Shortening And Extending The Cable; Emc Protection - HBK HBM RTN Montageanleitung

Junction box (e.g. "VKK..." or "VKEX" from HBM)
Fig. 5.3 Parallel connection of several transducers
5.4

Shortening and extending the cable

Use only shielded, low-capacitance measurement cables for extending the cable, making
sure there is a proper connection with minimal contact resistance.
To achieve full accuracy, a 6-wire configuration should be used to extend the cable all the
way to the subsequent electronics.
A 4-wire configuration is used for the load cells and the cable must not be shortened.
5.5

EMC protection

CAUTION
Electrical and magnetic fields often induce interference voltages in the measuring circuit.
To ensure reliable measurement, however, the transducer must be able to transmit signal
differences of a few μV to the analysis unit without interference.
Planning the shielding design
Due to the numerous application options and differing local constraints, we can only
provide you with general information on correct connection. The shielding design suitable
for your application must be planned locally by an appropriate specialist.
HBM load cells with shielded, round cables are EMC-tested in accordance with the
EU Directive and bear the CE mark. Voltage surges as per EN 61000-4-5 can give rise to
deviations from the load cell's specified accuracy. These surges in plants are caused by
lightning strikes or switching operations in power circuits, for example, and disappear
again when interference is no longer active. This is particularly evident with cables over
12
Bridge excitation voltage (+)
(black)
Sensing element (+)
Bridge excitation voltage (-)
(blue)
Sensing element (-)
(red)
Signal (+)
(white)
Signal (-)
(yellow)
Shield
Extension cable
ELECTRICAL CONNECTION
RTN