Emerson 8800A, Product Manual

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Rosemount Model 8800C Vortex Flowmeter
3-22
Low Flow Cutoff
Low Flow Cutoff enables you to adjust the filter for noise at no flow. It
is set at the factory to handle most applications, but certain
applications may require adjustment either to expand measurability or
to reduce noise.
The Low Flow Cutoff offers two modes for adjustment:
• Increase Range
• Decrease No Flow Noise
It also includes a dead band such that once flow goes below the cutoff
value, output does not return to the normal flow range until flow goes
above the dead band. The dead band extends to approximately 20
percent above the low flow cutoff value. The dead band prevents the
output from bouncing between 4mA and normal flow range if the flow
rate is near the low flow cutoff value.
Low Pass Filter
The Low Pass Filter sets the low-pass filter corner frequency to
minimize the effects of high frequency noise. It is factory set based
on line size and service type. Adjustments may be required only if
you are experiencing problems. See Section 4: Troubleshooting
and Maintenance.
The Low Pass Filter corner frequency variable offers two modes for
adjustment:
• Increase filtering
• Increase sensitivity
Trigger Level
Trigger Level is configured to reject noise within the flow range while
allowing normal amplitude variation of the vortex signal. Signals of
amplitude lower than the Trigger Level setting are filtered out. The
factory setting optimizes noise rejection in most applications. Trigger
Level offers two modes for adjustment:
• Increase filtering
• Increase sensitivity
NOTE
Do not adjust this parameter unless directed to do so by a Rosemount
Technical Support Representative.
HART Comm. 1, 4, 4, 2, 3
HART Comm. 1, 4, 4, 2, 4
HART Comm. 1, 4, 4, 2, 5