Analog Output - Siemens SITRANS P DS III Operating Instructions Manual

Operating functions through HART
7.3 Selecting the measuring modes
7.3.10

Analog output

Introduction
The "Analog output" block converts the value provided by the dynamic primary variable (PV)
into a current value of 4 to 20 mA. When you actuate the measuring mode selector, you
automatically define the start of scale value and the full scale value to the current values 4
and 20 mA, respectively. Limit values of corresponding device variables are used for scaling
the analog output by default. You have entered these limits when setting the parameters of
your measuring mode.
Example for measuring mode "Level"
This means that for a "Level" device variable as PV, 10 m corresponds to the value for 4 mA
and 20 m corresponds to the value for 20 mA. You can change this presetting again in the
"Analog output" block. This is done by restricting the range of the "Level" device variable for
scaling the output current to e.g. 12 to 18 m. This downscaling has no effect on the previous
block scaling. In this case, a current of 4 mA is output for a measured height of 12 m, and a
current of 20 mA for 18 m.
DV Device variable
PV Primary variable
SV Secondary variable
TV Tertiary variable
QV Quarternary variable
Figure 7-9 "Analog output" scaling
120
MA Start of scale value
ME Full scale value
Operating Instructions, 06/2013, A5E00047092-09
SITRANS P DS III with HART