HBM SD01A Bedienungsanleitung Seite 19

SD01A
In certain cases this inductance behavior limits the cable length more severely
than is desirable, since only load cells of the RTN series have such a high
inductance.
For all other types of load celles the applicable computation is as in Table 5.9 .
Max. perm. inductance Lo (μH)
Transducer inductance Li (μH)
Max. cable inductance (μH)
Cable inductance (μH/m)
Max. cable length (m)
Tab 5.9: Maximum cable lengths (considering inductance) for HBM transducers
according to Certificate PTB01ATEX2208 or PTB01ATEX2209
Cable lengths greater than 500m are not specified, basically for the sake of
correct functioning of HBM measuring instruments, therefore greater values
have been correspondingly limited by computation.
As cable capacitance, the wire-shield capacitance (130pF) is taken into
consideration as a parallel connection (all 6 wires) (130pF x 6 = 780 pF). The
wire-wire capacitance is significantly lower and is therefore ignored.
The following considerations are based on the computation of the L/R ratio:
Uo = maximum voltage between 2 conductors = 17.4 V
Ri = minimum internal resistance of the supply = 2*(98 Ohm||352.8 Ohm ||
352.8 Ohm) = 126 Ohm
Li = maximum inductance through the connection clamps of the load cell =
100 H
μ
The computation is carried out according to Recommendation EN60079−11 :
2007, paragraph 6.3.3
A1045−2.4 en/de/fr
Group
19
IIC
200
24
176
0.44
400
HBM