Re: Simple question about scope (DS1102E) and AC ripple

240mV sounds OK for unregulated DC just out of the bridge with a decent size filter cap. After a regulator, you should see muck less ripple than that.

Note that you can also measure AC ripple with just a (decent) DMM inn AC mode. It'll show RMS voltage, not peak-to-peak.

Altan Pinball <pinball@aaarfamily.com> wrote:

>Thanks! That was helpful. This is the first real thing I've tried with
>this scope.
>
>I'm getting about 250 mV as the AC ripple, which I assume ok.
>
>Using ac mode is quite helpful...
>
>On Aug 26, 2013, at 6:02 PM, Rodger Boots <rlboots2@gmail.com> wrote:
>
>Set horizontal to 5mS, trigger to Line mode, and vertical to 10 V and input
>coupling to DC. That will get you a good stable starting point. With probe
>not connected adjust vertical position to the center of screen. That gives
>you 0V in the center.
>
>To see just the ripple, switch input mode to AC and vertical sensitivity to
>1V. That gives you a good starting point.
>
>The way you did it before the scope put 0V towards the bottom and 25
>towards the top (and 12.5V in the center). When you increased the gain 0V
>went off the bottom and 25V off the top.
>On Aug 26, 2013 4:44 PM, "Altan (GAPAS)" <pinball@aaarfamily.com> wrote:
>
>>
>> Feel kind of stupid asking this, but you knows know this stuff well…
>>
>> I'm trying to use my DS1102E to look at the output of a bridge rectifier.
>> Goal is to see the voltage and whether any AC ripple exists.
>>
>> So I connect everything up, make sure the probe ground is connected to a
>> proper ground, and press the auto button.
>>
>> I see the voltage is going between about 25V and 26V. This is obviously
>> DC.
>>
>> If there was AC ripple, I assume I would see some large swings down to
>> zero and back up, yes? Or do I have that work.
>>
>> I'm also running into another problem. I wanted to "zoom in" on the area
>> between 25V and 26V, just to see what's going on there. The "auto" mode
>> picked 5V as the vertical size, so 0V is toward the bottom of the display
>> and 25V is toward the top. However, if I use the vertical scale knob and
>> change it from 5V to 2V (the next step down), I hear a little click and see
>> nothing. Even if I use the position knob to ensure I should see
>> something, it's not there. I'm certainly doing something wrong here.
>>
>> Bottom line: I'd appreciate any thoughts about measuring/viewing AC ripple
>> with a scope as well as any thoughts about why I cannot change the vertical
>> scale to < 5V in order to look more closely at the bouncing between 25V and
>> 26V.
>>
>> Thanks so much!
>>
>> … Altan
>> www.aaarpinball.com
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Received on Mon Aug 26 21:36:17 2013