Siemens SITRANS P500, Руководство по эксплуатации, Страница: 151 / 238

Operate
6.3 Description of the operating functions
SITRANS P500 with HART
Operating Instructions, 12/2014, A5E02344528-09
151
Example
The "measuring range limits" specify the pressure range of 0 to 2 bar, which is interpreted by
the following root extraction function as 0 and 100 %. In the following diagram, a process
pressure of 0.5 bar is assumed.
In the "volume flow" measuring mode, a square-root extraction characteristic "srlin2" with a
root application point of 10 % is applied as standard.
In the calculation example, the input value for the "square root extracting function" is
approximately 25% at a process pressure of 0.5 bar. The output value is approximately 50%.
MA Start of scale value p Pressure
ME Full scale value VF Volume flow
Figure 6-11 Calculation of the volume flow
In the calculation example, the two value pairs 0 %;0 % and 100 %;50 % are assigned as
parameters to the "correction characteristic". This setting corresponds to a bisection of the
input value for all output values.
Provide the "volume flow" measuring mode with a volume flow unit chosen by yourself and
the measuring range limits for the volume flow process variable. In the calculation example,
0 l/s and 1000 l/s are taken as the lower and upper measuring range limits. The volume of
flow is thus 250 l/s at a process pressure of 0.5 bar.
See also
"2.1.4 Volume Flow" (Page 86)
6.3.2.7 "Mass flow" measurement type
Description
If parameters are to be assigned to the "mass flow" measuring mode, you can select the
"flow characteristic". The "flow characteristic" can additionally be modified with a "correction
characteristic" e.g. for an orifice.
There is also the option of measuring the mass flow bidirectionally.
See "2.1.5.1 Bidirectional Flow Activation" (Page 90)