FW_F126PEGTP_v1901_04_EN.docx
Page 15
3.1.9.
EXPLANATION OF SETUP MENU 8 - FORMULA
EQUATIONS TYPE
81
This setting shows the formula. The type EG stands for Equations Gas -
flow computer for corrected gas volume.
The formula used:
Q
normal
= Q * (P/P
normal
) * (T
normal
/T) * (C
normal
/C)
Q
normal
= calculated volume at normal conditions
Q
= measured volume
P
= line pressure
P
normal
= normal pressure
T
normal
= normal temperature
T
= line temperature
C
normal
= normal compressibility factor
C
= compressibility
T-NORMAL
(TEMPERATURE)
82
Program here the reference temperature T
normal
in degrees Kelvin (K).
In most applications, the gas volume is calculated at 0°C which is
273,15K.
P-NORMAL
(PRESSURE)
83
Program here the reference pressure P
normal
in the selected pressure unit.
In most applications, the volume is calculated at 1.013 Bar.
C- NORMAL
(COMPRESSABILITY
FACTOR)
84
Program here the compressibility factor for the gas at
reference
conditions. With the value of 0, the C
normal
is disabled.
COMPRESSABILITY
FACTOR
85
Program here the compressibility factor for the gas at
operating
conditions.
The C factor indicates how a “real” gas behaves with respect
to an
“ideal” gas which exactly obeys the “general gas law”
(PxV/T=constant) where the compressibility factor (C) is 1.
With the value of 0, the compressibility factor is disabled.
3.1.9.
EXPLANATION OF SETUP MENU 9 - ANALOG
A linear 4-20mA signal (option AB: 0-20mA or option AU: 0-10V) output signal is generated that
represents the flowrate. The settings for the flow rate influence the analog output directly. The
relationship between the flow rate and the analog output is set with the following settings.
OUTPUT
91
If the analog output is not used, select disable to minimize the power
consumption (e.g. save battery life-time).
Option AP: When a power supply is available but the output is disabled, a
3.5mA signal will be generated.
RATE-MIN
92
Enter here the flow rate at which the output should generate the minimum
signal (0)4mA or 0V - in most applications at zero flow. The number of
decimals shown depend upon setup 23. The engineering units/time (e.g.
L/min) are dependent upon setup 21 and 22.
RATE-MAX
93
Enter here the flow rate at which the output should generate the maximum
signal (20mA or 10V) - in most applications at maximum flow. The number
of decimals shown depend upon setup 23. The engineering units/time (e.g.
L/min) are dependent upon setup 21 and 22.
CUT-OFF
94
To ignore leakage of the flow for example, a low flow cut-off can be set as
a percentage of the full range of 16mA, 20mA or 10V.
When the flow is less than the required rate, the current will be the
minimum signal (0)4mA or 0V.
Example:
Calculate the cut-off.
Rate-min: 0L/min [4mA], Rate-max: 100 L/min [16mA], Cut-off: 2%
Required rate [L/min]:
(rate-max - rate-min)*cut-off: (100-0)*2%=2.0L/min
Output [mA]:
rate-min + (rate-max*cut-off): 4+(16*2%)=4.32mA
