Oscilloscope - no idea how to use it !

[Canadian1968]

So I picked up a cheap little oscilloscope to play around with.

I was hoping to get some reading from my ignitio coil , to try and compare with 2 different setups. Also I belive they can be useful for checking alternators among other things.

Basically just another tool I thought would be neat have and learn to use.

That's where the problem comes in! I don't really know how to use this thing ! I watched a few you tube video but they seem a bit vague and I'm not quite grasping some of it.

Here is my first wave form I got off my coil hooked up to the negative side.

The time frames and voltage scales all determine what you see on the screen and accuracy of the readings ?

People that know how to use these will be able to tell if I have my settings correct from my pics.

Just looking for some input.

 

[Billccm]

Looks good to me. You have it triggered and capturing a waveform that's 728v p-p.

You can change the time base and zoom in on the ringing.

Somewhere I have a link to a white paper that explains how to use a oscilloscope as a ignition system analyzer. You use clothespins, foil tape, and 0.01uf capacitors to couple the coil output wire to channel 1 as the trigger and couple the cylinder under test to channel 2. You view the ringing to determine if the spark plug, wire, rotor, distributor cap are in good shape.

You are teaching yourself a great skill as a oscilloscope can measure voltages, give transient information, and help troubleshooting digital communication in automobiles, etc.

 

[Billccm]

This makes your scope useful


ignition_waveforms.pdf https://share.google/i21Vl9BDLdopCYaPJ

 

[Canadian1968]

What is the 728v p-p mean ?

My understanding is that I have it set on 100v scale so each square is 100v . My spike or fire of the plug is about 400+ volts would that be correct . I scaled the time in 2 different patterns 200 and 500us.

How much is a US.

Just liken vertical squares being 100v each , going horizontal the squares would equal 200 or 500 us per square ?

 

[Billccm]

You are correct. Each vertical division is 100V per your scale. The "Vp-p" is volts peak to peak. A us is microsecond which is 1*10e-6 seconds. I'm impressed you picked this up easily.

 

[Lefty71]

One more reason to miss our grandfathers.... they would know (or at least mine would)

 

[65CopCar]

Do you have a 10x probe?

 

[65CopCar]

So what you see is decent info. But what do you want to see? The discharge pulse peak voltage? If so, you should be using the trigger function. Start high and then bring it down slowly till it triggers. That way you don't miss the peaks.

 

[Canadian1968]

So what you see is decent info. But what do you want to see? The discharge pulse peak voltage? If so, you should be using the trigger function. Start high and then bring it down slowly till it triggers. That way you don't miss the peaks.

I belive that is the correct probe to be using ?

What I was really interested in was dwell and coil saturation. From what I read, I don't really see that in my wave signal. Should there not be a drop in voltage as the primary charges , and then if a slight rise if gets full saturated and limiter kicks in ? Then the big spike as the " switch " opens and the field collapse?

The current setup is a regular orange mopar box with ballast and canister coil FYI

 

[Canadian1968]

Also..... why do I have such a huge negative .

I get it now pkpk = peak to peak duh haha

So I'm up 400 volts then negative 300v ? How is that possible ? Should it not hit 0 volts and stop?

 

[65CopCar]

View attachment 1883940View attachment 1883941

I belive that is the correct probe to be using ?

What I was really interested in was dwell and coil saturation. From what I read, I don't really see that in my wave signal. Should there not be a drop in voltage as the primary charges , and then if a slight rise if gets full saturated and limiter kicks in ? Then the big spike as the " switch " opens and the field collapse?

The current setup is a regular orange mopar box with ballast and canister coil FYI

Yes - 10x probe so your scope is set properly. For this measurement, its a good choice.

I don't believe that you are reading negative. I think your trace is not set at the middle of the the screen which would be zero. What you have is fine. I believe all of your reading is positive.

However the screen shot confuses me. The trace moves from left to right so the high voltage pulse comes first then the much longer lower pulse, then the pulse goes away. So that would mean the HV pulse happens when the voltage hits the coil not when it shuts the voltage off. That does not really make sense to me. Maybe someone else knows.

Also change your time scale to a longer time period like 5 ms to see multiple firings just to play with it.

 

[oldbee]

One more reason to miss our grandfathers.... they would know (or at least mine would)

Exactly, my dad knew all that and I forgot what I knew after high school. Used to play around all the time in grade school with his.

 

[6872n73]

Another exercise is to check your wall outlet for 60hz and 120v,I was surprised.

 

[65CopCar]

Ok. makes sense now. Brain cramp. I forgot that the negative side gets grounded. So the spike is when the ground opens the the second pulse is the spark duration.

Didn't listen to the whole thing, but this is the best video on the subject I found. You are measuring the primary voltage.

 

[Canadian1968]

Yes I'm measuring primary I don't have a clamp to read the secondary side.

 

[65CopCar]

Yes I'm measuring primary I don't have a clamp to read the secondary side.

After watching another video, I am going to buy this secondary probe. I already have a planned use for it.

https://www.aeswave.com/15-inch-WyzeProbe-for-Secondary-Ignition-and-COP-p8764.html

 

[Dodge-Scatpack]

I use a PicoScope 4425. The software is free to download if you just want to play around with their guided tests for some basic training.

Their website has a lot of information on how to use a scope and what your base settings should be for certain applications.

PicoScope automotive lab scopes and diagnostic equipment

 

[65CopCar]

I use a PicoScope 4425. The software is free to download if you just want to play around with their guided tests for some basic training.

Their website has a lot of information on how to use a scope and what your base settings should be for certain applications.

PicoScope automotive lab scopes and diagnostic equipment

I have a love hate relationship with picoscope. My favorite is my old Tektronix THS730A. That was before Tektronix got bought and went under the same ownership as Fluke. Tektronix then gave the hand held scope market to Fluke and just focused on the high end scope market. I don't much care for the Fluke scopes but they do work.

 

[WileE]

Just watch out if this happens :

 

[65CopCar]

Actually you have a probe that can be set to 1X or 10X. You have it set for 10X which is what your scope is set for. Voltage numbers will be wrong if the scope is set for something other than the probe you are using.