The purpose of this test is to investigate the relationship between the primary ignition characteristic and the secondary ignition event within a DIS system.
Connection for diagnostic work will vary dependent on application.
Technicians should whenever possible gain access to the test circuit without damage to seals and insulation. If this is not possible then make sure appropriate repairs are completed.
General connection advice
PicoScope offers a range of options within the test kits.
Dependent on difficulty of access, choose from:
Testing sensors and actuators (to include relevant circuit/connectors):
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.
Uninsulated HT pickups are designed to clip around double-insulated HT cables only – they are not designed for direct connection to a hazardous live voltage. To prevent injury or death, switch off the engine and secure against restart. Clean and inspect the HT lead for damage to insulation and fit only to undamaged fully insulated leads. Ensure that leads are safely clear of hot and / or rotating parts. The engine can now be restarted for the test duration.
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.
Use the Waveform Buffer, Zoom and Measuring tools to examine your waveform.
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).
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.
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.
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