Network Design; Designing A Measuring Network In A Non-Explosive Environment; Power Supply Voltage - +Gf+ 2298 Bedienungsanleitung

Type 2298 80 GHz Radar Level Sensor
4.3

Network Design

4.3.1 Available interfaces
HART® USB modem (e.g. SAT–504)
•
4.3.2

Designing a measuring network in a non-explosive environment

Power supply
Nominal voltage
Maximum voltage (U )
in
Minimum voltage (U )
in
Loop resistance, R
loop
Minimum RA
Maximum RA
RHART resistance for HART® communication
4.3.3

Power supply voltage

Example for calculating the supply voltage:
The required minimum supply voltage at I
U = U + (I * loop resistance) = 11.5 V + (4 mA * 0.25 kΩ) = 12.5 V
supply min. input min. min
The required minimum supply voltage at I
U = U + (I * loop resistance) = 11.5 V + (22 mA * 0.25 kΩ) = 18.5 V
supply min. input min. min
Therefore, in the case of a loop resistance of 250 Ω, the 17 V supply voltage is just sufficient for the whole 4...20 mA in the measure-
ment range.
20
24 V DC
36 V DC
Depends on the load impedance.
(See diagram)
R + R + R
HART cable ammeter
0 Ω
750 Ω
250 Ω (recommended)
= 4 mA:
min
= 22 mA:
max
Pos. Designation
A Minimum voltage at the input terminals of
the device
B Minimum supply voltage (voltage across the
device and the 250 Ω loop resistor)
Instruction manual