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ComBricks User Manual v6.4.0 | January 18| © PROCENTEC 126/219
12.2.4 PA measurements
The PA measurements page shows a static scope image; it is not an actual scope measurement. The blue
arrows illustrate the measured value of the amplitude and the jitter. The values are displayed in the
corresponding boxes (see
Fig. 83 ).
12.2.4.1 Amplitude
The amplitude is the difference between the highest and the lowest measured value of the AC signal (the
actual data). The displayed result is measured by taking samples from all the bits in a telegram. Not the entire
bit is measured, but only a small part to filter out irregularities such as overshoots.
12.2.4.2 Jitter
Jitter is described as ‘Zero -crossing point deviation ’, which means that the changing of a bit does not occur at
the intended time. This is acceptable within the limit of 3200 nanoseconds, positive or negative. Causes for
high jitter times can be wiring mistakes, EMI, cable cross talk or device problems.
12.2.4.3 Polarity
This is NOT the polarity of the bus wiring, but the internal communication signal. In some products it is possible
that the polarity is switched. This does not affect the communication.
12.2.4.4 DC noise
The DC noise indicates how much the voltage of the signal varies. If the noise is too high it can influence the
communication; it should not exceed 100 mV.
Fig. 83 - PA measurements
Measurements
Select the correct slot
and the station address
of the PA slave
Measurements
Measurements