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8
Metrological Features
142
8.4.1.1 Gas pressure - measured or fixed value
By default, the measured value of the gas pressure p in the pipeline by the pressure sensor is
used to calculate C. In some special cases, instead of the measured pressure value, the value
entered into the device as a constant when configuring the device can be used for the calculation.
Then we talk about a substitute or constant value of pressure.
Substitute pressure value ps
This value is used automatically instead of the measured value of gas pressure if the so-called
error conditions occur, i.e. in the following cases:
 the measured gas pressure is outside the measuring range, or
 an error has occurred and the measured gas pressure value is not available:
Constant pressure value p
The constant pressure value is used if the device is not equipped with a gas pressure transducer.
The use of a constant value must be set manually in the device parameters.
Setting of substitute and constant pressure value
The substitute pressure value ps and the constant pressure value p are in fact the only common
value entered in the instrument parameters. If it is to be used as a constant value, it is necessary
to select a constant value for the pressure parameter on the parameter card C instead of the
measured value P. The size of the spare, resp. constant pressure is entered in the field "Spare
const.value". The set value should be as close as possible to the real value of the gas pressure in
the pipeline.
Fig. 69 Setting the replacement pressure value (Compass SW)