Author Topic: DSO138, Not Even Once  (Read 1140 times)

Offline Mads Barnkob

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DSO138, Not Even Once
« on: January 20, 2020, 11:13:23 AM »
Before you buy a DSO138 or DSO150 from ebay, amazon, wish or aliexpress, it is important to understand what you are getting. The specifications are very loosely written and what looks good on paper is useless in practical use. Here I test the DSO138 specified at 200 kHz, but in reality it is worthless above 20 kHz.

Buying the right oscilloscope is knowing your work area limits and where it might be in the future. I recommend that you read: 12 things to consider when choosing an oscilloscope: https://www.mouser.com/pdfdocs/Tektronix12_things_to_consider1.pdf

For the Nyquist applet to play with: http://195.134.76.37/applets/AppletNyquist/Appl_Nyquist2.html

« Last Edit: January 20, 2020, 08:17:30 PM by Mads Barnkob »
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Offline Twospoons

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Re: DSO138, Not Even Once
« Reply #1 on: January 20, 2020, 08:31:54 PM »
At that price , what else would you expect?
And quite frankly I'd consider anything under 20MHz bw to be useless.

Offline klugesmith

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Re: DSO138, Not Even Once
« Reply #2 on: January 20, 2020, 11:10:05 PM »
Depends on what you're trying to capture.
20 MHz could be plenty fast for watching a detector:

In fact, selectable bandwidth reduction (by digital filtering) is a valuable feature in fast DSO's.
Easy way to reduce noise when the noise is unimportant.
« Last Edit: January 21, 2020, 08:19:44 PM by klugesmith »

Offline Mads Barnkob

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Re: DSO138, Not Even Once
« Reply #3 on: January 21, 2020, 08:37:14 AM »
At that price , what else would you expect?
And quite frankly I'd consider anything under 20MHz bw to be useless.

It is not so much what I expect, but what many first builders of a Tesla coil expects. I have gotten too many emails and messages about distorted wave forms measured with these toy scopes, that was my inspiration to make this video :)
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Offline Mysteriousduck

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Re: DSO138, Not Even Once
« Reply #4 on: January 21, 2020, 03:49:24 PM »
Ah, yes I've seen these. They seem like more of a toy, but I'm sure they are great for kids/beginners that want to get practice putting components together and probing simple circuits.

Any thoughts on this lil pup? Good way to spend $100 for a beginning hobbyist, or would the money be better spent on a used bench scope?

Signstek Nano ARM DS212
https://www.amazon.com/gp/product/B00HEZKY28/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

Offline Mads Barnkob

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Re: DSO138, Not Even Once
« Reply #5 on: January 21, 2020, 08:05:20 PM »
Ah, yes I've seen these. They seem like more of a toy, but I'm sure they are great for kids/beginners that want to get practice putting components together and probing simple circuits.

Any thoughts on this lil pup? Good way to spend $100 for a beginning hobbyist, or would the money be better spent on a used bench scope?

Signstek Nano ARM DS212
https://www.amazon.com/gp/product/B00HEZKY28/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

It is better than the DSO138, but it certainly is not worth 107$ from the specifications, maybe the size of it is worth it, if you can live with the limitations.

Signstek DS212 (107$):

0.0093 MHz/$
0.093 MSas/$
? data points/$

Rigol DS1052e (230$):
0.217 MHz/$
4.347 MSas/$
4347 data points/$

If you are looking to spend 100$ on a DSO, its better to spend 200$+ and get a real DSO.

Old used analog 20 MHz scopes should not be more than 10-20$ at a HAM market
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Offline Twospoons

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Re: DSO138, Not Even Once
« Reply #6 on: January 21, 2020, 10:54:44 PM »
Old used analog 20 MHz scopes should not be more than 10-20$ at a HAM market

Thats the thing isn't it. If you're on a limited budget the second hand market is where you will get the best value. A lot of that old gear is actually pretty damn good.  And for use around a TC an old analog scope is probably going to be more stable.
When I needed a spectrum analyser for a project I spent $2k on Ebay and got an '80s era TEK492. Original list price was $60k in 1985 dollars! It was a gorgeous piece of RF engineering and still worked great.

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Re: DSO138, Not Even Once
« Reply #6 on: January 21, 2020, 10:54:44 PM »

 


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