26
PROGRAMMING cont.
the display will flash all 9s. So, if youre trying to show barrels per day and youre
running above 1 million barrels per day, change the rate time units to 3600 and
show barrels per hour instead.
The rate smoothing factor parameter F4 provides a filtering effect on the rate display
when flow rate changes. The ratemeter updates every 0.5 seconds. Since the rate-
meter is deadly accurate, if flow rate changes, the rate display will change. In some
systems, the rate display will bounce around due to fluctuations in flow rate. A rate
smoothing factor of 1 causes no filtering to occur. This is useful when the user must
be quickly made aware via the display or a rate alarm output, of minor variations in
flow rate. As the smoothing factor increases, the rate display gets progressively
more stable. The best advice for the F4 value is to start at 1 and work up until the rate
achieves a happy medium between response and steadiness.
The ratemeter updates every 0.5 seconds. If the input signal goes to the zero rate
value, and if smoothing is used, it may take a number of rate updates before the
displayed rate actually goes to zero. The rate zero timeout is the number of seconds
the Eclipse will wait at the zero rate input value before forcing the displayed rate to go
to zero. If the rate smoothing factor is 1, the rate display will go to zero if the input
goes to the zero rate value for the rate zero time. One second is normally a good
number for the rate zero timeout for flow applications.
The analog input select block tells the Eclipse to use either the 4-20 mA current
signal input terminal or the 0-10V signal input terminal as the input to the counter
and ratemeter.
Column o - other factors
Block
Parameter
Range (Default Value is Bold)
01
Rate Mode Select
0 Square Root Extraction
1 Linearization
02
Cutoff
3.00 - 10.00 mA (F6=0))
0.01-4.00V (F6=1)
4.00
0
03
Constant
0.00001-99999
4.00
04Number of
2-15
points
The flowmeter or flow transmitter output signal varies directly with flow rate. As flow
rate increases, the output signal increases. In some cases, there is a directly pro-
portional relationship between the flow rate and the output signal. This means that
when the flow rate doubles, the output signal doubles; when the flow rate decreases
by say, 70%, the output signal decreases by 70%. A flowmeter output that operates
like this is considered linear. The graph below shows a linear output of 4-20 mA as
the flow rate varies from 0-100 GPM.
