• If the labscope being used has an adjustable Sample Rate, use the faster setting. The control for sample rate speed may be called acquire or acquisition.

• Fast sample rate is important when testing any signal that has a spike associated with it, such as secondary ignition, fuel injectors, and alternator ripple voltage (when a problem exists).

• Use the manual or normal trigger setting rather than AUTOmatic setting if possible.

• When triggering on the firing line, position the trigger voltage level so that it is always higher than the highest point of the spark line.

• When testing a Distributor Ignition System it is possible to view a parade pattern as well as individual cylinders.

- PARADE – Set the time/div to 10 ms.
This setting will allow sufficient time across the display to show all the cylinders in a parade pattern, if necessary raise the RPM enough to have all cylinders showing on the display screen.
- INDIVIDUAL CYLINDERS – Set the time/div to .2 ms or .5 ms.
These settings will allow only enough time to display the event being triggered.
Move the trigger pickup lead to each ignition wire one-at-a-time to see each individual cylinder.
- If the Secondary Ignition waveform appears upside down –
Activate the labscope INVERT feature or reverse the capacitive test lead connections at the labscope.

• When testing an ignition system that uses one coil to fire two plugs the technician can connect a single ignition test lead clip to one ignition wire-at-a-time and diagnose each individual cylinder, no trigger pick-up lead is used.

- Because of the polarity issues involved in this type of secondary ignition system, half of the wires will show upside-down waveforms. Activate the labscope INVERT feature or reverse the capacitive test lead connections at the labscope to have the up-side down waveforms appear right side up.
- Look for spark line duration to be a minimum of 1 mS.
- Spark line must not drop to ground.