Have you tried scoping them previously and are not content with the patterns captured?
Are you scoping to learn or to diagnose, in other words: Is this car broke?
Are you looking to scope voltage or current?
All the piezo's I've seen are switched both on power and control sides and you will most likely wish to be on both sides. Ground both channels to the driver module's ground or to battery ground and then probe each ckt as you would any other high voltage fuel injector ckt (GDI or Diesel).
The following capture was taken with the ground reference on the "Other" injector wire, as opposed to battery or chassis ground. The waveform makes more sense taken that way.
Just wanted to tell you a better and safer way to do this. You are always taking a risk when you place the scope ground on a voltage source. Besides being at risk for creating a ground loop, you can risk damage from high voltages. This is especially true when working with injectors that may have a high voltage kick. Even with attenuators in place, they don’t function as intended when the scope is not grounded.
Here is the safe way to do it:
Use two channels, both grounded to bat neg. One on each side of the injector. Now deploy a math channel like A-B. The math channel will display what you want (injector voltage drop) and you will still have two more channels you can use safely
_________________
Tom Roberts
(The Picotologist) http://www.autonerdz.com
skype: autonerdz
THE PicoScope Automotive Authority
In North America
Use two channels, both grounded to bat neg. One on each side of the injector. Now deploy a math channel like A-B. The math channel will display what you want (injector voltage drop) and you will still have two more channels you can use safely
I agree that there is some inherent risk with the method I suggested, mainly due to the "ground loop" as you call it. When deploying multi channels, it is vital to consider where the ground connection is made & what it is shared with.
However, for the purpose of the capture I displayed, I don't think that my method is unsafe.
It would not be wise to do it the 'unsafe' way, especially when there is a high voltage kick. As I mentioned, the attenuator needs to be grounded to do its job and protect the scope and allow you to scale the high voltage.
When you have the scope ground on a voltage supply, you cannot ground the scope.
Therefore it would be impossible to show the safe method on two channels and the unsafe method on the other two since the scope must be grounded.
Frankly, I would not want to look at anything with a high voltage kick and have the scope ground attached to the device rather than ground. This puts the scope and the PC at risk of high voltage kick.
You can get away with doing that with low voltage stuff using one channel only. One example might be placing signal and ground for one channel across a floating ground VRS crank sensor, such as on a Ford EDIS system, so you can measure true peak to peak amplitude. With math channels though, it's really not necessary.
Bottom line.....Unless you are really confident in what you are doing, never place the scope ground on a voltage source.
_________________
Tom Roberts
(The Picotologist) http://www.autonerdz.com
skype: autonerdz
THE PicoScope Automotive Authority
In North America
Here are some images of a negatively controlled gasoline injector form a Toyota done different ways. I was using a 4423 scope so could do this without the need for an attenuator and with no risk to the scope.