<short-inter-supp-lab-test>
When performing short-distance interference tests in laboratories, the output interferences of a component are investigated.
The following specifications can be made for laboratory tests.
 
Measuring method
The measuring method describes the measuring equipment applied to the DUT regarding its interference emission. There are two typical measuring methods:
1.
 
Measurements of conduction-guided interference voltages on the artificial network
This measuring method is applied at those vehicle components which emit the major part of the interference energy via the power supply conductions (e.g., radiator fan, interior ventilation, fuel pumps and vehicle generators).
2.
 
Measurement of interferences by radiation in the TEM cell
 
Measuring equipment
At this place, the used measuring equipment can be described. Typical measuring equipment are, e.g., measuring receiver and spectrum analyser. The exact documentation of the setting of the measuring equipment should be made after the test set-up.
 
Measuring band width
1.
 
Wide-band interference
A wide-band interference is a band width of an interference signal which is equal to or bigger than the chosen measuring band width of the interference measuring receiver.
2.
 
Narrow-band interference
A narrow-band interference is a band width of an interference signal which is smaller than the chosen measuring band width of the interference measuring receiver.
 
Frequency band
The frequency band can be designated here (e.g. long wave, medium wave, short wave, L, M, ...)
 
Frequency range
Specification of the frequency range.
 
Interference suppression level
The interference suppression level defines a value for the maximum interference voltage (see (Interference suppression levels)).
 
Operating state
The operating state defines the state of the system at which the test is performed. If the test is to be performed with various operating states, these can be grouped.
 
Additional specifications
Apart from the a.m. specifications, it is always possible to give additional specifications for a test.
Figure 52: Structure of a laboratory test
Example for content:
The following table shows an example for the description of the narrow-band interference. The values have partially been taken from [(Interference suppression levels);DIN 57 879;;Part 3;].

Examples for interference suppression levels for measurements on the artificial vehicle network
Measuring method
Measuring bandwidth
Radio frequency band
Interference suppression level
Operating states
 
Artificial network
Broadband
LW
5
Idle running
Full load
 
Artificial network
Broadband
MW
KW
4
Idle running
Full load
 
Artificial network
Broadband
UKW
3
Idle running
Full load
 
Structure of the measuring method
Example for content:
Measuring method: Artificial network
Measuring device: Artificial network
Additional specifications for the measuring device:
Assembly and ground arrangement in the vehicle have to be simulated.
The maximum interference voltage has to be identified by modifying load and the number of revolutions.
Figure 53: Measuring set-up for measuring a consumer
1. Voltage supply
2. Artificial network; casing electrically connected to part 5
3. Interference measuring receiver; 50 W - Direct impedance
4. Measuring object in mounting position
5. Sheet metal plate; minimum dimensions (width*height in mm): 1000*400
Thickness (in mm): 1.0 (+/- 0.2)