Allen-Bradley 1756-CFM, Руководство пользователя

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Rockwell Automation Publication 1756-UM010C-EN-P - June 2021 33
Chapter 3 Configurable Flowmeter Module Features and Operational Modes
Acceleration Calculation
Acceleration Calculation is derived by using the rate of change of frequency
over a specified number of samples (1 to 255). This moving average produces
quick responses when the number of samples = 1 and stable, but slower,
responses when the number of samples =255.
The default number of samples used = 255, but a typical application uses 50
samples. There are significant differences between response times. For
example, the quick response offer acceleration calculations more often but is
more likely to set off the Acceleration Alarm for calculation spikes at low
frequencies. The stable responses are slower but ignore acceleration spikes in
favor of definitive operational trends.
Meter Factor
Meter Factor is used to calibrate the frequency (Hz) to a user-defined standard.
For example, the module can read 59.9 Hz while the standard is set for 59.7 Hz.
In this case, the meter factor (default = 1.0) should be changed to 0.99666 to
correct the reading.
Trigger On
Use Trigger On to determine what state triggers an output to energize in High
Resolution Frequency mode (that is, an output can be configured to turn ON if
the Frequency Average reaches a particular frequency.
• Frequency - Input exceeds MaxAllowedFreq.
• Acceleration - Input speed accelerates beyond AccelAlarmValue.
Tie to Counter
Choose which output is connected to which flowmeter input.
IMPORTANT
Acceleration Calculation values can be entered on the bit level or byte
level. If you are entering values at the byte level, you must use -1 to
represent 255. If you are entering values on the bit level, you can use the
actual number value.
IMPORTANT For the Trigger On feature, Frequency and Acceleration are tied to the
Overspeed Alarm and Acceleration Alarm respectively. The alarms
remain latched ON once set and can only be reset if you toggle the Alarm
Enable bits.