New toy(?) scope Fnirsi DPOX180H, claimed 180MHz/500MSps (May 2023)

[Evi]

Is this topic about the general?

[BillyO]

Is this topic about the general?

Go find someone else to fight with. 

There have been many other scopes mentioned in this thread as well as heaps of general statements.

I realize English is not your first language, but that means you must try a bit harder to make sure your intent is properly understood.

[ru_tash]

Sorry, I recheck terminator it was bad connection (in fact all measurements were done with 1Mohm)

Retest with properly contacted.
Freq(Mhz)      1     3   10   20   40   50   60  70   80  100  110 120 130 150
Ch(Vpp,mV)   142 142 142 144 148 150 154 158 165 168  177 182 186 196

It really seems strange that the amplitude would increase with frequency.  Something is not quite right.

let's wait someone else repeat BW test with his DPOX180H.

[ru_tash]

Bravo! Now try this on DPOX180

You were not specific about which scope you meant.  It sounded like a general statement.

In any case a sine wave sweep or rise time analysis should work just fine on the DPOX180 to determine it's bandwidth.

perhaps he meant to say that some cheat/cheap oscilloscopes artificially "reconstruct" sine wave based on prediction (or without it) on higher side of BW.

[walshy007]

let's wait someone else repeat BW test with his DPOX180H.

I can do that, my DPOX180H came in the mail last week. I figured it would be a cheapish toy but if I could learn it's limits by comparing it to my 300mhz rigol it could be useful for portable use.

I'll set it up the sig gen and be back in a bit with a couple numbers for comparison.

[walshy007]

My results

The signal generator used was an ancient "turn the dial" type going to a coax output fed directly into the scope.
The amplitude dial being adjusted until the rigol read the number I wanted to check on. Coax then fed to DPOX180H, and when done back to rigol to double check what it says. All measurements peak to peak.

Freq (mhz)	3.5	30	60	90	130
Rigol	1.00v	1.00v	100mv	1.00v	100mv
DPOX180H	1.00v	0.984v	109mv	1.15v	135mv

The upwards at higher frequencies trend matches ru_tash.. which is.. weird. Definitely not just them though.

[BillyO]

Yeah, very strange.

Thanks for looking into it guys.

[IconicPCB]

If a square wave is used to check the bandwidth then upward swing is to be expected since the effective sampling rate of the front end drops off with increase of input frequency.
Now consider the fourier coefficients of a square wave and the amplitude of fundamental versus RMS/PEAK .
As signal frequency goes up, sampling rate drops down with respect to the fundamental.
This results in a  loss of higher order harmonics and so fundamental becomes more prominent.
I seem to recall 1,4 is the multiplier of fundamental. And then again it is possible the front end of the input stage may be slightlyover compensated resulting in a complex pole pair and gain peakines.

While messers Nyquist and Shannon assert  minimum sampling rate of two and the toy scopes offer a sampling rate of fivish... a real man;s scope should offer a sample rate of typically tenish for good waveform reproductive fidelity...

Try doing bandwidth measurements with a single channel active and then repeat with both channels active ( to see effect of reduced sampling rate)

[Evi]

https://youtube.com/shorts/dXxeHHcKgRU?feature=share

Better once to see.

[Rooster Cogburn]

I have found a new video showing a new bug/crash of this device when using the usb function. Try on your units to see if it happens.
https://youtu.be/NLNTrn9KVrk

I just got my DPOX180H and it seems to have the exact issue from the video The scope seems to work and I can connect it over USB on my Mac and the files/directory structure is there but as soon as I either try to upload a firmware file or download any screenshots or waveforms the unit freezes and no copy takes place. I tried on my Linux laptop and the volume never even mounts. I tried resetting all settings and formatting the storage no change. When I back out of the USB screen I get the same effect as in the video where all the text is missing.

Any ideas?

[Aldo22]

https://youtube.com/shorts/dXxeHHcKgRU?feature=share

Better once to see.

That doesn't look too bad.
In single-channel mode, however, it only becomes a sine wave at 60MHz, doesn't it?

[Evi]

Do not mix it with ZEEWELL
It does not

[Aldo22]

Do not mix it with ZEEWELL
It does not

That's hard for me to believe.
With the Zeeweii DSO2512G you can calculate it pretty accurately.
Single channel, not overclocked: 96MHz bandwidth.
So you can still see the "3rd harmonic" at 96/3 = 32MHz (Before it looks like a sine).
Overclocked 120/3 = 40Mhz and half of it in dual channel mode (16 and 20MHz respectively).
Is that really different with the DPOX180H?

[Evi]

Zeeweii in single channel mode works in alternate ADSs mode
when both ADC channels digitizes 1 input. So, the sample rate twiced.
DPOX does not has this mode.

[Aldo22]

Zeeweii in single channel mode works in alternate ADSs mode
when both ADC channels digitizes 1 input. So, the sample rate twiced.
DPOX does not has this mode.

So this is a fake? See 50Mhz screenshot.
Can somebody confirm this?

[Rooster Cogburn]

I did investigate the USB issue a bit further. I tried a different cable and different ways of accessing the storage. Same results. On Mac it always freezes on transfer and on Linux I can't even mount anything, I just see the device on lsusb.

I asked a friend with a Windows machine and there it worked immediately. We were able to update the device with the v30 firmware posted here. Still, USB doesn't work for me with that firmware either but at least I now have the bugfixes.

Never seen a USB mass storage device before that's picky about the OS/computer, seems like the USB implementation is completely broken. Would be great if they could fix that

[Rooster Cogburn]

I've been playing around with the scope all evening, sorry in advance for all the dumb questions:

- On timebases over 50ms the measurements disappear and the scope switches to rolling mode, is there any way to keep measurements for longer timebases?
- Can you reliably/instantly set one of the vertical cursors to 0? Just because of the peculiar way cursors work on this scope setting one to zero is the only way to see an absolute position for cursor two
- Does somebody find the FFT function useful? Maybe it's just me but is this basically just a gimmick?
- Is there any way to do channel arithmetic like to simulate a differential probe?
- Does anybody else have the USB mode issue I and the fella from the YouTube video have? Did anybody here try the USB connection with Linux/Mac?

Thanks

[RAPo]

I've been playing around with the scope all evening, sorry in advance for all the dumb questions:

- On timebases over 50ms the measurements disappear and the scope switches to rolling mode, is there any way to keep measurements for longer timebases?
- Can you reliably/instantly set one of the vertical cursors to 0? Just because of the peculiar way cursors work on this scope setting one to zero is the only way to see an absolute position for cursor two

Not that I know.

- Does somebody find the FFT function useful? Maybe it's just me but is this basically just a gimmick?

you can get some info (eg is there a harmonic) but basically it is a gimmick.

- Is there any way to do channel arithmetic like to simulate a differential probe?

No

- Does anybody else have the USB mode issue I and the fella from the YouTube video have? Did anybody here try the USB connection with Linux/Mac?

No problems under windows, no problems under WSL Ubuntu, no problems on a Zorin OS.

[Rooster Cogburn]

Thanks!

So I tried the USB mode on two Macs and two different Linux systems (Mate & Ubuntu) and neither worked. A friend's Windows laptop worked perfectly. FNIRSI Support says apparently only Win10 is supported. I don't think I've ever seen an USB storage device that only works on one OS let alone fails in such a spectacular fashion when connected to another OS. I guess this was only tested on like one computer with one specific USB stack or one specific USB host controller chip. I wouldn't have much confidence this even keeps working on any new Windows version/updates.

[Rooster Cogburn]

Do you keep the scope plugged into USB power at all times when it's sitting on your bench? I noticed once it's charged the power button keeps alternating between red/green every couple of minutes. I'd want to preserve battery health as much as possible and wonder if it's best to only plug in the scope when using it or when it's empty or to just keep it on a USB charger at all times.

[RAPo]

No when I am using the scope for measuring there is no USB connection. Only for charging and transferring files the usb-cable is in.

[Aldo22]

Zeeweii in single channel mode works in alternate ADSs mode
when both ADC channels digitizes 1 input. So, the sample rate twiced.
DPOX does not has this mode.

So this is a fake? See 50Mhz screenshot.
Can somebody confirm this?

@RaPo: Could you please confirm this?
You own a DPOX and you thanked Evi for his posting.
I still can't believe this as Fnirsi explicitly states differently.
Can you test with a 60MHz square wave with the second channel switched off?
For example, a NanoVNA can generate 60MHz square.

[Evi]

Thomas the unbeliever

[Aldo22]

Thomas the unbeliever

I do believe, I just don't know who!

[Aldo22]

Thomas the unbeliever

No, really. Fnirsi shows this screenshot and you say this is not possible with the DPOX180H @50MHz.
What should I believe?