Tooltop  ET120M  $50 DSO - Page 1
Forum section: electronics / testgear

author: rhb
author_rank: Super Contributor
timestamp: November 02, 2023, 11:02:42 pm
content: FWIW Out of curiosity I bought one of these:https://www.aliexpress.us/item/3256805182059777.htmlReal BW is 28 MHz both for the square wave source and the scope input measured by rise time for the square wave and adjusting the frequency of a Keysight 33622A until it dropped to the -3 dB point for the scope.Have Fun!Reg

author: rsjsouza
author_rank: Super Contributor
timestamp: November 02, 2023, 11:46:23 pm
content: Quite interesting for the price.

author: Aldo22
author_rank: Super Contributor
timestamp: November 03, 2023, 12:20:33 am
content: I think it's the same asMDS120M

author: rhb
author_rank: Super Contributor
timestamp: November 03, 2023, 04:54:44 pm
content: Looks like it's the same as the MDS120M. For value I think the Owon HDS2xxS series are much better.. I have an HDDS272S and it's really a 70 MHz DSO. Which foir portable use is plenty of BW.I also have a Hantek 2D42, but it's not as good.The 120M is a bit of a puzzle. Single channel 30 MHz with 1,10,100 & 1000 kHz square waves with a 30 MHz analog output section. For $50 delivered. In 1978 I paid $75 for a 5 MHz recurrent sweep Heathkit IO-18. This is so much better it's no contest.But consider the following T&M suite:TT/MDS 120M DSO $50nanoVNA $60tinySA $60BSIDE ESR02 $30Diode noise source $35DMM $30That's less than $300 USD for a rather complete RF T&M suite sufficient to do most HF design tasks. Not HPAK, but I've got those to compare to and have been quite impressed. That's a sea change from 30 years ago when $300 wouldn't buy a decent scope.The 120M looks to be approximately a single channel Finirsi at less than 1/2 the price. At a day's minimum wage take home pay it's pretty attractive for a student/new HS graduate.I'm busy building a 6 bay lab rack and populating it. Once that is done I'll post more detailed measurements.Have Fun!Reg

author: Aldo22
author_rank: Super Contributor
timestamp: November 03, 2023, 05:34:38 pm
content: Yes, the et120m is really cheap!But for not much more money, thesingle-channel Zeeweiioffers much more in every respect. Be it the 10mV vertical sensitivity or the signal generator with different waveforms, freely selectable frequency and duty cycle, video output, exportable screenshots etc.

author: rhb
author_rank: Super Contributor
timestamp: November 09, 2023, 11:23:32 pm
content: I just took some time for systematic testing using using my Keysight 33622A 120 MHz AWG.The Tooltop ET120M is complete utter crap. Displayed measurement values are spectacularly wrong, changing the timebase setting will make the signal disappear. In rolling mode on the builtin arb waveforms in the 33622A the waveform will drop in amplitude as it nears the left edge of the display. It will autoset on 120 MHz sine wave, but tell you the frequency is below 1 kHz.It is so badly aliased that you can't believe anything on the screen. Sometime when I'm really bored I'll take it apart and find out what the true sample rate is.Have Fun!Reg

author: rsjsouza
author_rank: Super Contributor
timestamp: November 10, 2023, 03:53:20 am
content: Reg, thanks for the insights. The ZT-702S (scope + DMM combo from Zotek) has a lot of aliasing past 5MHz (its specs are up to 10MHz), but at least it gives accurate measurements and waveforms up until that frequency. In comparison, it seems a more finished product: no screen blanking and no edge rolloff.In practice I have seen myself carrying the ZT-702S more often than a plain meter when I have to do equipment diagnostics in the field - at least I can get a waveform from the various power rails and detect if capacitors are starting to go down, not to mention an easy way to trace audio or otherwise slow signals. Debugging any serial communications protocol is entirely out of the question, but there are other instruments for that.