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U408_flowthermNT_B_e_160420
19/35
www.hoentzsch.com
If the working medium density is not known, it can be determined with the formula:
W-density = P / (R * T)
where P = absolute pressure in Pa, R = specified gas constant in J/(kg*K), T = temperature in K.
Here the specified gas constants of some gases:
sample gas
specific gas constant
in J/(kg*K)
sample gas
specific gas constant
in J/(kg*K)
dry air
287
hydrogen H
2
4124
steam H
2
O
462
methane CH
4
518
argon Ar
208
nitrogen N
2
297
carbon dioxide CO
2
189
oxygen O
2
260
carbon monoxide CO
297
propane C
3
H
8
189
helium He
2077
sulphur dioxide SO
2
130
5.3.4
FA – Operating conditions
Menu -> Settings -> Sensor -> FA input -> Operating conditoins
When choosing the relevant units (see 5.3.20.6) service temperature and working pressure are needed for
calculation purposes. The operating conditions can be entered in this menu or determined with connected
sensor.
5.3.4.1
Service temperature
Measured or entered unit in °C
5.3.4.2
Working pressure
Measured or entered unit in hPa
5.3.5
FA – Standard conditions
Menu -> Settings -> Sensor -> FA input -> Standard conditions
Standard conditions for Höntzsch are +21 °C (70 °F) and 1014 hPa (14.7 psia). Any standard can be set
via the standard temperature and standard pressure parameters.
5.3.5.1
Standard temperature
Input value in °C
5.3.5.2
Standard pressure
Input value in hPa
5.3.5.3
Standard density
Input value in kg/m³ depending on set standard conditions for calculating the mass flow rate.
5.3.6
FA - Pairs of values
Menu -> Settings -> Sensor -> FA Input -> Pairs of values
If pairs of values is selected (see 5.3.1.1), then the values stored here for determining the measured
value are applied as a calibration curve.
Selection:
Configuration
= enter the
quantity
of pairs of values (minimum 2, maximum 30)
for processing and display
Pairs of values
= display and amend pairs of values.
A pair of values always consists of a velocity value in m/s
and a frequency value in Hz.
The condition being: the pairs of values must be ever
increasing, i.e. the next velocity and frequency value must always
be greater than the previous one.
