Mitsubishi Electric MELSEC-Q series User Manual page 56

(b) Operation after an alert was output
When a digital output value is less than the rate alarm upper limit value or more than the rate alarm lower limit
value, Normal (0) is stored in the corresponding bit of Warning output flag (Rate alarm) (Un\G51) for the
channel after an alert was output.
When digital output values in all channels are within the setting range, Warning output signal (X8) turns off, and
the ALM LED turns off.
However, the alarm code 10  which is stored in Latest error code (Un\G19) is not cleared. Clear the alarm
code 10  by turning on then off.
(c) Warning detection period
Set a rate alarm warning detection period to CH Rate alarm warning detection period (Un\G118 to Un\G125).
Set an integral multiple of the conversion cycle as the rate alarm warning detection period for each digital
conversion method. If not, change rates are detected in the maximum cycle that satisfies both of the following.
• Rate alarm warning detection period or less
• Integral multiple of the conversion cycle
Rate alarm warning detection period in case of the following conditions
Ex.
• Digital conversion method: Count average
• Average times: 10
• Sampling cycle: 100ms/8CH
• Rate alarm warning detection period: 4500ms
The conversion cycle is 1000ms (10 (times) × 100 (ms)), and a digital output value is compared in 4000ms
intervals to check the change rate.
(d) Judgement of rate alarm
A change rate is judged that the rate alarm upper limit value and the rate alarm lower limit value are converted
to digital values per rate alarm warning detection period. Set a rate alarm upper limit value and rate alarm lower
limit value to the following buffer memory areas.
• CH Rate alarm upper limit value (Un\G126, Un\G128, Un\G130, Un\G132, Un\G134, Un\G136,
Un\G138, Un\G140)
• CH Rate alarm lower limit value (Un\G127, Un\G129, Un\G131, Un\G133, Un\G135, Un\G137,
Un\G139, Un\G141)
Conversion formula of judgement value for the rate alarm is as follows:
Judgement value for rate alarm
detection (digit)
Item
R
H
R
L
D
Max
t
54
R or R
H
=
1000
Rate alarm upper limit value (Unit: 0.1%/s)
Rate alarm lower limit value (Unit: 0.1%/s)
Maximum digital output value of the input range: 10000
Rate alarm warning detection period (Unit: ms)
L
D
Max
Description
t
1000