Author Topic: How to "Zero" a scope's reading  (Read 833 times)

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Offline ksat44Topic starter

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How to "Zero" a scope's reading
« on: August 07, 2022, 06:16:53 am »
Hope this question isn't too basic, but I was wondering what setting is used to "zero" or rel out a reading you get on a scope. I'm picking up some low level noise prior to taking a measurement that I'd like the scope to ignore and just start at the 0V mark. I have a DC amp clamp, as well, which has no zeroing button on it that I was hoping I could do on the scope end of things in the same fashion, too.

I see a feature called filtering which appears to do what I'm talking about, but I'm not quite sure that is the appropriate setting to use in my situation.

Many thanks for any help...

« Last Edit: August 07, 2022, 07:13:45 am by ksat44 »
 

Offline JustMeHere

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Re: How to "Zero" a scope's reading
« Reply #1 on: August 07, 2022, 07:16:09 am »
 

Offline tautech

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Re: How to "Zero" a scope's reading
« Reply #2 on: August 07, 2022, 11:24:02 am »
ksat44
I'd be very concerned if I owned a scope that wouldn't detect spurious signals when instead you need know how to manage them and understand what they might be so to know when to ignore them.

The world is an electrically noisy place, much of it due to EMI/RFI from all manner of SMPS that surround us however some are much better than others.
I had a customer that was adamant we had sold him a faulty scope as he had a 22KHz signal present in all scope measurements however having seen this before the hard part was convincing him otherwise however after check surrounding rooms and turning OFF all appliances and wallwarts the culprit was found in a power socket behind a curtain in the same room as the scope !

With a scope, the probe if used incorrectly is a mighty fine antenna but one can take advantage of this fact using it like a near field probe which can prove very useful on occasions where it can be used to sense ignition pulses from small petrol motors as an aid to tuning.

Anyways back to your noise, are you using a DSO ?
Screenshots please showing noise frequency and the active channel input menu.
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Offline wn1fju

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Re: How to "Zero" a scope's reading
« Reply #3 on: August 07, 2022, 11:32:56 am »
Yes, your question seems a bit ambiguous.  If it is the case that you have a signal with a DC offset, so that the baseline of the scope isn't at zero, you could always set the scope for AC coupling - this will eliminate the offset.  If it is simply noise that sits around zero, then indeed reducing the scope's bandwidth (the filter setting) will reduce the noise somewhat. 

But as tautech says, you want a scope to see the actual truth - you wouldn't want one that doesn't.

 

Offline Andreas

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Re: How to "Zero" a scope's reading
« Reply #4 on: August 07, 2022, 06:10:11 pm »
Hello,

on my scope there are several options to remove the DC-Offset of a DC current clamp
which are created by the current clamp offset of the operational amplifier or partly also the earth magnet field.

the easiest way is to use the "offset" function with "auto-zero" in the channel menue.
(of course you can also enter a manual offset value).

Other options are use "zero all ranges" in the channel menu or use a math function in the math menue.

with best regards

Andreas

 


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