Measuring Mode Selector; Variable Mapper - Siemens SITRANS P DS III Operating Instructions Manual

The following device variables are activated only when the allocated measuring mode is
activated and parameterized simultaneously:
● "Level", "Volume" and "Mass" are allocated to the "Level" measuring mode.
● "Volumetric flow" and "Mass flow rate" are classified as "Flow rate" measuring mode.
● "User" is allocated to the "User" measuring mode.
The inactive device variables have the CONSTANT status.
7.3.2

Measuring mode selector

You can use this switch to toggle between measuring modes "Pressure", "Level", "Flow rate"
and a characteristic curve programmable by a "User".
If a measuring mode has been selected using the measuring mode selector, it has to be
configured. This does not mean that this block has an automatic effect on the current output
(4 to 20 mA). For that, you need to switch the corresponding device variable to the primary
variable (PV) using a so-called variable mapper.
7.3.3

Variable mapper

Introduction
In this transmitter, the dynamic variable that determines the behavior of current output is
always called the primary variable (PV). You need to use the variable mapper for a number
of purposes, including selecting which device variable is to be switched to PV. The variable
selected as PV using a PC program such as SIMATIC PDM or using the HART
Communicator is scaled once again in the analog output stage to a zero value and a limit
value. These two values then correspond to the current values 4 and 20 mA.
As soon as the PV is switched over using the variable mapper, the start of scale value and
full scale value in the analog output stage are preset to the limit values of the new device
variables. You can define these limit values within the individual block functions.
The dynamic variables "Primary", "Secondary", "Tertiary" and "Quarternary" (PV, SV, TV,
QV) can be interconnected with any active device variables. Various different measuring
mode examples are conceivable with a 4 bar pressure transmitter.
See also
Measured value status (Page 116)
SITRANS P DS III with HART
Operating Instructions, 06/2013, A5E00047092-09
Operating functions through HART
7.3 Selecting the measuring modes
107