Bad scope?

[upand_at_them]

I'm still learning to use my new Rigol oscilloscope and noticed the following. Does this look normal? The scope ground unconnected, probe touching my finger.

Probe/scope set to 10X:


Probe/scope set to 1X:


I'm guessing the ~60Hz is coming from the mains. But 2.5V P-P? And the scope counter shows a different frequency than the Measure function? And shouldn't the 1X and 10X show the same values since the scope is handling the division?

 

[BrownOut]

I'm guessing the ~60Hz is coming from the mains. But 2.5V P-P?

That's normal.

And the scope counter shows a different frequency than the Measure function?

You probably need to set some cursors.

And shouldn't the 1X and 10X show the same values since the scope is handling the division?

They won't be the same. You probably have a 1:1 probe setting and a 10:1 probe setting. The 1:1 setting will show actual voltage, and the 10:1 setting will show 1/10th voltage.

 

[squishy36]

Try connecting the probe to the calibration signal. Your manual will tell you what the amplitude and frequency of the calibration signal is (it's usually around a volt and 1 kHz). Then you can a) make sure your settings are correct to read the correct voltage and waveform parameters and b) make sure your probe is properly compensated. Google probe compensation if you don't know what that is...

 

[upand_at_them]

They won't be the same. You probably have a 1:1 probe setting and a 10:1 probe setting. The 1:1 setting will show actual voltage, and the 10:1 setting will show 1/10th voltage.

But the 1X and 10X are settings on the scope as well as the probe. And I'm setting both. I'm expecting that the scope setting compensates for the probe setting so that I see the true value.

Try connecting the probe to the calibration signal.

Yes, I have already verified the calibration signal. It tested fine many times. My concern is that I had constructed an oscillator circuit and when I had probed the output I got the same signals as in the images above, whether the circuit was powered or not. I was expecting either a square wave or no signal. When I accidentally touched the probe to my finger I got the same result and was confused. How will I be able to discern a flag signal if that's what I get?

 

[BrownOut]

I'd say something is wrong with your oscillator. Or else you're not connecting your probe ground correctly.

 

[saturation]

This appears as normal behavior. The scope inputs are very sensitive, and you will easily pick up EMI. If you make a loop by clipping the ground clip to the input tip you'll make an antenna and stabilize the readings you see from ambient.

The Rigol does not automatically set probe scale, you must manually assign it or the readouts will be 1/10. The hardware and software counters do not necessarily match: the hardware counter counts input pulses while the software counter measures waveform peaks on the screen [ likewise other measurements are based and scaled to the screen, not actual measurements by a specific device like a voltmeter], ... pretty much what you see is unreliable until you ground the probe properly.

What appears as more noise in the what I think is the x10 setting is because the default probes, assuming you have RP2200 are rated to ~ 200 MHz in x10, and only 6 MHz in X1, so the filtering effect of the X1 is removed.

A lot of good info is in the manual [well written compared to many Chinese label DSOs] and it will pay to work through its examples on usage.

Enjoy.