DIS primary ignition 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.

 

WARNING

This test involves measuring a potentially hazardous voltage.

Please ensure you follow manufacturers' safety instructions and working practices and ensure the rated voltage for all accessories you are using meets or exceeds the expected voltage.

 

 

WARNING

Uninsulated HT pickups are designed to clip around double-insulated HT leads only – they are not designed for direct connection to a hazardous live voltage.

To prevent injury or death, when connecting or disconnecting an HT pickup:

  1. switch off the ignition
  2. clean the HT leads
  3. inspect them for damage
  4. clip the HT pickup over the desired undamaged HT lead
  5. ensure all test leads are kept clear of hot or rotating parts before starting the engine

 

How to perform the test

View connection guidance notes.

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.

  1. Ensure the ignition is turned off.
  2. Connect the 10:1 attenuator into 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. Minimise the help page and with the example waveform on your screen PicoScope has already selected suitable scales for you to capture a waveform.
  7. Start the scope to see live data.
  8. With your live waveforms on screen stop the scope.
  9. Stop the engine and ensure the ignition is off.
  10. Use the Waveform Buffer, Zoom and Measuring tools to examine your waveform.

 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.

The blue trace is the Low Tension (LT) signal, measured from the coil's negative terminal (marked number 1). The red trace is the High Tension (HT) output voltage measured at the plug lead.

Both waveforms show exactly the same burn time of 2 milliseconds (ms). A permanent or intermittent loss of the secondary picture is usually due to a failing coil or HT (High Tension) voltage tracking to earth. Losing the primary picture will result in a total loss of HT voltage.

GT392-1

Disclaimer
This help topic is subject to changes without notification. The information within is carefully checked and considered to be correct. This information is an example of our investigations and findings and is not a definitive procedure. Pico Technology accepts no responsibility for inaccuracies. Each vehicle may be different and require unique test settings.

Suitable accessories

  • Secondary ignition pickup (capacitive with BNC)

    £58.00

  • Multimeter Probes

    £6.00

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Guided test: Primary vs Secondary