DKS PD96, Руководство пользователя, Страница: 16 / 57

User manual for meter with U/I input PD96
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Figure 4.13. Serial connection of passive 2-wire sensor with PD96 unit and
other current measurement device (e.g. PLC controller).
If device B (Figure 4.14 , 4.15) is equipped with galvanic separated input or if
different potentials between A and B devices signal grounds are allowed (e.g.
if RS-485 interface is separated or unused), current loop can be closed without
separator
G .
Calculation of maximal allowable resistance of separator´s input
Maximal resistance of the input (RG max.) and wires (RW max.) are calculated for
circuit from Figure 4.15. Used symbols are described below.
U
s min.
- minimal sensor supply voltage (given in technical data of
sensor),
U
g
- voltage drop on galvanic separator input (constant for 4-20 mA
range ofcurrent),
I
max
= 20 mA - maximal current of current loop,
U
0
= 24 V - sensor supply output voltage of device A,
R
0
= 30
Ω
- sensor supply output resistance of device A,
R
INP.
=
50 Ω
- measurement input resistance of device A,