BNC oscilloscope reverse polarity adapter ?
BNC oscilloscope reverse polarity adapter ?
(OP)
I have searched for a few hours to no avail, for an adapter to connect to my oscilloscope probe, to reverse its polarity.
I have found some which look reasonably close to what I want,(but not quite, at extortionate prices). I only use a scope for simple pretty basic functions. I bought a Picoscope and was dissapointed to find that the INVERT function doesn't work very nicely. It inverts the waveform, but also displays the original. Then when you hide the original, the trigger diamond gets hidden also, but it's in the wrong place anyway, since it is on the opposite side of the zero line.
It's a pain in the butt.
The simple solution is a polarity adapter to fit on the end of the probe, but I can't find one anywhere. The closest I can find is an rfa 8333, but even though the connection ends are correct, the pin genders aren't correct. One side is and the other isn't.
One side needs to resemble the scope connection and the other the probe connector, but any I can find aren't like that.
Surely such a thing exists?
Am I looking for a jack -> jack, or a plug -> plug ?
Thanks
Here's an example of what I don't want, since both have a male pin internally.
I know I can make an adapter from bits and pieces but I prefer to buy the bespoke par if I can.
https://www.fairviewmicrowave.com/images/productPD...
I have found some which look reasonably close to what I want,(but not quite, at extortionate prices). I only use a scope for simple pretty basic functions. I bought a Picoscope and was dissapointed to find that the INVERT function doesn't work very nicely. It inverts the waveform, but also displays the original. Then when you hide the original, the trigger diamond gets hidden also, but it's in the wrong place anyway, since it is on the opposite side of the zero line.
It's a pain in the butt.
The simple solution is a polarity adapter to fit on the end of the probe, but I can't find one anywhere. The closest I can find is an rfa 8333, but even though the connection ends are correct, the pin genders aren't correct. One side is and the other isn't.
One side needs to resemble the scope connection and the other the probe connector, but any I can find aren't like that.
Surely such a thing exists?
Am I looking for a jack -> jack, or a plug -> plug ?
Thanks
Here's an example of what I don't want, since both have a male pin internally.
I know I can make an adapter from bits and pieces but I prefer to buy the bespoke par if I can.
https://www.fairviewmicrowave.com/images/productPD...





RE: BNC oscilloscope reverse polarity adapter ?
You should be able to move the trigger diamond by clicking and dragging it.
RE: BNC oscilloscope reverse polarity adapter ?
Otherwise, the math tool (A-B) is quite useful if you do not need extreme speed or accuracy.
It turns two grounded channels into one floating channel and by grounding the A and measure with B, I usually get the job done. If you want to apply a "global" minus [-(A-B)] to the result, it can be done.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: BNC oscilloscope reverse polarity adapter ?
@mudandsnow, the diamond becomes invisible when you hide the original channel, so its a real pita to fine tune things when you have to keep turning the hidden channel back on, just to get at the diamond. And when the hidden channel is unhidden, the two traces superimposed on one another just becomes a big mess, and you can hardly even tell where it is you want to place your diamond.
RE: BNC oscilloscope reverse polarity adapter ?
https://youtu.be/E1jFKz_DSP0
RE: BNC oscilloscope reverse polarity adapter ?
eg:
Threads on the outside of a device = male for electrical conduit.
Threads on the outside of a device = male for threaded water pipe.
Threads on the outside of a device = male for hydraulic fittings.
Threads on the outside of a device = male for bolts.
Threads on the outside of a device = female for connectors.
But I saw it on the internet so I must be wrong.
If you reverse the polarity with the leads, you may be sending the signal to the frame of the scope.
Also the outer part of the connector will be at signal potential.
Possibly OK for signal work but don't do it on a power circuit.
Just ground your probe and use the ground clip to pick up the signal.
If that won't work, then a special connector may not work.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: BNC oscilloscope reverse polarity adapter ?
Not really an issue in this automotive application.
"Just ground your probe and use the ground clip to pick up the signal."
I wish it was that simple.
Unfortunately it has both ends terminated with crimped connectors.
It is a capacitive pickup so changing its orientation doesn't change the signal polarity unlike an inductive type.
Its a bit like this one.
https://i.ebayimg.com/images/a/%28KGrHqUOKj8E3I1nQ...
RE: BNC oscilloscope reverse polarity adapter ?
A simple test:
wrap a couple of inches of tin foil around the cable to be measured.
Clip your ground clamp to the tin foil.
Clamp your inductive pickup to ground.
Check to see if that inverts the signal.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: BNC oscilloscope reverse polarity adapter ?
"If you can't reverse the signal by reversing the connections"
Sorry I didn't say that, I said orientation.
By orientation I mean how you invert the inductive pick up on a strobe light in order to reverse the polarity of the signal.
(Strobe light clamps have a marker saying "THIS SIDE TO SPARK PLUG", but even that is only a suggestion. If you use it on a twin output coil, one spark plug spark jumps TO the ground electrode, and the mating spark from the same coil jumps FROM the ground electrode, so in such a case you really just have to try it and flip it accordingly).
This capacitive type pickup works different so flipping the clamp has no effect on the signal.
On the other hand, uncrimping the end and swapping how its terminated most definitely will invert the signal.
How can it do otherwise.
RE: BNC oscilloscope reverse polarity adapter ?
If not, you have something like this:
And then, a simple cable switch doesn't help.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: BNC oscilloscope reverse polarity adapter ?
RE: BNC oscilloscope reverse polarity adapter ?
But if you have an "ordinary" scope (yes, I know that you are using Pico, but not what model) then most models have a much larger capacitance from the "cold" (or GND) connector to Earth than from the "hot" (center) connector to Earth. And in most cases, there is a direct connection to Earth.
So, if you swap leads, you will load the signal (capacitively coupled spark signal) in a way that makes both quantitative and qualitative measurements impossible. And, if the cold connector is grounded, you will not get much signal at all.
The screen you show seems to be taken with a symmetrical front end. If so, your problem wasn't a problem from the beginning. What Model do you use? And what SW? The screen shown doesn't look like an ordinary Pico screen.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: BNC oscilloscope reverse polarity adapter ?
RE: BNC oscilloscope reverse polarity adapter ?
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: BNC oscilloscope reverse polarity adapter ?
I just will use this for comparative tests in automotive applications.
On a Snapon scope, you press, INVERT and the jobs done.
Again, the Snapon is obviously not for doing definitive accurate voltage tests but rather comparisons.
I'm surprised Pico didn't include such a simple option by default.
I have since found that there is a way to define custom probe in their software which has a multiply factor.
It is simply a case of making this factor -ve 1 and the jobs done.
Thanks for everyone's input.
I'm now sorted
RE: BNC oscilloscope reverse polarity adapter ?