(3) + (4) + (5) + (6)+ (7)
5
32000
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10) (11)
(12)
16000
0
0
(a)
(b)
(c)
ON
OFF
1st storage (a)
2nd storage (b)
3rd storage (c)
Data transition in buffer memory
0
3rd storage (c)
Time [ms]
2nd storage (b)
1st storage (a)
Sampling cycle
Digital output value
'CH1 Digital output value'
(Un\G400)
'A/D conversion
completed flag'
(Un\G69, b14)
Summary of Contents for MELSEC iQ-F
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