Mitsubishi Electric MELSEC iQ-R Series User Manual page 23

Primary delay filter
A temperature input module performs the conversion where the transient noise of temperature input is smoothed depending
on the set time constant. The smoothed measured temperature value is stored in the buffer memory area.
Time constant is the time taken for the measured temperature value to reach 63.2% of the steady-state value. The degree of
smoothing changes depending on the setting of a time constant. A time constant is calculated by the following formula.
• Time constant = Conversion speed  Setting value of 'CH1 Time average/Count average/Moving average/Primary delay
filter constant setting' (Un\G502)
The following table lists the relational expressions of time constants, measured temperature values, and present number of
sampling (n).
Present number of sampling
n = 1
n = 2
n  3
'Conversion completed flag' (XE) turns on when n  2.
Ex.
Measured temperature value when a temperature input value of the thermocouple input module is changed from 250.0 to
260.0
The following figure shows the change of the measured temperature value with the time constant set to be 40 times (1200ms).
After 1200ms from when the temperature input value becomes 260.0, the measured temperature value reaches 63.2% of
its change range from the value when the sampling processing is selected.
Temperature input value
262
260
258
63.2%
Temperature input
256
value (­)
254
252
250
0
Relational expression
Yn = 0
Δt
Y = X + (X - X
n
n n-1
Δt + TA
Δt
(X - Y
Y = Y +
n
n n-1
Δt + TA
Measured temperature value
1200
Elapsed time (ms)
Element
Y : Present measured temperature value
n
Y : Last measured temperature value
n-1
n: Number of sampling
)
n-1 X : Measured temperature value before smoothing
n
X : Last measured temperature value before
n-1
smoothing
t: Conversion time
)
n-1
TA: Time constant
2620
2600
2580
2560
2540
2520
2500
1.4 Temperature Conversion Method
Measured temperature
value
1 FUNCTIONS
1
21