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Chapter 4
Measurement Definition
140
Order Phase
The order phase is measured from the trigger edge to the maximum/positive
signal peak, which is known as phase lag convention.
In the following illustration where the pulse represents the tacho signal and the
sine-wave the signal:
• A negative or falling edge trigger results in a phase angle of 60°
• A positive or rising edge trigger results in a phase angle of 90
In order configurations that are integrating, the reported phase angle reflects
that integration, for example, velocity lags acceleration by 90° and
displacement lags acceleration by 180°.
Influence of Sample Rate and Tracking Filter Definition Settings
The Tracking filter definition is specified in terms of a number of revolutions
(for the measurement). The higher the number of revolutions configured:
• The sharper the tracking filter
• The more accurate/stable the assessment
• The longer the measurement acquisition time
Accuracy and stability also improve when more samples are being considered
and so are sensitive not only to the Tracking Filter Definition but also to the
ADC FMAX setting. The higher the FMAX, the better.
The filter response is similar to one FFT bin (rectangular/no windowing). So
for a more objective benchmark a similar FFT case can be considered such as a
200 line FFT, based on 512 samples.
Rockwell Automation Publication 1444-UM001D-EN-P - June 2018
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