201
7-0
2
32
Level Probe LGC2
Electrical Connection
6.6
Maximum Load for Device 4 to 20 mA Analog
The maximum load resistance depends on the supply voltage (U) and must be determined
individually for each current loop, see formula and diagrams for device and temperature head
transmitter. The total resistance resulting from the resistances of the connected devices, the
connecting cable and, where applicable, the resistance of the process connection may not
exceed the load resistance value.
Figure 6.3
A
Load diagram of the device for estimating the load resistance. Additional resistances,
such as the resistance of the extension cable, have to be subtracted from the value
calculated as shown in the equation.
B
Load diagram for HUT temperature head transmitter for estimating the load resistance.
Additional resistances must be subtracted from the value calculated as shown in the
equation.
R
Lmax
Max. load resistance [
]
R
add
Additional resistances such as resistance of evaluating device and/or display unit, cable
resistance [
]
U
Supply voltage [V]
L
Basic length of probe connection [m] (cable resistance per wire
0.09
/m)
413
630
195
1065
35
20
25
5 15
847
30
30
20 25
15
8
35
10
1080
880
480
280
680
80
R
Lmax
– 2 x 0.09
x L – R
U – 10.5 V
23 mA
m
– R
U – 8 V
0.025 A
R
Lmax
add
add
10.
R
[ ]
U
[ ]
V
A
B
R
[ ]
U
[ ]
V
Note!
When using the measuring device in hazardous areas, installation must comply with the
corresponding national standards and regulations and the instruction manuals or installation or
control drawings (SI, ZD).
