Oscilloscope reading

[noyan]

Hi,
I have bought an oscilloscope for testing my own built kwak clock out. But, i am newbie with the oscilloscope I wonder if the signal out of the Kwak clock is good or not? Can you please review the photographs for me?
Thanks a lot,
Noyan

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An externally hosted image should be here but it was not working when we last tested it.

 

[lcsaszar]

Did you measure it with a probe?

 

[noyan]

Yes

 

[jan.didden]

What is the bandwidth spec for the scope?
The frequency looks good.

Edit: Looks to me like a 25MHz scope. See the fundamental and a few harmonics.

jan

 

[noyan]

Oscilloscope is;
UNI-T UTD2102CEL 100MHZ Digital Storage Oscilloscope 7" LCD 1G Sa/s Sampling Rate
Thanks
Noyan

 

[biju55]

There are lot of videos in the you tube regarding the usage of an oscilloscope . that would help you .

 

[lcsaszar]

There seems to be some excessive capacitive load. It might be caused by the probe itself (if the test point is a high impedance out), or inherent to the circuit, or caused by the next stage, or caused by cable capacitance, etc. It is hard to tell without knowing at which point do you measure, and what is the capacitance of your probe.

 

[AKN]

Probe in X1 or X10 mode?

 

[jan.didden]

It might help if you could post a schematic of the oscillator you build.

jan

 

[emuman100]

This always made me wonder-how much bandwidth is required to see the pulse train of the clock? This looks like the fundamental and a few harmonics, like an above poster said. For an 11.2896MHz clock, how much bandwidth?

 

[Salas]

Probe in X1 or X10 mode?

Exactly. If at X1 the probe won't have more than 10MHZ bandwidth. Use X10 if X1 was the case.

 

[Salas]

This always made me wonder-how much bandwidth is required to see the pulse train of the clock? This looks like the fundamental and a few harmonics, like an above poster said. For an 11.2896MHz clock, how much bandwidth?

10X. I.e. circa 110MHZ to see the pulse well. Now if there are weird and fast ringings you want to observe in fine fidelity on that pulse, then 20X is even crisper.

 

[gman76]

Did you adjust the probe compensator for the proper tuning? That scope prolly has a sq wave output on the front. Adjust tuning cap for no overshoot/undershoot.

 

[noyan]

According to your advise, i used 10x probes for measuring. Firstly, i have calibrated probes with 1kHz square wave. Then i measured the clock waves in same time at the point no:1 and point no:2 (See the Kwak clock schematic). Channel 1 of the oscilloscope is showing the wave at red point no 2. Channel 2 is showing the wave at red point no 1. Before and after the comparator chip, waves are different looking.
Any comment about the Kwak clock out signal? (CH1)
Thank you
Noyan

Shematic of Kwak clock:

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Calibrated 10x probes:

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Waves measured with channel 1 (at the top) and channel 2 (at the bottom)

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[Salas]

I am not aware of that application specs, but C3 should be playing a filtering role I suppose.

 

[cliffforrest]

I am not aware of that application specs, but C3 should be playing a filtering role I suppose.

Er, no! C3 is just decoupling the DC comparator threshold level.

OK, filtering in a sense ... but should not change the waveshape.

 

[Salas]

Ah, OK. Now he can probe ~11MHZ squares as in blue trace, so some expert Kwak clock advice is the next step. I am outta here.

 

[gman76]

Is the inverting input of the comparator within the common mode range of the input stage? If you change the pot setting to a DC level that is slightly above gnd does that change the output? I dont know this exact comparator but the o/p ought to switching between 5V and gnd. Maybe you should probe the o/p directly, at pin 8. It seems odd that the o/p is a small 500mV signal.

 

[emuman100]

10X. I.e. circa 110MHZ to see the pulse well. Now if there are weird and fast ringings you want to observe in fine fidelity on that pulse, then 20X is even crisper.

Would you recommend 10 to 20 times as a general rule?

 

[noyan]

When i am turning the RV1 trimpot, it is changing the shape of the clock signal. I will try to add a video to show it.