Siemens SITRANS P500, Руководство по эксплуатации, Страница: 155 / 238

Operate
6.3 Description of the operating functions
SITRANS P500 with HART
Operating Instructions, 12/2014, A5E02344528-09
155
In the calculation example, a number of filled "cans" is set for the output scaling. You can
enter up to five characters for any given unit.
Note
Permissible input values
All alphabetic a...z, A...Z and numeric 0...9 inputs are allowed for the customized unit. The
following characters are also allowed:
° " $ / < > * , _ + - = @
In the calculation example, you have a start of scale value of 0 cans and a full scale value of
1000 cans. At a process pressure of 0.5 bar, you obtain the value 250 cans for the "User"
measuring mode.
See also
"2.1.9 User" (Page 98)
6.3.3 Setting zero point and limit point
You can set the start of measurement and end of measurement using the SIMATIC PDM
software, the local user interface or the HART communicator. You can use this function to
realize rising or falling characteristic curves.
The pressure unit can be set separately for the display and for HART communication.
"1.1.3 Measuring Range" (Page 69)
6.3.4 Flow characteristic
Description
If the measuring mode selector was assigned parameters as "volume flow" or "mass flow",
you can select the characteristic for the output current for the device version "differential
pressure and flow rate" as follows:
● linear "linear": proportional to differential pressure
● square root extracting "srlin": proportional to the flow, linear to the application point and
then according to the root function.
● square root extracting "sroff": 0 to the root application point and then in accordance with
the root function
● square root extracting "srlin2": proportional to flow rate, two-step linear up to the root
application point. The first linear section ranges from the zero point to 0.6% of the output
value and 0.6% of the pressure value. The second linear section runs with a higher
gradient to the root application point and then in accordance with the root function.