28 rate-of'change limit and control limit time, 28 rate-of-change limit and control, Limit time – Toshiba LF600F User Manual
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TOSHIBA
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8.2.28 Rate-Of'Change Limit and Control Limit Time
The rate-of-change limit is used to elimínate high electrical noise contained in the process flow
signal.
To check electrical noise, two parameters are defined: rate-of-change limit (set in percent value of
the span) and control limit time (set in units of seconds). Normally the flowmeter produces the analog
output signal by sampling the flow rate signal at 1/24 (or 1/12) of a second sampling rate. If the
sampled value exceeds the set rate-of-change limit value based on the averaged flow rate value up
until the sampled time, the system will reject that sampled value and instead the averaged value
including the rate-of-change limit value in place of the rejected sampled value will be output.
However, if the limit-exceeding sampled value continues for the same flow direction for more than
the preset control limit time, which data will be used as the output signal. The setting ranges for
these two parameters are as follows:
• Rate-of-change limit
0 to 30% / 50ms (in increments of 0.1%)
• Control limit time:
0 to 20 sec (in increments of 1 second)
Note
If “0” is set in either of these parameters, the rate-of-change limit function is disabled.
You can switch between the rate-of-change limit value and control limit time by the setting item
number.
Rate-of-change limit
Control limit time
LI: LIMIT RATE
L2: LIMIT TIME
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