# Beginners Oscilloscope - what to chose?

#### SamR

Joined Mar 19, 2019
2,259
Just for grins and giggles. I connected my chinesium Cleegee Signal Generator (60MHz) to my Siglent SDS1102CMML+.

Using RG6U coax 75Ω (was sold as a "scope cable") @1X
1MHz

10MHz

20MHz crapped out

Using RG8X coax 50Ω @1X
1MHz

10MHz

20MHz

30MHz

100MHz Probe @1X Calibration

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#### SamR

Joined Mar 19, 2019
2,259
100MHz Probe @1X
1MHz

5MHz

10MHz crapped out

100MHz Probe @10X
1MHz

5MHz

10MHz

15MHz

30MHz crapped out

#### nsaspook

Joined Aug 27, 2009
7,356
Scope calibration signal:
Bottom trace 200MHz probe with tip ground connected to calibrator ground point.
Top trace 100MHz probe with no tip ground.

#### tautech

Joined Oct 8, 2019
118
100MHz Probe @1X

10MHz crapped out
As expected, rated to 6 Mhz.

100MHz Probe @10X

30MHz crapped out
View attachment 213675
This:
I connected my chinesium Cleegee Signal Generator (60MHz)
Fast square waves are hard. Everything must be terminated correctly.

Wanna start pushing frequencies then a sine wave is the easiest to work with.
Eg, the new 100 MHz DSO I mentioned earlier at its -3dB BW point. (0.707 V with a 1V input)

#### SamR

Joined Mar 19, 2019
2,259
As a first scope, I had no expectations to go much beyond audio frequencies or low RF. This suits me fine. I have another chinesium signal generator that is supposed to go to 20MHz and is not any better if not worse. It craps out ~10MHz. Both work fine at lower Frequencies and do sweep with all the standard waveforms so they serve their purpose for me. But when they advertise an upper freq for a signal generator you expect a signal and not just noise at that freq. Yup, square waves are kind of the acid test for finding upper freq limit and the scope will do much better on sine.

#### tautech

Joined Oct 8, 2019
118
Yup, square waves are kind of the acid test for finding upper freq limit and the scope will do much better on sine.
Yep and all instruments are generally BW rated by their sine wave performance.
Fast edge squares are the test of step response and some incorrectly use them to establish BW and while it is true risetime is related to BW it's not the exact measure of such.
When edges are used in DSO's the interpolation method and vector vs dots display used can produce results that are not consistent with the real sampled data points which lead to overshoots displayed that just aren't there.

A very good post on this matter addressing unfounded claims against several brands is here:
https://www.eevblog.com/forum/testgear/scope-wars/msg3121780/#msg3121780

#### bob2

Joined Jun 15, 2019
180
I'm looking closely at this oscilloscope at a good price in China $280. Two channels, 100MHz. UTD2102CEX Digital Storage Oscilloscope. #### tautech Joined Oct 8, 2019 118 I'm looking closely at this oscilloscope at a good price in China$ 280.
Two channels, 100MHz.
UTD2102CEX Digital Storage Oscilloscope.
Pitiful memory depth of just 25kpts.
My advice is is not to touch it with a 40' barge pole.
A sane requirement to get some use of the real power of a DSO is a couple of Mpts at least. More is better.

#### SamR

Joined Mar 19, 2019
2,259
That is ~what I paid for my SDS1102CML+ direct from the Siglent US distributor that has much better specs. The Uni T scope seems to be a scaled-down version of most other DSOs that one very generous review claimed "which is more suitable for general signal measurements". In other words, can't do as much.

#### tautech

Joined Oct 8, 2019
118
Yes Sam, memory depth is everything in a DSO.
Here in a DSO like the OP has purchased in Zoom mode we can use the dual timebase with the primary timebase set slow capturing a lot of info which in this case is a data stream and inspect it more closely in the zoomed timebase in which we can navigate by panning across all of it with the H Pos control.

#### bob2

Joined Jun 15, 2019
180
An example of a complex signal.

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