Ignition Probe Discussions \ Tests & Debates - Do YOU need to buy one?

With an inductive probe if you turn the sensor over -- flip so the opposite side is facing the coil the spark line will also invert its polarity, a capacitive probe won't do that. Inductive probes work fine on my little DS201 Nano (same hardware as uScope) but my bigger scope won't play ball with an inductive probe on ignitions.

This was taken using the 3 turn inductive probe I made for the imobiliser thread using a little DSO201 Nano but I cannot get to produce a clear signal on my more powerful labscope no matter how I ring the changes on aquisition settings and filter. I may try iy on my Hantek 1008 if I get
time.
If my high school physics is correct this is actually showing the secondary current rather than voltage.

This is the sm#ame coil at idle taken with a Hantek capacitive probe -- it has been inverted as the spark is reverse polarity..

Here is a question, If you use an inductive probe, 1 side of the coil to ground on the scope, and the other side to a channel, if you want to use other channels than you would need to ground the scope to the chassis which might turn your inductive probe into a capacitive probe, right? I haven't tested this theory but if you ground one side of the coil, would the signal drop completely drop out. I'll do some of those tests soon,.

From my understanding, inductive probes work when there is an EM field passing through the center of the coil of wire versus on the sides. Similar to how an AMP Probe works. That seems to be where capacitive comes into play? Seems like there is a gray area when it comes to using a coil of wire for capacitive vs inductive. I think for our use, its more capacitive.

Here is a copy and paste from
www.quora.com/What-is-the-difference-bet...nd-inductive-sensors

Inductive sensors use a magnetic field to detect objects. Capacitive sensors use an electric field. In order to be sensed by an inductive sensor an object must be conductive. This limits suitable targets to metal objects (for the most part). In order to be sensed by a capacitive sensor the target doesn’t need to be conductive. A capacitive sensor will react to an object acting as a dielectric material as well as a conductive object. This makes metal and non-metal objects suitable targets.

So it seems an inductive pickup puts out its own Magnetic field?

Stickied.

Tyler wrote: Stickied.

Thanks Tyler

I order a magnet wire assortment kit which was delivered today so I am going to play around with that.

So far, no matter how many turns I have on a capacitive probe, the signal strength stays the same. Only reason I can see is some of the wraps go beyond the the edge of the coil. So Im going to make some with 22-30awg magnet wire and see what the results will be.

Really simple test is if you turn an inductive probe upside down the polarity of the signal inverts, also an inductive probe won't pick-up a signal from a plug wire only in close proximity to a coil.

A capacitive probe won't invert the signal if you flip it the other side up.

Interestingly because the coils magnetic field on a double coil shared between two companion cylinders an inductive probe l the trace will show the current flowing through both spark plugs.

Did some more testing. Made some more ignition probes from 22awg magnet wire.

Interestingly enough, The amount of turns didn't make a difference at all. All my probes produced the same signal strength with very minor differences. My original ones with 16 awg wire had 5 turns and my new ones are 22awg with 13 turns. Produced the same strength signal with the original one possibly having a bit more signal strength.

I also tried using the dual ended probe which I suppose is an inductive probe. Problem with that is using both ends, one end to the ground on the scope and one end to a channel 1, scope not grounded; the signal was very weak. Didn't seem to invert either when flipping the probe over. If disconnect the lead that is connected to the scope ground terminal, the signal drastically increases in strength. So it seems only probes with 1 wire works. The other end covered and not connected to anything.

Now I am wondering if surface area has anything to do with signal strength. I made a probe with 22awg magnet wire that had 3 turns, tiny mini probe and the signal was very weak. I am wondering how a penny or quarter soldered to a wire will do.

2 Probes, Both 13 turns. Wound differently. The flat probe worked the best


Also tried the entire roll of 22awg magnet wire, produced a weaker signal than the probe, probably has something to do with the orientation of the roll. Similar to the 13 turn tiny probe in the first picture above.


22awg,13 Turn Probe


22AWG 13 Turn Probe Signal


16awg 6 turn Dual ended probe which had a much weaker signal when using both ends.



Dual End Probe using Both Ends


Dual End Probe using One End. For some reason this probe is weaker on these coils but sometimes produces stronger signals on other vehicles. Odd. On my car, this probe was weak for what ever reason.

Andy.MacFadyen wrote: I dismantled an old style Hantek conventional plug wire clip on secondary probe that the cable had got burned on an exhaust, it not only had attenuation but used diode pairs on the output to protect the scope. I have the Auto-Ditex pick-up and also Hantek wand but I found I can often getl a useful trace using my just hand as capacitive probe

I find a lot of snags using ignition probes on plug top coils not the least because different brands of coil can produce totally different waveforms even on the same engine, and different probes can produce very different looking results.

Did you have pictures of the internals? I also have one of this, maybe I"ll take it apart. Its sometimes hard for me to wrap my head around the use of diods. I understand what they do for the most part.

I need to understand the fundamentals better to come up with a protection circuit for the probes in the event the signal is to strong or some how an arch gets into the probe which I think is going to be rare.

I'm confused by the term, capacitive sensor and inductive sensor. Capacitance is measured in farads. When you touch the screen on your smart phone the capacitance changes and this can be measured. Induction is when you produce emf in a conductor by a changing magnetic field. You are no doubt inducing a voltage into your probe. I believe the problem is your coil of wire is more of an antenna than two coupled coils on a transformer. Permeability and shape will have more of a factor on what kind of signal you detect. I could be wrong but this is my understanding. Ps. Great testing! I think i will try it myself before buying an official probe

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What about the idea of using a penny attached to alligator clip? Don't remember where I saw it.

I find that the home made probes pick up signals where the commercial ones don't.
The only thing is that the commercial ones have grounding, attenuation and other protection built in this is the only potential caveat to consider or mitigate.

Has anyone tried an abs sensor as a pick up for a probe ?

graywave wrote:

Andy.MacFadyen wrote: I dismantled an old style Hantek conventional plug wire clip on secondary probe that the cable had got burned on an exhaust, it not only had attenuation but used diode pairs on the output to protect the scope.

Did you have pictures of the internals? I also have one of this, maybe I"ll take it apart. Its sometimes hard for me to wrap my head around the use of diods. I understand what they do for the most part.

I need to understand the fundamentals better to come up with a protection circuit for the probes in the event the signal is to strong or some how an arch gets into the probe which I think is going to be rare.

Regular diodes are easy enough to understand. They're basically just electrical check valves which only allow current to flow in one direction.

I'm wondering if the diodes Andy found in that Hantek probe were actually TVS diodes there to dump leakage from the secondary to ground.

en.wikipedia.org/wiki/Transient-voltage-suppression_diode

Diode pairs are a common way to to provide over voltage protection in input stages of amplifiers in much the same way as zenner diode controls the charging voltage on a motor cycle

How about using resistance wire to make a cop probe, I wonder what the resistance of the coil should be? That will determine the amount of signal picked up I would imagine.

Hey Guys,

Thanx for all this good R&D!

I tried making my own COP probe recently before coming in here and this is what I found that helped me make one:








Haven't yet had time to make a multi-coil probe.
When I do, it'll be made from 1/8" copper flatbar strips.
The probe I made like the 1st link took me all of 15 minutes.
Dipping it and redipping it in PlastiCote is what you do when you have other things to do (just don't forget how many times you dipped it when you go back to redip!).

I made the copper cap pickup after it after testing the scope's ignition wire attenuated induction pickup lead by setting it on top of the coil, and then holding it beside the coil (COP system). Worked pretty good as bare metal. But not a good idea if you have spark leaks! I also tried the same using an alligator clip, but same warning applies.

I terminated the connector ends using male banana plugs b/c I cut the wires off an old DVM probe lead set and wanted to plug it into a cheap set of BNC/FBC leads. I think the thing cost about 2 bux US (not including the PlastiDip).

It's still a WIP, so will try using the magnet off a computer monitor cable to see if that helps absorb stray signals.

Otherwise, I haven't found a way to shunt a high voltage charge (like a jumping spark) off into lala land and not hurt my scope.

Cheers...

That’s some good stuff! You got my mind going now! Thanks for the info

Okay im pretty new to using scopes and i have a Zeus using a pico paddle probe and the probe wont work if the ground is hooked up. is this okay or do i have a problem?

Someone mentioned it earlier, and I have seen it too, where someone just put a penny on top of the coil and touched a regular probe to it.