Reference Manual
00809-0100-4664, Rev BA
January 2010
4-33
Rosemount 8712
For example, if the number of samples selected is 100, then the response
time of the system is 10 seconds. In some cases this may be unacceptable.
By setting the time limit, you can force the 8712 to clear the value of the
running average and re-establish the output and average at the new flow rate
once the time limit has elapsed. This parameter limits the response time
added to the loop. A suggested time limit value of two seconds is a good
starting point for most applicable process fluids. The selected signal
processing configuration may be turned ON or OFF to suit your needs.
Coil Drive Frequency
Coil drive frequency allows pulse-rate selection of the sensor coils.
5 Hz
The standard coil drive frequency is 5 Hz, which is sufficient for nearly all
applications.
37 Hz
If the process fluid causes a noisy or unstable output, increase the coil drive
frequency to 37 Hz. If the 37 Hz mode is selected, perform the auto zero
function with no flow and a full sensor.
Low Flow Cutoff
Low flow cutoff allows you to specify the flow rate, between 0.01 and 38.37
f/s, below which the outputs are driven to zero flow. The units format for low
flow cutoff cannot be changed. It is always displayed as feet per second
regardless of the PV Units format selected. The low flow cutoff value applies
to both forward and reverse flows.
Primary Variable Damping
0 to 256 Seconds
Primary Variable Damping allows selection of a response time, in seconds, to
a step change in flow rate. It is most often used to smooth fluctuations in
output.
Field Comm. 1, 4, 4, 3
LOI Key AUX. FUNCTION
Field Comm. 1, 4, 4, 4
LOI Key AUX. FUNCTION
Field Comm. 1, 4, 4, 5
LOI Key DAMPING
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