Hi folks, I have a cheap handheld oscilloscope (Dso2512G) I use for automotive diagnostics.
I just bought a Hantek HT25 probe for the scope so I can sample the secondary ignition system spark waveform on cars etc.
It picks up the signal pretty clearly although it is inverted, it appears upside down on the screen.
I see online most people use Pico software and can easily click on “invert signal” and problem solved, although my handheld doesn’t have this option.
I also saw another person using a pocket pro in between the probe and the scope they used, they were able to switch polarity using the banana plugs of the pocket pro and that put the signal the correct way round for them so it was no longer inverted.

So I’m wondering if there may be a solution for me to do the same or similar although my probe and scope use BNC connectors. I’m pretty open to messing with the probe in order to find a solution as the probe is cheap so I don’t mind trying some polarity reassigning or similar electrical witchcraft. I’m not in a hurry as I already have functioning tools for reading spark waveforms but wanted to add this probe to the kit.
Any ideas or recommendations are appreciated, if this is in the wrong section my bad.

thanks

 

It picks up the signal pretty clearly although it is inverted, it appears upside down on the screen.

What signal are you looking at that you know is inverted?
The spark voltage could very well be negative, as there's no standard for that polarity.

But, according to the scope manual (below), a short press of the CH1/CH2 function will change the channel polarity:

 

What signal are you looking at that you know is inverted?
The spark voltage could very well be negative, as there's no standard for that polarity.

But, according to the scope manual (below), a short press of the CH1/CH2 function will change the channel polarity:
View attachment 342198

Hi there, thanks for the reply. I see it says it changes the priority of the channels, not sure if that also changes polarity? Could give it a try.

The spark waveform usually appears as below…

but at the moment it’s inverted so goes down not up, so when I turn the scope upside down and look at it the waveform is the correct way up, but it is then backwards.

Its a funny one, but I’m sure some trickery can fix it lol.

Thanks

 

If this is a battery operated hand held oscilloscope, simply swap the probe’s signal and ground. You can only use one probe at a time, i.e. you cannot have multiple ground connections.

 

swap the probe’s signal and ground.

Connection is through BNC, not Banana

 

Admittedly - I DON'T KNOW - but if the dwell signal is correctly oriented then I'd guess that the ignition pulse IS negative. The dwell shows an increase in your example. If that's what you're seeing on YOUR scope then yes, I'd assume it's negative. If, however, the dwell shows it decreasing then the signal is inverted. And I don't know how to rectify that. Not without building a cable to swap the signals. i.e. ground to pin and pin to ground. But that could introduce all kinds of noise in your signal.

 

Connection is through BNC, not Banana

The probe is connected to the oscilloscope via a BNC connector.
Just interchange the probe end tip and grounding clip.

 

Thanks folks.
I was looking through the cables I already have and I see I have a bnc to banana male.
I saw this adaptor on ebay which should fit between the bnc to banana and the Hantek HT25 spark lead probe.
I’m going try just switching the polarity with this and hopefully I’ll get the same result as some others did.

Thanks

 

The probe is connected to the oscilloscope via a BNC connector.
Just interchange the the probe end tip and grounding clip.

I will try this idea too, it may well work also.

thanks

 

I see it says it changes the priority of the channels,

Ahh yes, I misread priority as polarity.
Not sure what "priority" means here.

 

The probe is connected to the oscilloscope via a BNC connector.
Just interchange the probe end tip and grounding clip.

Don't know why I didn't think of that. But considering that as a possibility, given the signal is a high energy spark pulse, connecting the probe tip to ground and the ground clip to the spark pulse, is there a chance that you could send a high energy pulse directly into the scope? Could that present a possible chance of damaging the scope? I know this is a hand held scope, so it may be unlikely to be an issue. But one would prefer to be sure.

 

Not sure what "priority" means here.

Could have to do with the trigger. My scope can be set to select a positive going pulse on channel 1 or 2 and trigger a reading. It can also select a negative going pulse on 1 or 2.