New handheld/desktop DSO+DMM, Fnirsi 2D15P, 100MHz/500MSpS (september 2025)

[sizziff]

I don't think this is an insertional "fudge" as it's working the wrong way.  The waveform is a truer representation over the 4.2MHz.  I really believe there is something erroneous going on here.  They are not turning things into a sine wave and the rise time above 4.2MHz is far more accurate than the rise time below 4.19MHz.


@sizziff: The transition actually happens over about 10kHz.   From 4.19MHz to 4.2MHz, and it happens transitionally.  By that I mean at intermediate frequencies it switches back and forth between the two slopes.  Also, I think a lot of the "ringing" you are seeing is because you are not terminating the cable from your generator with 50 ohms at the scope.  Look at the images I've attached.  Using a 50 ohm pass-through the "ringing" you see is gone.

The ringing on my screenshots is caused by a very fast signal generator, with a rise time of around 0.6 ns.

And by the way, all the measurements shown in the video and on the screenshots were made with a 50 ohm pass-through terminator connected at the oscilloscope input.

The ringing is not ideal, of course, but considering the price of the 2D15P, I don’t really have any complaints about that.

And by the way, the strangest part of all this is what happens when the 2D15P switches into this crazy mode: look at how the interpolation reacts to a fast signal.

Just look at that sawtooth/comb-like pattern on the edge — that is completely beyond normal behavior. 🙂

[ataradov]

The “sine wave” that is often seen at the upper frequency limit is usually the result of sinc interpolation. Almost all digital oscilloscopes that use sinc interpolation do this. Sinc interpolation itself is not the problem.

Except for Fnirsi it happens at a certain measured frequency and will oscillate from dirty to clean if you vary the frequency just a bit.  It happened on severely under-powered handheld scopes where they provably lie about sampling rate anyway.

But with the 2D15P, something else bothers me. At frequencies above about 4.2 MHz, it displays the signal relatively adequately, but when the frequency is reduced to only 4.1 MHz

I'd guess this is an unexpected side effect of some of their fudging attempts.

[BillyO]

Just look at that sawtooth/comb-like pattern on the edge — that is completely beyond normal behavior. 🙂

Do you remember the chop/alternate modes on analog scopes?  It kind of looks like they are moving from chop mode to alternate mode as they pass above 4.19MHz.  Just a wild guess, but maybe they are doing something like that to take best advantage of the available sample rate.  But they made 2 errors in the implementation 1) It should have been at about 4kHz, not 4MHz.  2) It should only be done if CH.2 is enabled.  Like I said, just a wild guess.

I'd guess this is an unexpected side effect of some of their fudging attempts.

Why don't we investigate this with FNIRSI a bit further before we instantly jump to the conclusion they are doing something sneaky.  The "problem"  (not that it was a real problem) you mention was found on one singe scope quite some years ago.  No further cheating has been verrified since.

[sizziff]

Just look at that sawtooth/comb-like pattern on the edge — that is completely beyond normal behavior. 🙂

Do you remember the chop/alternate modes on analog scopes?  It kind of looks like they are moving from chop mode to alternate mode as they pass above 4.19MHz.  Just a wild guess, but maybe they are doing something like that to take best advantage of the available sample rate.  But they made 2 errors in the implementation 1) It should have been at about 4kHz, not 4MHz.  2) It should only be done if CH.2 is enabled.  Lie I said, just a wild guess.

I have about six FNIRSI scopes, including the infamous 1014D, and none of them have this particular problem.

For example, the DPOX180H displays signals quite well for its price, without this kind of strange behavior.

As for the 4 kHz idea — I actually like it. That sounds like a plausible explanation: maybe some kind of mode switching logic was intended for low-frequency/dual-channel operation, but in the 2D15P it somehow triggers around 4 MHz instead.

[BillyO]

FNIRSI products come from different contract designers.  I wouldn't expect to see similar approaches across all products.

The 2D15P seems to be quite a departure in many ways from previous efforts.

[BillyO]

Below is the response I got so far from FNIRSI.  I hope everyone is submitting a report.

If I do not hear back from them within 2 weeks, I'll request an update.

Hi Bill,

Thank you for your detailed feedback and for providing the screenshots.

We understand your concern about the difference in the displayed rise time around 4.19MHz–4.20MHz. We will forward this issue to our testing department for reproduction and further analysis.

If we confirm that this behavior is caused by a firmware issue, we will work on correcting it and release a new firmware update in the future.

Thank you again for bringing this to our attention and for your recognition of the 2D15P. Your feedback is very helpful for improving the product.

Best regards,
Technical Support Team
FNIRSI

[smk]

And by the way, the strangest part of all this is what happens when the 2D15P switches into this crazy mode: look at how the interpolation reacts to a fast signal.
Just look at that sawtooth/comb-like pattern on the edge — that is completely beyond normal behavior. 🙂

Does the 2D15P show the same behavior when it is working in single trigger mode?

[BillyO]

Yes, it does.

[BillyO]

Below is the latest from FNIRSI.

I will keep at them, but it would help if I lots of help.

Hi Bill,

Thank you for following up.

We understand that this issue is serious, especially since it may affect rise/fall time observation and waveform display accuracy.

Your feedback and test information have already been forwarded to our software testing team for further verification.

If the problem is confirmed, it will be further escalated to our R&D team for analysis and firmware optimization. At this stage, we are not yet able to provide a confirmed fix or release date, but the issue is already under internal follow-up.

We apologize for the inconvenience and appreciate your patience while our team continues checking this.

Best regards,
FNIRSI Support Team

[BillyO]

Again, the latest from FNIRSI

Dear Bill,

We sincerely apologize for the delay and for not providing you with a timely update.

Our testing team has successfully reproduced the issue and has forwarded the findings to the R&D team for further analysis and resolution. We understand that this problem is serious and may affect your decision to recommend the product.

At present, however, we have not yet received a confirmed repair schedule or firmware release date. We will continue to follow up internally, but we do not want to provide an estimated date before it has been officially confirmed.

Thank you for your patience and for your positive comments about the instrument despite this issue.

Best regards,
FNIRSI Support Team

It seems they have finally reproduced the problem.  Now I guess it's a matter of whether they can get the design team to respond.

I honestly like this little toy otherwise.  With this problem fixed I think it it would be a really useful tool for the price.

[ahmad_k]

I bought this yeaterday and noticed a big issue with noise when the vertical ref is set to the middle of the screen. A huge noise appears. No matter what probe I use and no matter what signal generator I use. I always see those spikes on 0. If i scroll up or down the signal, the noise disappear. Can anyone try this please ? I am returning the unit and requested a refund. I just want to know if it is a model bug or my unit is defective.

[BillyO]

I don't seem to have that problem.  What firmware are you on?

[ahmad_k]

I see your signal is a little above the zero. Can you please make at 0 and see if the noise will be visible ?

I was on 2.0.0.7 then I tried the latest firmware

[BillyO]

No, the noise is never visible.  I tried on zero and 1 step above and below the line.  It's not doing this.

I've added another using an external sig gen too.

[ahmad_k]

Then I have a defective unit. Thank you

[aristak]

Hi everyone, there's a new firmware version. 2D15P Firmware V2.7.0.7 https://www.fnirsi.com/pages/manuals-firmwares?srsltid=AfmBOoqujQs9yErPKK-0eC3OFvD1gpdj6aZZn37wIz4T5rvbGM_cB_d7

[aristak]

[ VERSION DESCRIPTION ]
- Fixed a bug where a watchdog reset would occur when taking a screenshot on the multimeter or signal source interface after taking one on the oscilloscope interface.
- Fixed a bug causing display anomalies on certain screens during SFC writing.

[BillyO]

Unfortunately it does not fix the rise time problem.

I think it's time to give up on FNIRSI.

[BillyO]

I've noticed another issue.  It may be limited to mine, I don't know.  Anyway,  there seems to be a very high parasitic draw on this.  Despite the largeish battery, it will only last about 3 weeks on the shelf before the battery is 95% depleted.

Is anyone else seeing that?

[ataradov]

Looks like individual device issue. I just returned from a 3 week vacation, so it was at least 3 weeks since last charge. In practice it was likely months. I just powered it on and the battery is full.