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Measuring secondary ignition waveforms
A number of automotive users have asked about optimising the oscilloscope settings for measuring secondary ignition waveforms and in particular ensuring that peak kV is measured correctly.
Ignition waveforms can be difficult to capture as the event occurs over a relatively long period of time, yet contains a spike (plug kV) of very short duration. This combination requires both a high sampling rate and a large buffer memory.
The first step is to ensure you are using PicoScope R5.09.4 or later (in PicoScope select Help | About to check the release number). If you need to upgrade, this can be done free of charge from the website. Downloading the standard version of PicoScope will not remove the automotive features from the automotive software.
Most users will start from the Automotive drop down menu — this gives an acceptable waveform in most cases. If however you lengthen the timebase to view multiple ignition waveforms, then the peak kV spikes may not be displayed reliably. This problem can be solved by increasing the number of samples captured. To do this select Setting | Options and click on the "Advanced" button. Next change the maximum number of samples to 32,000 for the ADC-212/3. Click on OK twice to complete the changes.
To save the settings for future use, either select File | Save Settings, or save a reference waveform using File | Save As.
Article: KB-174
15 Jun 2007
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