New toy(?) scope, DSO154pro, 1ch, claimed 40MS/s

[tunk]

New small scope, this time hopefully with real specs:
- Sampling rate 40MS/s
- Bandwidth 1MHz/18MHz
- Sensistivity 20mV/Div ~ 10V/Div
- Time Base 50ns ~ 10s
- Generator Frequency: 0-500K, 3.0V
- Screen 2.4 inch / Resolution 320*240
- Size 87*58*18mm

http://www.sigpeak.com/productinfo/dso154pro.html
http://www.sigpeak.com/download/ZEEWEII-dso154pro_UserGuide_En.pdf
https://youtu.be/BmaMLNnN-rc

[tautech]

New small scope, this time hopefully with real specs:
- Sampling rate 40MS/s
- Bandwidth 1MHz/18MHz
- Sensistivity 20mV/Div ~ 10V/Div
- Time Base 50ns ~ 10s
- Generator Frequency: 0-500K, 3.0V
- Screen 2.4 inch / Resolution 320*240
- Size 87*58*18mm

http://www.sigpeak.com/productinfo/dso154pro.html
http://www.sigpeak.com/download/ZEEWEII-dso154pro_UserGuide_En.pdf
https://youtu.be/BmaMLNnN-rc

Useless in the real world for checking ripple on a supply rail. Some instruments specify 5mV max ripple, how can you see that with such poor sensitivity.

[ataradov]

I don't know why we need so many of those cheap scopes. They are useless.

The only thing I can see something like this being useful if you are making one your self from scratch as a somewhat advanced hardware/firmware project.

[james_s]

I think something like this is probably adequate for kids tinkering with electronics. I'm spoiled now but I would have been thrilled to have something like that when I was a kid. Limited, yes, but not useless. Sort of a VW Beetle or Lada, they weren't great cars by any measure but they were affordable and better than walking.

[BillyO]

I agree.  They have their place but probably more akin to a Wal-Mart bicycle. 

Using the older DSO-138 and a $15 FG I was able show my nephew how to plot the FR of simple RC audio frequency low-pass, high-pass, band-pass and band-stop filters.  A $100K Keysight would probably give more precise results but I doubt he would learn anything more.

[tunk]

Looks like there's two models:
- 18MHz, battery, P6100 probe, US $37
- 1MHz, no battery, US $28
https://www.aliexpress.com/item/1005004972406356.html

[Grandchuck]

What a great gift: this scope,  an inexpensive DMM, and an Arudino kit with parts and project ideas!  Could send the recipient down the EE path!

[tatel]

@tunk: I ordered it just after see this post. It arrived a week ago, but I have been quite busy

[tatel]

Some more pics

[tatel]

I have to say, I'm quite happy with that purchase. Since I bought my benchtop scope, etc, more than a year ago, I have done almost nothing with it. Mostly for a lack of spare time, but also:

a) Complication factor: Benchtop oscilloscope has many controls and a thick manual. This toy is absolutely basic in comparation, so one has to work with the essential settings. It has allowed me begin to understand the most basics aspects of operation faster than the benchtop device.

b) Fear factor: Not afraid to screw this thing, it's dirty cheap.

c) Comparation factor: When I saw that outputting a 5Vpp square vawe this toyscope was giving reads higher than 6 Vpp, I asked myself why. When the benchtop scope did the same, I knew it was me screwing up it all. Then a search in the forum of course gave me the answer.

BTW, I think you all will find quite interesting some advice that appears in tis oscilloscope manual. Looks a little bit kamikaze to me. Please see attachment.

All in all, happy with it. Sad I don't have spare time right now, I was getting quite fun. Will have to wait perhaps two or three months...

[gcwills]

To add to this thread I recently purchased a DSO154pro mainly to see how the lower spec no battery version would perform.
I hoped there would be a simple hack to increase the 1Mhz bandwidth spec to the 18Mhz claimed for the battery version.
Turns out that the lower spec no battery version appears to be identical to the 18Mhz version. My unit had no difficulty displaying a 15Mhz sine input.
It appears then that the lower 1Mhz spec for the battery version may be a strategy to encourage the purchase of the more expensive version??
Another thing I was keen to investigate was the possibility of adding an 18650 Li-Ion battery to my unit. Again, it appears that the "no battery" version is identical to the more expensive DSO as my unit has a 2 pin socket for a battery and an 18650 cell scavenged from an old notebook battery was able to be connected to the socket and charged via the USB C power input.
As Dave would say - "winner winner chicken dinner"
As others have commented the DSO154pro is a pretty basic unit however it significantly exceeds the performance of the 200Khz DSO138 for much the same amount of money.
With an 18Mhz bandwidth, a max 50ns timebase, variable persistence, roll mode, and inbuilt 0.01Hz to 500Khz function generator it has been a lot of fun to play with. 

[Fungus]

Useless in the real world for checking ripple on a supply rail. Some instruments specify 5mV max ripple, how can you see that with such poor sensitivity.

It's also only single channel and has no bode plot or serial decoders... 

It appears then that the lower 1Mhz spec for the battery version may be a strategy to encourage the purchase of the more expensive version?? 

The 1MHz limit might come from the crocodile clip that comes with the cheap one vs. the real probe that comes with the expensive one.

[tautech]

Useless in the real world for checking ripple on a supply rail. Some instruments specify 5mV max ripple, how can you see that with such poor sensitivity.

It's also only single channel and has no bode plot or serial decoders... 

Nowhere as important as having adequate sensitivity for normal tasks.
Anyways, if it were able to a single channel is all that's required for decoding UART.
Did so today as a demo to a customer.

[gcwills]

An update on the DSO154pro - after putting the function generator through its paces my unit topped out with a max frequency of 1Mhz. Twice the claimed 500Khz spec.

[Fungus]

An update on the DSO154pro - after putting the function generator through its paces my unit topped out with a max frequency of 1Mhz. Twice the claimed 500Khz spec.

I just ordered mine... I got the one with the battery and real probe. 

The 'scope will be very useful at Arduino club and the siggen is icing on the cake.

Seems like a bargain for 32 Euros (shipping included!)

[Matamipru]

Strange 1mhz or 18mhz. Strange 40msa or 16kbps 50ns ... Sure the chipset accepts sensitivity of 10mv or lower

[Fungus]

I got mine this morning.   

Much smaller than I expected - literally the size of a credit card! (but 2cm thick...)

Battery came charged so I just turned it on and it worked.

Menus are very easy to navigate, it all seems to work as expected. Didn't need to read the manual.

For 30-odd Euros I've got no complaints at all!   

[tatel]

Hi, I tried the rise time bandwidth calculation method mentioned by Fungus in another thread.

On the attached picture, PSU output was 1.34V checked with DMM. I did try other values but the results were always about the same. So if I'm getting it right, bandwidth would be about 9MHz? Half the spec?

Well, it has been a happy hour anyway.

I would love to use my Rigol DG811, after the upgrade, it should be good until some 60 MHz. However I think I'm missing something. Using coax+50 ohm terminator, atenuation should be set to 1x, but then the bandwidth would be lesser?

Edit: typos

 

[Fungus]

Here's a 5V, 16MHz square wave on mine:


I just connected it up and pressed "Auto". It locked onto the signal no problem.

As expected you can only see a sine wave, but it's there.... 

[tatel]

So you simply put atenuation at 10x with coax+terminator?

Edit: ni de coña... this has to be the probe. I see your screen shows Zeeweii, mine doesn't. Different software versions perhaps? My square wave becomes sinusoidal sooner

[Fungus]

Here's the awesome setup I was using above:


It's an Arduino clone that can run at 32MHz and the supplied probe at 10x. I told it to toggle an I/O pin as fast as possible and that makes a 16MHz square wave.

Reading between the lines: If it's sampling at 40Mhz and producing that display then it must be doing sin(x)/x interpolation. Maybe that's what the FPGA is for...

[Fungus]

Edit: ni de coña...

El tuyo no?

I see your screen shows Zeeweii, mine doesn't. Different software versions perhaps? My square wave becomes sinusoidal sooner

It doesn't show a software version.

If the bandwidth is correct then the square wave will start to become sinusoidal as you go above 5Mhz (ie. when the first harmonic is at 20Mhz).

FWIW: If I output a 4Mhz square wave it shows the 4MHz base wave and the 16MHz harmonic:


Textbook stuff. 

[Fungus]

I think I found a hidden feature: If you long-press the "Auto" button it switches into a mode where it sets the horizontal timebase continuously to match the input signal.

I tried pressing all the buttons at power-on, nothing seems to happen - no cheat codes here.

PS: It can also stop and then zoom out. Take that, Siglent!

If only it had two channels and a RS232/I2C decoder, it would be 100% awesome for "Arduino" work. You can't have everything at this price though.   

[Fungus]

...

The CPU is a "WinnerMicro W806"

The chip labelled "3PEAK 3PA9280" is the A/D converter but the datasheet says it's only rated to 32MHz.

GS8094 = Quad opamp

They seem to have lasered off a chip number. Is that the FPGA? (I guess it must be, by elimination...)

[hallo1]

Something interesting is that there is an USB to UART converter chip on board.
After powering on the scope and connect it to some PC you can see a serial port showing up.
But if you open the port the scope just immediately shut itself down! Some self-protect method?

This is very likely to be a programming port, but the programming tool of W806 only have one function (program flash) so there is no easy way to dump the firmware currently.

[tatel]

Textbook stuff. 

Yeah, I obviously have much to read, and even more to play

[tautech]

PS: It can also stop and then zoom out. Take that, Siglent!

Oh so you have 500uV sensitivity, 14Mpts memory and a Zoom mode that provides for zoom out, do you?

You may not know yet but processing all memory available impacts on WFPS rates allowing scopes to miss events.

[Fungus]

You may not know yet but processing all memory available impacts on WFPS rates allowing scopes to miss events.

Um, it only has to zoom out in STOP mode, not when it's processing events.

[Matamipru]

My scope is 34.1mhz in square wave . One bug detected?

[Matamipru]

Unfortunate my probe came faulty. I can't reset my oscilloscope

[ataradov]

Even real scopes have trouble measuring the frequency if there is not a full period or a few periods  are displayed.

What is wrong with the probes and what that has to do with the scope reset?

[Matamipru]

It's a long story, it's a lot of emails with the factory. The tip screw does not work.

https://youtu.be/eEznWkH_MVg

My scope is 34mhz ? Thanks

[Matamipru]

I'm sorry, I sent the wrong video

https://youtu.be/D-gZIZkC1Fs

[Matamipru]

I want to reset because over time the memory accumulates unnecessary data. The manual reset method does not work, nor the method that the factory indicated in the email

[ataradov]

I don't understand what the issue is. As they replied, probe compensation is only implemented in 10X mode. So, the adjustment capacitor will not do anything. This is not a defect, this is how probes work.

Just use 10X mode and forget that 1X exists, it is not useful in most day to day tasks.

No, it is not 34 MHz, it is an error in measurement based on the incomplete data. You need to adjust the time scale so that a few periods are visible. There is no way to measure a "frequency" of a simple edge transition.

[Fungus]

Unfortunate my probe came faulty.

That's not faulty, that's normal.



1x probes never have full bandwidth, you should use 10x for normal use.

[Fungus]

My scope is 34mhz ? Thanks

No.
a) A 40Mhz sampler can never show a 34MHz signal correctly.
b) It can only measure frequency correctly when there's several pulses on screen.

I'm sorry, I sent the wrong video

https://youtu.be/D-gZIZkC1Fs

It all looks correct to me. Now you need to find out why... 

[__Jack__]

Hello.
I got my device yesterday but it seems I have strange situation. Theoretically I bought "full" version ( 18MHz, 1x10 probe, internal battery ). Unfortunatelly, it seems to have no more than about... 2.5MHz of 3dB bandwith. I tested it via sine wave from external signal generator using crocodiles cable. I know that this cable  is worse than regular probe but it is only few MHz. When I looped internal generator ( 1Mhz squere wave ) via this cable, signal looked very limited and distorted. Absolutely it was not similar to what other colegues inserted in their pictures.
Is it possible I got 1MHz version or something is damaged?

Regards
Jack

[Fungus]

I tested it via sine wave from external signal generator using crocodiles cable. I know that this cable  is worse than regular probe but it is only few MHz.

Is it possible I got 1MHz version or something is damaged?

It's the cable. You'll see the same with the probe in 1x mode.

The only time you get full bandwidth is with the probe in 10x mode.

[Matamipru]

The alligator show square wave better than probe x1 and x10. I want to reset my dso154pro. Can you reset yours? Greetings

[Fungus]

The alligator show square wave better than probe x1 and x10.

It should be about the same as 1x.

Here's mine with the probe on 1x:


And here with the probe on 10x:


There's quite a difference in bandwidth.

(voltage is low because I'm testing battery life and there's only one pixel of battery left...)

[Fungus]

(voltage is low because I'm testing battery life and there's only one pixel of battery left...)

Update: Battery indicator turned red and some strange glitches started to appear on the signal:

[Fungus]

Update2: Battery indicator is flashing and the glitches are getting much worse:

[__Jack__]

Thanks colleagues. You were right. In my measurements I have  both crocodiles and probe x1 connected together.
Yesterday I made comparisons with my Rigol osciloscope and it turned out that x1 probe has some kind of lowpass filter.
Even Zeeweii manufacturer told me about it when I described them my problems.
I do not know why they attache such probe,  but any other probes I have , do not cut bandwith by lowpass filter on x1 position.

Regards
Jack

[Fungus]

I do not know why they attache such probe,  but any other probes I have , do not cut bandwith by lowpass filter on x1 position.

Try your Rigol probe on this 'scope... 

[__Jack__]

My Rigol has two probes. I tried one of them yesterday.
I had no bandwith limitations neither on x1 nor on x10 positions.
I wiil try to do some tests again on everything I find at home

Regards
Jack

[tatel]

[tatel]

Got this from the vendor:

Hi, dso154pro there was an update, it mainly added zeeweii icons, there is not much difference in function. Due to hardware limitations, it does not support firmware updates.

[Matamipru]

14mhz SINE wave at -3db , stable square wave at 500khz

Please someone tell me which oscilloscope can show lossless 3mhz square wave?  thanks

[ataradov]

Ideal square wave has infinite spectrum, so no scope can show that. But generally bandwidth 10x the frequency of the square wave shows acceptable results, something that can be called square.

For square waves it is generally better to talk about rise time rather than bandwidth. Those parameters are directly related, but the rise time is easier to visualize and reason about.

Rise time = 0.35 / F_3db. So pick a rise time that you think still looks like a square to you, and you will know the minimum necessary bandwidth  to get that.

And your generator would also have some limited rise time, and you will not be able to observe it better than that. So another way to know what is the best scope for the task is to understand your source.

[Fungus]

Please someone tell me which oscilloscope can show lossless 3mhz square wave?  thanks

No oscilloscope is "lossless" but a 50Mhz oscilloscope will show a 3MHz square wave very well.

[techcornertv]

Hi everyone,

My humble contribution for this thread, I just released yesterday a video about it.


https://youtu.be/ugzLNDy6DEs



Cheers!
Hugo

[Matamipru]

there will be no worldwide interest in this product.it is open dangerous for alternating voltage. it only works for that.  so dso150 is safer and satisfies. they should have concentrated all efforts on the main parts. No in battery, probes and other things the customer of this type of product likes to do. if the software was open it would have already sold a zillion units.they think they keep and have the amazing secret.  profit policy on resale of parts is ignored.  will get rich selling the software 

[hallo1]

Got this from the vendor:

Hi, dso154pro there was an update, it mainly added zeeweii icons, there is not much difference in function. Due to hardware limitations, it does not support firmware updates.

The scope is VERY likely to support firmware update considering there is an "unused" USB to serial converter chip on board.

[Fungus]

The scope is VERY likely to support firmware update considering there is an "unused" USB to serial converter chip on board.

But it may be very difficult to hack if we don't have example firmware to work with or any clues about the hardware.

[Dave_g8]

For general information, I received a DSO154PPro recently and noticed that the PCB was marked “V1.4”.



This has a few notable differences compared to the previous versions. The changes may be due to component obsolescence, functional updates and/or cost reduction.

- The generation of the negative power supply rail has been modified.
This now uses a similar arrangement to other Zeeweii models, with a switched mode step-up regulator followed by a step-down regulator. This may be to ensure correct behaviour at low battery levels. The large electrolytic decoupling capacitors associated with the previous switching regulator have been removed and since the updated regulators have a higher switching frequency, smaller ceramic capacitors have been used.

- The device used for the data acquisition and waveform generation has been changed.
The device is marked “AG32VF303KCU6”, which appears to be an MCU with a RISC-V core with RV32IMAFC support and should be suitable for signal processing applications.

- The ADC has been changed.
The device is marked “MS9280”, which is a 10-bit ADC. The least significant 2-bits are not connected. There is a minor change in the analogue circuit around the 74HC4051 multiplexer which may be related to the ADC update.

- The waveform generator output circuit has been modified slightly.
The resistor ladder network has been changed to discrete resistors and there are some modifications around the “8091” output amplifier.

I also own a Rigol oscilloscope which is more capable for higher frequency, complex triggering and serial decoding, but the DSO154Pro is still a handy pocket oscilloscope with built in waveform generation and has a quick and simple user interface.

There are freely available 3D printable case models, which I used to provide some degree of protection to the unit.



Overall, for the cost, the DSO154Pro provides excellent functionality and performance compared to other devices in the price bracket.

[mojoe]

I'm supposed to get mine on Wednesday. I have four better scopes, but I ordered this to take with me in my carry-on luggage. For use with microcontroller hobby stuff while away from home, this should be sufficient. I could take my HDS272S, but it's much larger, and I pack very light.

[mojoe]

My itty bitty scope arrived a day early. I'll do some testing later, after it's charged.

Mine is version 1.3. I don't know if that is good or bad. As we all know, later versions could either be due to improvements or bug fixes, or due to cost cutting where they removed components to save half a cent.

Test results to follow.

Edit: as usual, the charging is not real USB-C.

[mojoe]

Test results.

Up to 8 MHz, a 1 Vpp sine wave looks good and measures at 1 Vpp. Beyond that, the voltage starts dropping slowly. I didn't bother looking for the 3 dB point, as from 10 MHz to 18 MHz, everything starts dancing, and the measured voltage isn't stable. At 18 MHz, it's still somewhere around 890 mV, but fluctuating wildly. Beyond 19 MHz, it just won't sync.

As for square waves, at 1 Mhz, the waveform starts to look like Bart Simpson, but is still quite usable. At 5 MHz, you've lost all but the 3rd harmonic, but can still tell it's a square wave.

So, it looks like the bandwidth is actually about 18 MHz, and any harmonics beyond are lost.

Yes, a toy scope, but still quite useful for up to 5-10 MHz, depending on the waveform. For my travel use, it will do nicely. If I drop it or run over it, I won't feel too bad, considering the cost. This would make a nice, inexpensive gift for a budding hobbyist.

Those of us who have been around electronics for quite a while will remember when we wished we could have afforded a boat anchor scope that only did 5 MHz (and you could heat the house with it). So don't sneer too much at this little scope.

[Dave_g8]

Hi,
The traces look similar to what I have seen on the V1.4 hardware (see attached), so I expect they are functionally the same.




The ripple on the square wave trace is due to the sin(x)/x interpolation that is used.
A simple example of reconstructing a sampled wave is shown attached.
- Equivalent to 40Msa/s and a 5MHz square wave.
- The red trace is the reconstructed signal



It would be useful to be able to turn off the interpolation in some cases to see the actual sampled waveform, but provided the limitations of the oscilloscope are understood, all is as expected.

[videobruce]

This "thing" wouldn't even qualify for a "toy" !!

[Fungus]

This "thing" wouldn't even qualify for a "toy" !!

Nonsense, they're awesome for what they are. Nobody's forcing you to read this thread.

This is exactly what you'd expect from a device that can only "see" the first two harmonics of a square wave:


ie. It can see the 5Mhz and 15Mhz sine waves in the signal but not the 25MHz sine wave (or higher)

[Dave_g8]

Hi,
I agree that the DSO154Pro is excellent for the price, but you do need to be aware of its limitations.

The pre-shoot and overshoot on the square wave from the external signal generator is an effect of the sin(x)/x interpolation which is used by the oscilloscope to construct the displayed waveform.
The rise/fall time of the external signal is approximately 10ns.
The images below shows the Rigol (sampling 1Gsa/s) and DSO154Pro (sampling 40Msa/s) displayed waveforms for the 1MHz signal from the external signal generator.



There is no evidence of an anti-aliasing filter on the front end of the DSO154Pro which would limit the bandwidth to the ADC, so the results are as expected.
 
With the in-built signal generator at 1MHz, there is less ringing because the rise/fall time is limited by the waveform generator circuit and therefore the displayed waveform is closer to representing the actual signal.



If the time-base on the DSO154Pro is set to 200us/Div or greater, the sin(x)/x interpolation appears to be turned off. The trace below shows the displayed waveform with the external 1MHz square wave signal. In this case the trace is joining the dots between samples.

[mojoe]

I had the rise time set to the fastest, which is 8.9 ns, if I remember. Thus, the Bart Simpson look.

I'll have to try changing the timebase to get "connect the dots". BTW, "200us/Div or greater" would imply to me more time per divison, not less. It's a matter of perspective. Once I looked at your screen grab, I knew what you meant.

Just a bit ago, I used my "toy" scope for something useful, without having to either take everything to the bench, or find room for a larger scope at the computer (not enough room). I bought some DS3231SN RTC modules, and wanted to test them to make sure they were actually the SN version, and not the M version. The M version only outputs 1 Hz, and cannot do 1024, 4096 and 8292 Hz, like the SN will. Also, the M has slightly worse long term accuracy.

I had previously ordered what were listed as SN, but received M. They were returned.

This type of use is exactly why I bought this tiny scope. I can take it in my carry-on luggage, along with some microcontroller stuff, to have something to do while I'm away for long periods for work.

[Fungus]

I agree that the DSO154Pro is excellent for the price, but you do need to be aware of its limitations.

That's also true of $20,0000 oscilloscopes.

[tatel]

Hi,
I agree that the DSO154Pro is excellent for the price, but you do need to be aware of its limitations.

Of course, however I see more bang for the buck in it than in most other "toyscopes". AFAIK, none of these two-channel low cost models appearing in the last times is able to do a differential measurement. Even if some offer "FFT". If you can't do differential measurements on a low BW 2-channels o'scope, is there much of an advantage in having two channels? At double DSO154Pro's price? Should they have differential measurement, I would think otherwise.

So, as next step in the ladder after DSO154Pro, I would rather get an old Hameg 20 MHz than, say, Zeeweii's DSO2512G. About the same bandwidth, but traces are much more stable after you get over half the device's bandwidth, and they do differential measurements. At first it seemed impossible to get one of these under 100€ in Europe, but now I have a couple of them (I still need to decide which one will remain here). One can get 50 MHz bandwidth for a little bit more (another couple Hameg 604-605 was found). Needed to go on the hunt for about six months however.

Personally I rather prefer these old boat anchors than one of the new, low-bandwith 2-channel o'scopes appearing now. Unless you really need the portability, of course. But when speaking about portability, DSO154Pro is enough for me. With a separated DMM. YMMV.

Don't really know about those Zoyis, etc, but for what they seem to be, I'd stick to my DSO154Pro, I think. Perhaps the Owons, I don't know. They seem to be quite good and portable. I miss differential measurement on them, tho, and have seen complaints about they getting hot, then becoming somewhat unstable. Others will know better I guess. But they look to me as probably the better of the low cost 2 channel oscilloscope-DMM combos, so I do see some value on them. Just not my choice.

Newbies on a really tight budget, looking for a cheap o'scope to begin learning, will find more value on DSO154Pro than in most other low-cost offerings. It will remain useful as a portable thing after they outgrow it, just for peanuts. On the next price step, old CRO's will also remain useful after outgrowing them. To, say, look at PSUs without risking to blow up any brand new 4-channel benchscope. For little more. Just my thoughts.

[BillyO]

In this video @ 15:40 the bandwidth of the 154Pro is tested and does just fine @ 18MHz.  No where near -3dB.

[Dave_g8]

In this video @ 15:40 the bandwidth of the 154Pro is tested and does just fine @ 18MHz.  No where near -3dB.

Hi,
Yes, the analogue bandwidth of the front end is greater than 18MHz.
Because the sampling rate of the ADC is only 40MSa/s, this means that the resultant displayed waveform after sin(x)/x interpolation for a square wave input signal will have ripple before and after the transitions which is not present on the actual signal.
So although you will see reasonable results for high frequency sine wave inputs, for square waves the result is not so good.
If you have sine waves greater than twice the sampling frequency the results will be invalid due to aliasing. For example, a 21MHz sine wave input will be displayed as 19MHz, 22MHz as 18MHz etc..
This behaviour will be the same for all sampling oscilloscopes, but when sampling at say 2GSa/s, the analogue front-end bandwidth will be apparent and interpolation effects will be much less noticeable.

[BillyO]

Hi,
Yes, the analogue bandwidth of the front end is greater than 18MHz.
Because the sampling rate of the ADC is only 40MSa/s, this means that the resultant displayed waveform after sin(x)/x interpolation for a square wave input signal will have ripple before and after the transitions which is not present on the actual signal.
So although you will see reasonable results for high frequency sine wave inputs, for square waves the result is not so good.
If you have sine waves greater than twice the sampling frequency the results will be invalid due to aliasing. For example, a 21MHz sine wave input will be displayed as 19MHz, 22MHz as 18MHz etc..
This behaviour will be the same for all sampling oscilloscopes, but when sampling at say 2GSa/s, the analogue front-end bandwidth will be apparent and interpolation effects will be much less noticeable.

Right, this will be the same for ANY scope, even an analog scope.  Put a 100MHz square wave into a 100MHz analog scope and the result will be far more sinusoidal than square as the front end acts like a low-pass filter removing most of the harmonics above 100MHz.  However, I see everyone rating this scope at 15MHz or even less.  That's just wrong.  It has an honest 18MHz bandwidth.  Bandwidth is always specified for a sine wave.  To display a decent square wave you need to de-rate the BW by a factor of about 10.  So a 18MHz scope will do a fair job of showing a sub 1.8MHz square wave.  This is true of any scope at any price.  Even then you will have considerable "ripple" on both the top and bottom of the waveform due to the harmonics that make it through the effective filtering of the front end.  This is expected behavior.  Of course you can expect a $3000 scope to deal with that better than a $30 scope but to even make the comparison is ridiculous.  So, I stand by my assertion that his is an 18MHz scope and I'll also add that it's insanely good for the $30 it costs.

It completely blows away the 5MHz scope I got in 1978 (which I had to build myself) that cost me the equivalent of $1000 in today's money.  On top of that it is arguably the best $30 scope you can currently get.

That's the way I see it anyway.

[Dave_g8]

Hi Bill,
As I stated in earlier posts, the DSO154Pro provides excellent functionality and performance compared to other devices in the price bracket.
However, I do not agree that an analogue oscilloscope would show the same ripple or wrong frequency, since this is purely an effect of the sampling and interpolation used.

[BillyO]

An analog scope would just show very close to a sine wave, you might have to educe the frequency from the period.

With my 154, using an 18MHz square wave at 5Vrms from a Siglent SDG1062X and properly terminated I get an apparently amplitude modulated sinusoidal waveform.  The amplitude modulation is being caused by aliasing.  I don't get that with a pure sine wave, plus it's not getting the amplitude right either (I have the probe setting at 10X so divide by 10).  But you can see it's showing the correct frequency.  At anything much higher than 18MHz (like 19MHz) it can no longer properly detect the frequency not matter what the waveform.

[Aldo22]

It completely blows away the 5MHz scope I got in 1978 (which I had to build myself) that cost me the equivalent of $1000 in today's money.  On top of that it is arguably the best $30 scope you can currently get.

That's probably true.
Nevertheless, I would pay a few extra bucks and buy a DSO1511G.
In my opinion it is even better value for money.

https://www.aliexpress.com/item/1005001969702720.html

[Dave_g8]

Hi Bill,
If you inject a 22MHz sine wave you will see a stable 18MHz sine wave on the DSO154Pro (as attached).

[BillyO]

There is no evidence of an anti-aliasing filter on the front end of the DSO154Pro which would limit the bandwidth to the ADC, so the results are as expected.
 
With the in-built signal generator at 1MHz, there is less ringing because the rise/fall time is limited by the waveform generator circuit and therefore the displayed waveform is closer to representing the actual signal.

If the time-base on the DSO154Pro is set to 200us/Div or greater, the sin(x)/x interpolation appears to be turned off. The trace below shows the displayed waveform with the external 1MHz square wave signal. In this case the trace is joining the dots between samples.

Yes, and the first case is more accurate.

Below the first image is like yours with the sin(x)/x.  The 2nd image is taken with a 600MHz scope using a 750MHz 1.5pF probe, so it is showing the signal being produced by the Zeeweii pretty accurately.  It matches what the Zeeweii itself shows pretty exactly.

[BillyO]

Hi Bill,
If you inject a 22MHz sine wave you will see a stable 18MHz sine wave on the DSO154Pro (as attached).
(Attachment Link)

Okay, I am not sure what the point is.  Are you saying it's not working right if you use it beyond it's specifications?  Why would you expect it to?

My Siglent SDS2504 will show a 800MHz signal pretty well, but it's a $3000 scope, not $30.

Zeeweii say the 154Pro is an 18MHz scope and it meets this specification.  What more do you need? 

[Fungus]

In this video @ 15:40 the bandwidth of the 154Pro is tested and does just fine @ 18MHz.  No where near -3dB.

Yes, the analogue bandwidth of the front end is greater than 18MHz.

Yep. I've got one, if I put in a 22Mhz sine wave I see a perfect 18MHz sine wave on screen (as predicted).

You need to go up to maybe 28Mhz before you see much attenuation.

Those things are nice little gadgets but aliasing is a big problem even at "Arduino" frequencies.

[Dave_g8]

Hi Bill,
If you inject a 1MHz square wave with a faster edge, you will see more of a difference.
The top trace is a Rigol sampling at 1GSa/s and there is no ripple.

The DSO154Pro is fine, but you may not be seeing a true representation of the signal.

[BillyO]

Hi Bill,
If you inject a 1MHz square wave with a faster edge, you will see more of a difference.
The top trace is a Rigol sampling at 1GSa/s and there is no ripple.

The DSO154Pro is fine, but you may not be seeing a true representation of the signal.

(Attachment Link)

You are seeing exactly what you should be seeing for a scope with 18MHz bandwidth.  Harmonics above 18MHz will begin to be attenuated.  Your image is showing good contributions from the first 16 or so harmonics.  That is 100% expected for an 18MHz scope.  I am willing to bet the other image comes from a scope with far greater bandwidth.  In this case it has nothing to do with sample rate.  Just bandwidth.

[Dave_g8]

Hi Bill.
If you put a 1MHz square wave into a 20MHz analogue oscilloscope, you will not see the ripple as seen on the DSO154Pro.

[BillyO]

Hi Bill.
If you put a 1MHz square wave into a 20MHz analogue oscilloscope, you will not see the ripple as seen on the DSO154Pro.

Well, you will but it will be harder to see because of the response of an analog scope.

Here is an image of a square wave composed of the first 16 harmonics.  Does it look familliar?

[BillyO]

If you want to play around with it the tool is here: https://www.ultracad.com/square.htm

[Dave_g8]

Hi Bill.
See below a simulation of a 1MHz square wave with a 100ps rise/fall time passed through a 20MHz low pass filter.

[BillyO]

Hi Bill.
See below a simulation of a 1MHz square wave with a 100ps rise/fall time passed through a 20MHz low pass filter.

(Attachment Link)

Correct, and that would be the response of an analog scope.  I have no problem with that.

Oh, okay.  I get what you are saying.  Yes, the 40MHz sample rate will have an effect as harmonics beyond the 16th or so will not even be detected.

Sorry for the misunderstanding.  My mind was in a different place.

[Dave_g8]

Hi Bill,
No problem.
It is the sin(x)/x reconstruction without any anti-aliasing filter feeding the ADC that screws things up when injecting a square wave with fast edges.
That's why the square wave from the DSO154Pro test generator look reasonable, because it is effectively band limited.
Regards, Dave

[BillyO]

Hi Bill,
No problem.
It is the sin(x)/x reconstruction without any anti-aliasing filter feeding the ADC that screws things up when injecting a square wave with fast edges.
That's why the square wave from the DSO154Pro test generator look reasonable, because it is effectively band limited.
Regards, Dave

Yes, agreed.

[Fungus]

The DSO154Pro is fine, but you may not be seeing a true representation of the signal.

Square waves are the sum of a lot of sine waves.

You're seeing the sum of the sine waves that an 18MHz 'scope can see.

At higher frequencies the same thing will happen on your Rigol.

[Dave_g8]

Hi,
The analogue bandwidth of the DSO154 will be much greater than 18MHz.

Attached is a capture on the DSO154Pro with a 1Hz (2V Pk-Pk) square wave input from a signal generator (fast edge speed).



You can see the same ringing before and after the transition which is a result of the display reconstruction.

I don’t want to repeat all the discussions on sin(x)/x, Gibbs, but in my opinion the displayed waveform is not always representative of the input signal.

If I sample a 1Hz square wave at 40MSa/s (25ns) and then join the dots, I will not see the pre and post edge ringing.
For completeness, the Excel graph below shows an example of sampling a square wave.
The dotted yellow line is joining the dots between samples and the red line is the sin(x)/x reconstruction. The frequency of the ringing is half of the sampling frequency.

[sizziff]

I don’t want to repeat all the discussions on sin(x)/x, Gibbs, but in my opinion the displayed waveform is not always representative of the input signal.

I also hold the opinion that the wave at the top of the pulse is the result of the Sinx/x interpolation
On the Hantek 2d72 oscilloscope (250Ms), it displays a square wave of more than 10 MHz very similar.
The straight line of linear interpolation is replaced by sinx/x arcs, which makes it possible to plausibly restore the sinusoidal signal, but gives such artifacts on the square wave signal.

[Dave_g8]

Hi,
The attached link provides a summary of the pros and cons for different interpolation methods.
https://saving.em.keysight.com/en/used/knowledge/glossary/oscilloscopes/what-are-interpolation-methods

The sin(x)/x is great for band limited signals, but not so good for signals with fast transitions.

[Dave_g8]

Hi,
For general information I noticed an undocumented feature in the DSO154Pro.
Since the feature is not covered in the documentation, it may be firmware/hardware dependant and not fully tested.
Whilst in the “Disp” Menu, press the “Stop” button.


Two options are available “F_Meter” and “Counter” as shown below.
Note: The options are mutually exclusive.


Enable the “F_Meter” by moving to the “ON” icon and pressing the “OK” button.


The “F_Meter” works irrespective of the time-base setting as shown below, unlike the normal frequency reading used in “Meas” options which is based on the waveform shown on the screen.


Notes
- The “F_Meter” seems to use its own auto trigger level setting, irrespective of the setting in the trigger menu.
- The “F_Meter” reading is updated whilst in run mode and keeps the previous value when the “Stop” button is pressed.
- The “F_Meter” seems to work correctly from around 30Hz up to 12.5MHz. The resolution is much better than the normal frequency reading used in “Meas” options.
     Below 30Hz the reading is erratic, perhaps due to the auto threshold detection.
     Above 12.5MHz the reading does not seem to be valid.
- The “F_Meter” will not operate correctly if the oscilloscope voltage range is set to high.

Enable the “Counter” by moving to the “ON” and pressing the “OK” button.


Notes
- The “Counter” seems to count the number of rising edges crossing the trigger level, irrespective of the rise/fall setting in the trigger menu.
- The “Counter” seems to use the same trigger level setting as the oscilloscope (Auto/Manual).
- The “Counter” increments in run mode and stops when the “Stop” button is pressed.
    Whilst in stop mode, pressing the “Auto” button does not restart the “Counter”.
- To reset the count to “0”, reselect the “Counter” from the options menu.
- The “Counter” will not operate correctly if the oscilloscope voltage range is set to high.

[Dave_g8]

Interesting, there is a recent firmware upgrade for the DSO3D12 which adds a frequency meter and pulse counter.

This appears to be a similar specification to the feature found on the DSO154Pro (HW V1.4). The DSO3D12 seems to have a higher upper frequency limit.

It may be that the feature on the DSO154Pro is also HW/FW dependant, since this seems to be the case for the DSO3D12.

[Dave_g8]

For general information, using a tinySA signal source (sine wave) terminated with 50Ω, the approximate analogue -3dB bandwidth of the DSO154Pro front end (using the supplied probe, x10 mode) is 32MHz.




At test frequencies above 20MHz, the alias frequency will be shown on the DSO154Pro, but the amplitude will be representative of the actual sampled values at the ADC.

[sims070]

I would say even buy the 2ch one for 6 bucks more with a choice day coupon.

https://nl.aliexpress.com/item/1005005953868224.html?spm=a2g0o.productlist.main.1.53bcd9c5aXJmQZ&algo_pvid=22987cd2-ff81-4434-8f3a-a8f9ae8a8f3b&algo_exp_id=22987cd2-ff81-4434-8f3a-a8f9ae8a8f3b-0&pdp_npi=4%40dis%21EUR%21174.44%2178.50%21%21%211332.59%21599.67%21%402101e64117120085714392277e985c%2112000035009715553%21sea%21BE%212723124816%21&curPageLogUid=rT1nw5orPbVX&utparam-url=scene%3Asearch%7Cquery_from%3A