Before capturing a new set of data, prepare the intended operating conditions (FO, misalignment) and allow
power transfer to be established, then click the start button.
The GUI will then begin to periodically log the operating conditions and the logged data will be shown in a table in
the middle of the GUI window. We recommend recording data for the whole load range in appropriate steps. It is
also recommended to record at least three data points for each load, as the operating parameters may vary
slightly – mostly because of noise.
Figure 29. Logged data
One of the variables used to estimate foreign object presence is received power, reported by the RX via received
power packet (labelled RxPwr in the table). This packet is usually only sent once every 1500 ms. It is therefore
necessary to wait for about 1.5 seconds after changing the load to allow the RPP value to be updated before
reading. We recommend using the following procedure:
1. Record a few samples on the first load step.
2. Pause the recording, change the load and wait at least 1.5 s.
3. Optional: check if the recorded samples are all acceptable.
4. Resume the recording.
5. Repeat until enough load steps are recorded.
Data points containing the old RPP value can be distinguished by comparing both the RxPwr and Icur values to
the previous points. If a sample contains an RPP value similar to a previous point (load step), but the current is
significantly different, it is most likely caused by desynchronization of the current and the received power reading.
The desynchronized data points can also be spotted in the plot, as those points will usually be significantly higher/
lower than the rest.
Any unsuitable data point can be deleted using the “X” button in the Action column.
UM3161
Foreign object detection (FOD)
UM3161 - Rev 1
page 24/78
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