Shielding
Interference on the sensor signal can be introduced in various ways.
- through galvanic coupling (common electrical conductors, e.g. common ground or earthing)
- by capacitive coupling (e.g. from the sensor housing to the strain gauge)
- inductive coupling (e.g. interference in connection cables from motors, frequency converters, power electronics)
- due to high-frequency radiation (e.g. from radio devices, Bluetooth, WiFi)
These interferences can be minimized through shielding, the correct earthing concept and correct earthing.
Definition of “earth” and “earthing”
Earth or “GND” or “ground” refers to the electrical line that is usually assigned the potential 0 volts and forms the reference potential for signal and operating voltages. If the “ground” is connected to the potential of the earth via the so-called protective conductor, this is referred to as earthing.
An important requirement for the earth is the ability to conduct large currents and not to form a potential. In practice, this is not the case, so it is important to have the right “earthing concept” to minimize interference.
Types of “ground”
Signal ground
A generally large-area, low-impedance trace or surface within an electronic circuit to which all signals are referenced.
Housing ground
Usually the metal housing of an electronic device, which is also usually connected to earth with a low resistance to protect people.
Star structure
If the earth connections of all components of a measuring chain converge at one point, this is referred to as a star structure. As all impedances between the 1...n stages of the measuring chain are 0, no interference can be coupled in.
