Secondary Ignition Pickup (capacitive with BNC)
Due to the high voltages involved in secondary ignition systems, it is not possible to make measurements by direct connection. Attempting to make a direct connection will almost certainly damage the measuring instrument.
The PICO-MI074 is a capacitive pickup that simply connects around the insulation of an ignition circuit component such as a plug wire. This avoids the need for direct connection.
The PICO-MI074 comes with a shielded 1.8 m (6 foot) lead. It is suitable for use with conventional ignition systems and most HEI and DIS systems. Our library of Automotive Waveforms contains example waveforms captured using a PicoScope automotive oscilloscope and the PICO-MI074.
Although ideal for use with a PicoScope automotive oscilloscope, the PICO-MI074 pickup can also be used with most other makes of oscilloscope provided they have a waveform invert option.
How to use the PICO-MI074 Secondary Ignition Pickup
Safety precautions before use:
- Keep the lead away from pulleys and other moving parts
- Keep the lead away from heat
- Never let the pickup come in direct connection with primary or secondary voltage (otherwise the PicoScope may be damaged)
- Always use the ground clip
- Do not let the metal portion of the pickup contact a ground
Connecting the PICO-MI074:
- Connect the PICO-MI074 to the automotive oscilloscope first
- Connect the ground clip to a good ground on the vehicle and check before attaching the clip to a high voltage lead.
- Clip the pickup clamp around the insulation of a secondary coil HT lead or plug wire. Never connect directly!
- Standard Ignition: clip the pickup around the coil wire (or one plug wire at a time)
- Integrated coil: clip the pickup around the central location on the distributor cap
- DIS: clip the pickup around one plug wire at a time
While HT leads would appear to be components from the past, the secondary ignition pickup lead is far from redundant. We have relied on these devices to obtain critical secondary ignition information for years, assisting with diagnosis of misfires and emission failures.
On older vehicles, you can use a PICO-MI074 to monitor the ignition coil output before the distributor which yields a sequential, comparitive view of all cylinders in firing order. Identify cylinders by connecting another scope channel to a cylinder-specific signal to (e.g. an injector or to the CAM sensor) or use another PICO-MI074 on a plug wire. Trigger using that secondary channel.
COP coils are being introduced in many new vehicles. If you wish to conduct hands-free testing of secondary ignition, an inductive COP proble is difficult to use. We suggest using the PICO-MI074 with our PICO-TA037 for hands-free intermittent misfire detection under road-test conditions. These leads allow you to monitor secondary ignition events, so revealing the activity in each cylinder under true operating conditions.
Typical examples of use:
- Confirmation of secondary ignition events
- Can be applied to a variety of HT ignition systems, conventional, wasted spark, COP and cartridge-style ignition.
- Hands-free misfire detection (unlike the COP/Signal probe)
- HT integrity tests
- Confirmation of coil on plug serviceability under load