EMC Basics
Results of Disturbance to an Industrial Application Degree of effect The effects of undesired voltage and current in industrial applications range from acceptable functional degradation, to unacceptable functionality failures right up to total function failures of individual components or a complete application These effects are categorized according to degrees: Degree of effect
Description
Example
Function degradation A non-significant influence in the functionality that is accepted as being permissible
Minor measurement imprecision is caused by disturbances that occur on a signal wire. These lie within the defined tolerance.
Function fault
The function is influenced to an impermissible degree which ends with a dying out of the amount of disturbance.
An incremental encoder for path measurement is connected with a PLC counter module. A short circuit in a motor supply wire running in parallel is causing a inductive coupling disturbance and is interfering with the useful signals on the wires for the incremental encoder, which is in turn being interpreted as counter pulses by the following circuit. This causes certain machine functions to be executed at the wrong times.
Function failure
An impermissible influence on the function that can only be resolved by technical measures (e.g. repair, exchange)
During a service call, an electrostatically charged technician comes into contact with a module. An electrostatic discharge occurs which damages or destroys components.
Other examples More examples for the effects of disturbance in a system: Individual impulse, i.e. pulse formed over-voltage caused e.g. by switching an inductive consumer such as a motor or valve. These interfere with the functionality of digital systems by setting or clearing registers if the interference threshold of the device is exceeded. A building only has one external lightning rod and no protection against lightning inside. When lightning strikes, some of the discharge flows into the building and damages electronic circuits.
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