User Manual
E126-P-EG
Page 30
FW_E126-P-EG_M_v0301-01_EN
6
PRESSURE
6.6 CALIB-HIGH
Calibrates the input value for 20 mA. This setting is used because the
signal from the pressure sensor might not be exactly 20.0 mA at maximum
pressure. This function measures the real output value at maximum
pressure.
Make sure the offered signal is correct before calibration takes place
as this has a major effect on the accuracy of the system.
After pressing PROG, three settings can be selected:
●
CALIB: Calibrates the input with the actual 20 mA value. After pressing
enter, CAL SET is displayed as soon as calibration is completed. From
that moment, the analog value must be less than the calibrated value for
a reliable measurement.
●
DEFAULT: Reinstalls the manufacture’s values.
●
CAL SET: Selects the last calibrated value.
5.5.8
MENU 7: FORMULA
7
FORMULA
7.1 EQUATIONS TYPE
Shows the formula. The type EG stands for Equations Gas - flow computer
for corrected gas volume.
The formula used:
Q
normal
= calculated volume at reference conditions
Q
= measured volume
P
= line pressure
P
normal
= reference pressure
T
normal
= reference temperature
T
= line temperature
C
normal
= reference compressibility factor
C
= compressibility factor
7.2 T-NORMAL
(TEMPERATURE)
Enter the reference temperature T
normal
with two decimals in Kelvin (K).
In most applications, the volume is calculated at 0°C, which is 273.15 K.
The temperature compensation is disabled with value zero (0).
7.3 P-NORMAL
(PRESSURE)
Enter the reference pressure P
normal
with three decimals in the selected
pressure unit.
In most applications, the volume is calculated at 1.013 Bar.
The pressure compensation is disabled with value zero (0).
7.4 C-NORMAL
(COMPRESSIBILITY)
Enter the reference compressibility factor C
normal
for the gas at reference
conditions.
The compressibility compensation is disabled with value zero (0).
7.5 COMPRESSIBILITY
Enter the compressibility factor C for the gas at operating conditions. The C
factor indicates how a real gas behaves with respect to an ideal gas (with
C=1), that exactly obeys the ideal gas law (PV/T=nR).
The compressibility compensation is disabled with value zero (0).
5.5.9
MENU 8: ANALOG OUTPUT
An analog 4-20 mA signal is generated according to the flowrate with a 12 bits resolution. The
settings for Flowrate influence the analog output directly and should be configured first. The
relationship between rate and analog output is set with the following functions.
8
ANALOG OUTPUT
8.1 OUTPUT
If the analog output is not used, it can be disabled to minimize power
consumption and save battery life. When the output is disabled, a current of
about 2 mA is generated and the unit can still be supplied from this signal
(provided a power supply is connected).
While powering-up the loop, the initial current is approximately 2 mA.
When the output is enabled, it can take a few seconds before the correct
current is generated.
