Distributorless Ignition System (DIS) primary vs secondary ignition

The purpose of this test is to investigate the relationship between the primary ignition characteristic and the secondary ignition event within a DIS system.

How to perform the test

View connection guidance notes.

1. Ensure the ignition is turned off.
2. Connect the 10:1 attenuator to PicoScope Channel A.
3. Connect PicoScope Channel A to the ignition coil negative terminal and to earth.
4. Connect a secondary ignition pick up lead to one of the coil HT leads and to PicoScope Channel B. Ensure the ignition pick up lead is also connected to earth.
5. Start and run the engine at idle.
6. Minimize the help page. You will see that PicoScope has displayed an example waveform and is preset to capture your waveform.
7. Start the scope to see live data.
8. With your waveforms on screen stop the scope.
9. Stop the engine and ensure the ignition is off.
10. Use the Waveform Buffer, Zoom and Measurements tools to examine your waveform.

Note 

This helpfile refers to a 10:1 attenuator. If you are using a 20:1 attenuator please adjust the Probe settings for the relevant channel. These settings can be found under the Channel Options button, then: Probe > 20:1 Attenuator.

Note

If a secondary waveform cannot be seen then this could be because the output is positive-fired. If the HT pickup is moved to another HT extension lead, the waveform should then appear.

Alternatively, you can change the settings to look at a positive-fired coil. Select settings for channel B and change the probe from Secondary Ignition Probe (Inverted) to Secondary Ignition Probe (Pos).

Example waveform

Waveform notes

The example waveform shows the close relationship between the ignition's primary circuit and the secondary output. The primary circuit transfers its characteristics into the secondary through mutual inductance, causing the secondary to mirror the primary exactly.

GT392-1