Fluidwell F013-A, Manual

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Page 16
FW-F013-A-M_v0404_01_EN.docx
3.3.7 EXPLANATION OF SETUP-MENU 6 - FLOWMETER
SETUP FUNCTIONS AND VARIABLES
6 FLOWMETER
6.1 FORMULA
The F013-A can process the (0)4-20mA signal in two ways:
▪
Interpolation: the signal is processed linear
R = S x I
▪
Square root: for differential pressure
R = S
√
I
where R = the calculated flow rate, S = the maximum flow rate at
20mA (span is programmed with SETUP 1.3/1.4 and 2.4/2.5) and I =
the scaled analog input value between 0 (zero) for (0)4mA and 1
(one) for 20mA.
6.2 FILTER
The analog output signal of a flowmeter mirrors the actual flow. This
signal is measured several times per second by the F013-A. The
value measured is a "snap-shot" of the real flow as it will be
fluctuating. With the help of this digital filter a stable and accurate
reading can be obtained. The filter level can be set to a desired value.
The filter is based on three input values: the filter level (01-99), the
last measured analog value and the last average value. The higher
the filter level, the longer the response time on a value change will be.
Below, several filter levels with response times are indicated:
Filter value Response time to step change in analog input value (seconds)
50% 75% 90% 99%
01 filter disabled filter disabled filter disabled filter disabled
02 0.3 0.5 1.0 1.8
03 0.5 1.0 1.5 3.0
05 1.0 1.8 2.8 5.3
10 1.8 3.5 5.6 11
20 3.5 7.0 11 23
30 5.3 10 17 34
50 8.8 17 29 57
75 13 26 43 86
99 17 34 57 114
6.3 CUT-OFF
To ignore small flows e.g. leakage or vibration, a low-flow cut-off can
be set as percentage of the full range of 16mA (or 20mA). When the
analog value is less than required with this setting, the signal will be
ignored. The cut-off value can be programmed in the range 0.0 -
99.9%. Below two examples are given.
Formula (SETUP 6.1)
Span
(SETUP
1.3/2.4)
Required
cut-off
Cut-off (SETUP 6.3) Required output
Interpolation 450 L/min 25 L/min (25/450)*100%=5.5% 16mA*5.5%+4mA=4.88mA
Square root 450 L/min 25 L/min (25/450)
2
*100%=0.3% 16mA*0.3%+4mA=4.05mA
6.4 TUNE MIN / 4mA
With this setting it is possible to calibrate the input value for (0)4mA
as the signal from the flowmeter might not be exact 4.0mA (or 0.0
mA) at flow rate zero. This function will measure the real output value
at flow zero.
The input loop powered version - type A-PL - requires a signal of at
least 4mA; not lower!
Please make sure that the offered signal is correct before calibration
is executed, as this has major influence on the accuracy of the system