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Topic: Horrible noise when attaching leads. (Read 6215 times) previous topic - next topic

Horrible noise when attaching leads.

When just combined the OLS to the computer, and click to capture (at all speeds and parameters) to see what I watch:

that is normal.
BUT! when he joined probe cable or any other wire, just one, then looms the following picture:

What to do?
Update from the archive ols_0308.

Re: Horrible noise when attaching leads.

Reply #1 –
Is connected to the first channel of the earth. As you can see everything is fine. And on the other channels NOISE incomprehensible at any speed capture, and other outputs which I did not connect, they just weigh in the air, running in idle.

Re: Horrible noise when attaching leads.

Reply #2 –
I believe it is noise from, for example, lights in your workspace. The cable acts as an antenna. Ground any unused channels in the channel group that is active, that should make it go away. You might also try upgrading the firmware to the latest version.
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Re: Horrible noise when attaching leads.

Reply #3 –
This works well for me.  A couple of 100k SIP resistor packs to terminate the inputs.

Re: Horrible noise when attaching leads.

Reply #4 –
My soldering skills have never been very good so I don't like the idea of soldering sip resisters to the board.  I will probably cut a small length of stripboard and add jumpers and sip resisters. 

If the board is ever re-designed, one change might be to add an additional contact locations for ground.

Re: Horrible noise when attaching leads.

Reply #5 –
[quote author="Randy"]This works well for me.  A couple of 100k SIP resistor packs to terminate the inputs.[/quote]

What are you doing here? your connecting all pins from both channels together with a resistor string?

Re: Horrible noise when attaching leads.

Reply #6 –
[quote author="felix52"]My soldering skills have never been very good so I don't like the idea of soldering sip resisters to the board.  I will probably cut a small length of stripboard and add jumpers and sip resisters. 

If the board is ever re-designed, one change might be to add an additional contact locations for ground.[/quote]

I wouldnt reccomend that resistor method. Do what I did; its the simplest by far.

Both the first and last pin are ground. So what I do is I plug the first ground pin to the circuit under test; then say I use just two channels; so I plug those into the circuit; then I plug in a strip of female headers into the rest of the pins. That strip of female headers are all soldered together. I simply ran a screw driver over the leads so they bent down to the next one, and so on... Then simply soldered each together...

So using that method; I have the first ground running to the last ground; which in turn runs ground to all the un-used pins. It cant get much simpler.

EDIT: reading what I just wrote; it sounds confusing but its really not; im just not great at explaining it. So I had a professional engineering company describe the method and how it works; to a professional graphics design company. who in turn had to hire a professional PR company to work together to design the perfect images to describe the method I explained above... It was very expensive; but worth it.

Here's how its created and used
[attachment=1]

Heres how it works
[attachment=0]

Re: Horrible noise when attaching leads.

Reply #8 –
Its the same basic idea; just alot more effort and time taken to perform the same task. plus its got to be annoying to poke all those jumpers in; i just plug one solid block on it and im good to go.. its pretty though.

Re: Horrible noise when attaching leads.

Reply #9 –
[quote author="BrentBXR"][quote author="Randy"]This works well for me.  A couple of 100k SIP resistor packs to terminate the inputs.[/quote]

What are you doing here? your connecting all pins from both channels together with a resistor string?[/quote]

Those SIP packs have each resistor tied to a common pin.  The 8-pin has seven resistors and the 10-pin has nine.  They are arranged so that the common pins are connected to the grounds at each end of the connector, one is flipped over in the opposite direction than the other.  The end result is a 100k resistor from each input pin to ground.  I would have used a higher value but I had these on hand.

Randy

Re: Horrible noise when attaching leads.

Reply #10 –
Having those resistors in there might screw up with the bus you're analyzing, since you basically have a pulldown on all the lines, which will be inserted in the circuit once you connect the probes.

Re: Horrible noise when attaching leads.

Reply #11 –
100k Ohms should have little effect.  I would recommend something higher though, maybe 470k or so.  I had the 100k SIPS in my junk box.  Keeps the pins from floating.

Randy

Re: Horrible noise when attaching leads.

Reply #12 –
[quote author="MickM"]Do you have fluorescent lights?[/quote]
OH!!!  That is a really good suggestion!

I remember when I was getting my degree how I struggled and struggled against an electrical noise problem in a circuit I designed.  I was so engrossed in my troubleshooting that I completely failed to think that the noise was coming from the fluorescent lights.  I turned off the lights, and the noise problem disappeared.

Paraphrasing an old axiom, the pitfalls are always in the details.  And wow... electronics is really loaded with details.
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Max