Connecting Transducers - HBM SomatXR MX Series User Manual

2 Setting Up a System

2.7 Connecting transducers

Shielding design
Sources of interference can cause electromagnetic fields which can induce
interference voltages inductively or capacitively via the connection cable and device
housing in the measurement circuit and therefore interfere with the device function. It
must be ensured that the devices used in the system also do not transmit any
electromagnetic interferences. Electromagnetic compatibility (EMC), which
encompasses both the required electromagnetic interference immunity (EMI) and the
permissible electromagnetic interference emissions (EME), has become
increasingly important over the years.
According to the HBM Greenline shielding concept, the measuring chain is
completely enclosed by a Faraday cage by appropriate routing of the cable shield.
The cable shield is extensively connected with the transducer housing and is routed
via the conductive plug to the amplifier housing. The influence of electromagnetic
interferences is significantly reduced by these measures.
NOTE
All parts of the measurement chain (including all cable connection points such as
plugs and couplings) must be surrounded by a closed EMC‐ proof shield. Shield
junctions must represent a full contact, closed and low‐ impedance connection.
This is the case for original HBM plug connections.
Ground connection and grounding
As the signal ground and shielding are separated in EMC‐ compliant cabling, the
shielding can be connected at more than one point to the ground, i.e. via the
transducer (metal housing) and the amplifier (housing is connected to the earth
conductor).
If there are differences in potential in the measuring system, a potential
compensating line must be laid (reference value: Highly flexible stranded wire, wire
2
cross section 10 mm ). Signal and data leads must be set up physically separated
from current‐ carrying power lines. Ideally, cable ducts made of sheet metal with an
internal partition should be used. Signal ground, earth and shielding must be laid out
as separated as possible.
In order to minimize the influence of electromagnetic interferences and differences in
potential, the signal ground and earth (or shielding) are designed to be physically
separate in the HBM devices. The mains earth connector or a separate earth
potential lead should serve as the earth connection as is the case for example
regarding potential compensation in buildings. The earth cable should not be
connected to a radiator body, water pipe or similar objects.
Active transducer connection
Some modules can supply active transducers with a supply voltage of 5-24 volts.
MX Modules A4089-5.0 en HBM:Public. 29