Lesson 3/Learning Event 4
RPM Measurement
FIGURE 63. RPM.
Setting the TEST SELECT switches to the required test number tells the VTM to make an RPM
measurement when the TEST button is pressed and released.
On CI engines, the VTM measures the time needed for an engine revolution.
On SI engines, the VTM measures the time between cylinder firings.
The VTM uses an internal clock as a time reference to convert these measurements to RPM.
The VTM displays the engine speed in RPM.
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