Primary (current)

The purpose of this test is to examine the primary current characteristics on an external coil type ignition system.

How to perform the test

View connection guidance notes.

  1. Connect a low amp clamp to PicoScope channel A.
  2. Select the 20 A scale and zero the clamp before clamping around the ignition coil negative lead.
  3. Start the engine and allow it to idle.
  4. Minimize the help page. You will see that PicoScope has displayed an example waveform and is preset to capture your waveform.
  5. Start the scope to see live data.
  6. With your waveform on screen stop the scope.
  7. Stop the engine and turn off the ignition.
  8. Use the Waveform Buffer, Zoom and Measurements tools to examine your waveform.

Note

The orientation of the current clamp relative to the wire will determine whether it has a positive or negative output. If a live waveform does not appear on your screen, or appears to be inverted, try reversing the orientation of the clamp.

Example waveform

Waveform notes

This known good waveform has the following characteristics:

You will see 0 A until the primary circuit is switched on. Current then flows and the value rises to around 7 A. The primary circuit is switched off after 1.6 ms at which point the current ceases to flow and the waveform once again reads 0 A.

Waveform Library

Go to the drop-down menu bar at the lower left corner of the Waveform Library window and select, Distributor ignition primary current

Further guidance

GT387-1

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

  • 20 A / 60 A DC (low amps) current clamp

    £111.00

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Guided test: Primary Current