Engine RPM
for iPhone
- Engine RPM is an iPhone app that offers a real-time display of the RPM of any engine based on the sound that engine makes. The RPM range is 500-90,000 RPM. You can find it by following this link to the iTunes App Store.
Here
is what display looks like. At the top in large digits is the
calculated RPM. This value updates every 3/4 of a second.
The RPM value is calculated from the peaks in the frequency spectrum
(the graph shown in green).
- Below that
are the hint controls, which specify the RPM range. By
restricting the search to a specific range of values, it is more
likely that the true engine sound can be found from amidst the
background noise. The hint is specified by a center value and a
tolerance value in percent. By swiping left or right in the
blue bands below the hint, you can adjust both the center RPM value
and the tolerance.
- Instead of
a fixed hint band, you can also use tracking mode, which can
track RPM changes over the entire 500-90,000 RPM range. In that
mode the hint controls are replaced by a control that lets you force
the tracked RPM to be close the actual RPM so that true tracking can begin.
- Below the
hint controls is a graph of the frequency spectrum. This allows
you to see the frequency spectrum of the sound produced by the
engine, and thus verify the reliability of the displayed RPM.
The vertical red lines in the spectrum graph correspond to the
harmonics of the fundamental frequency produced by the engine.
If those red lines line up well with the peaks in the frequency
spectrum, then you can rely on the displayed RPM value.
- The
conversion from audio frequency to RPM depends on the engine
configuration. You can choose from a number of built-in
configurations, including 4-cycle and 2-cycle engines. You can
also specify a generic ratio that can compensate for any gear ratio
between the engine and the shaft whose RPM you wish to display.
- Besides
this view, there are two setup/configuration pages. Each page
has it own context-senstive help, which gives more information on how
to use the app. There is also a detailed Operations
manual that can be downloaded from here.
- If you have any questions about this app, you can e-mail us at: info@tunelab-world.com
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