Mitsubishi Electric MELSEC iQ-F FX5 User Manual page 41

■Judgment of rate alarm
A change rate is judged with "Rate alarm upper limit value" and "Rate alarm lower limit value" converted to digital values per
rate alarm warning detection period.
The following shows the conversion formula of judgment values used for the rate alarm detection.
Value used for judgment in every
rate alarm alert detection cycle [digit]
Ex.
The judgment value under the following conditions
Setting item
Averaging process specify
Rate alarm warning detection period setting
Rate alarm upper limit value
Rate alarm lower limit value
Upper limit value: 2500.10.0116000=4000 (digit)
Lower limit value: 500.10.0116000=800 (digit)
The current value is compared with the previous value in every rate alarm warning detection period ("10 ms" in this example).
It is checked whether the current digital value is larger by more than 4000 digit (25 %) or smaller by more than 800 digit (5.0
%) compared to the previous value.
The following formula is used to obtain the change rate to be set based on the change amount of the voltage/current to detect
warning:
Change rate to be set (0.1 %) =
*1 The value below the decimal point obtained by calculation is rounded.
■Application examples of rate alarms
A rate alarm serves to monitor that the variation rate of a digital output value lies in a limited range as shown below:
Ex.
To monitor that a rising rate of a digital output value is within the specified range
Change rate of the digital output value (%)
+30 %
+20 %
0
Ex.
To monitor that a drop rate of a digital output value is within the specified range
Change rate of the digital output value (%)
0
-20 %
-30 %
= "Rate alarm upper limit value (lower limit value)" × 0.1 × 0.01 ×
*1
Maximum digital output value
Description
Sampling processing
10 (ms)
250 (25.0 %)
50 (5.0 %)
Change amount of the voltage (current) to detect warning (V (mA))
Gain voltage (current) (V(mA)) - Offset voltage (current) (V (mA))
Rate alarm upper value
Rate alarm lower value
Rate alarm upper value
Rate alarm lower value
× 1000
Time
Time
2 FX5-4AD-ADP
2
*1
39
2.3 Functions