VEGA VEGASON 51K…53K - Manual (Page 16)

16 VEGASON 51K … 53K
Types and versions
Several sensors on a voltage source
All sensors are dispatched with the same
communication address zero. If several sen-
sors are operated on one voltage source, a
communication on the signal line with the PC
or with the HART
® -handheld is no longer
possible, as in this case all sensors are ad-
dressed digitally at the same time.
To avoid this, 250
Ω
… 350
Ω
resistors must
be connected directly on the voltage source
in the sensor supply line. The inner resist-
ance of the voltage source must be very
small. The digital communication signal (PC
or HART
® -handheld) used on the sensor line,
is then no longer transmitted to the other
sensors. You can then communicate with the
PC or HART
® -handheld on the signal line of
the appropriate sensor without the participa-
tion of all other sensors in the communication
even though all sensors react to the address
zero. The low inner resistor (alternating load
resistor by filter capacitor) of the voltage
source short-circuits the signals before they
can cross over to the other sensor lines. The
C
R = 0…2
Ω
250 Ω
250
Ω
250
Ω
250 Ω
250 Ω
250 Ω
resistors avoid the adjustment signals of the
actually operated sensor from also being
short-circuited.
With the PC and the adjustment software
VEGA Visual Operating (VVO) or with the
HART
® -handheld, the sensors can be ad-
justed from the address zero to the address
1 … 15. If a sensor is adjusted to the ad-
dress 1 … 15, the sensor no longer delivers
a 4 … 20 mA-signal, but is frozen to 4 mA
(power supply). Nevertheless, the sensor will
continue to provide the measured value digit-
ally. This mode is called multidrop operation.