Primary current

The purpose of this test is to examine the primary current within a Coil on Plug circuit when the COP unit’s primary coil is driven by an external amplifier or control module.

How to perform the test

View connection guidance notes.

1. Connect the 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 waveforms 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.

Notes

The orientation of the amp 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:

• When the circuit is off, the current is at 0 A.
• When the circuit is switched on, the circuit current increases over a period of time up to around 5.6 A.
• The current remains at its 5.6 A peak for around 2.25 s, until the circuit is switched off.
• The current immediately drops back to 0 A when the circuit is switched off.

Waveform Library

Go to the drop-down menu bar at the lower left corner of the Waveform Library window and select Primary current.

GT045-EN