Author Topic: Scope noise - did I damage it?  (Read 1242 times)

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Offline Red Squirrel

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Scope noise - did I damage it?
« on: June 06, 2016, 04:18:32 am »
A while back I accidentally connected ground to the wrong (+5v at many amps) side of a circuit.  The probe went boom, it's dead.  But now I'm starting to wonder if I damaged my scope in that process.  I was using it (with another probe) to measure and noticed quite a lot of noise and did some troubleshooting and then it turns out even with no probes connected I get noise, that, and the 1st channel is not even centered.  I hit the factory reset button to ensure everything is factory.


 
The scope is a Siglent SDS 1072CML 70Mhz.  Is this normal noise to expect on a lower cost scope, or is there something wrong here?
 

Offline Dave

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Re: Scope noise - did I damage it?
« Reply #1 on: June 06, 2016, 04:58:09 am »
It doesn't look damaged to me.
Your vertical scale is set pretty low (2mV/div), so the input signal gets amplified quite a bit before it gets passed to the sampling circuit. You're looking at about 0.5mVpp here, which is a perfectly normal number for an average scope. The slight offset you see on CH1 is also normal and could probably be removed if went into the menu and performed an auto-cal.
<fellbuendel> it's arduino, you're not supposed to know anything about what you're doing
<fellbuendel> if you knew, you wouldn't be using it
 

Online tautech

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Re: Scope noise - did I damage it?
« Reply #2 on: June 06, 2016, 05:25:19 am »
You appear to have created a ground loop with your previous error, most of us have made that error however just as member Dave has said perform a Self Cal and report back.

But another thing I want you check with the DSO unplugged and powered down is continuity between all BNC's and mains earth.
The substantial currents involved can fuse the Gnd connections inside a scope if they're not robust enough so do that quick check. I've never seen a SDS1000 series Gnd connections damaged in this way but I know Tek had to do a factory recall of their TDS510 and 520 early models for fused Gnd connections.
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Offline Red Squirrel

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Re: Scope noise - did I damage it?
« Reply #3 on: June 06, 2016, 05:55:03 am »
Thanks did not even think of trying that, that fixed it!

Much less noise too... so some noise is normal then right?
 

Offline Dave

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Re: Scope noise - did I damage it?
« Reply #4 on: June 06, 2016, 06:38:16 am »
Much less noise too... so some noise is normal then right?
Yup.
<fellbuendel> it's arduino, you're not supposed to know anything about what you're doing
<fellbuendel> if you knew, you wouldn't be using it
 


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