VOLTCRAFT DOV series

[Aldo22]

So I'd say, yes, for €200, this is a good to very good device.
But basically, I would recommend that everyone wait until they’ve saved up enough money to buy the current gold standard in small 12-bit oscilloscopes.

I haven't received the DOV702 yet, and I've never tried the SDS800X HD or the DHO800, but based on the information I have, I completely agree with your assessment.

My point, however, is slightly different.
While it’s tempting to compare the DOV700 to the models mentioned above based on its features and specs, at its current price, the DOV702 really needs to be compared to scopes like the FNIRSI 1014D or the Hantek DSO2000—and there’s a world of difference between them.
The DOV702 definitely represents the next generation, and the other budget models don’t stand a chance anymore.

Here are some features and specifications that are better than, for example, the somewhat outdated DSO2000—not to mention the FNIRSI:

- 1024 x 600 touchscreen with intensity/color grading.
- 12-bit
- 50M memory depth.
. 500 µV/div
. 50,000 wfms/s – 700,000 wfms/s
- Network connection / Web Control
- HDMI
- Mouse / keyboard option
- Built-in web browser
- Advanced math functions, 1 Mpts. FFT with peak display
- It can be powered by a power bank.
- etc.

This is unmatched in the 150 euro price range, and that’s the point, in my opinion.
Hantek and Fnirsi currently have nothing to counter this.
But what Conrad is doing here smells a lot like a ruinous price war.


P.S.
To be fair, though, I have to admit that the Hantek DSO2000 does have a few advantages over the DOV700.

- It can automatically measure up to 300.000 MHz.
- It has an external trigger and a line trigger.
- It has an AWG that is quite useful in some respects, with good rise times for square waves and AM/FM.
- And last but not least, it’s completely silent. 

[Performa01]

... And it is also useful to know that the internal/digital combine is expected to offer similar results.

Only for low frequencies. At higher frequencies, starting at 10 MHz or even earlier, the generated intermodulation products become significant - of course only for devices that perform a little better than what we've seen here so far. The reason is that the digitally synthesized two tone signal has to pass the output stage of the AWG. Basically, we are seeing the nonlinearity of a high speed OpAmp, which has to deliver enough power to drive a 100 ohm load. This will not have very low distortion at high frequencies, when the loop gain is low.

[Martin72]

@Aldo22:
I've emphasized that several times as well.
At the current price, it's a good deal.
But:

But what Conrad is doing here smells a lot like a ruinous price war.

Conrad isn't a manufacturer looking to start a price war; it's a retailer trying to clear out its inventory.
There could be several reasons for this, ranging from clearing out old stock to having too many returns...

[Aldo22]

Conrad isn't a manufacturer looking to start a price war; it's a retailer trying to clear out its inventory.
There could be several reasons for this, ranging from clearing out old stock to having too many returns...

Sure. I'm just wondering why they're offering these huge discounts only in Germany and Switzerland.
conrad.com, conrad.at etc. still have the regular prices, which are not very attractive.

[Filippo52]

Meanwhile, it's increased by almost €40, now on https://www.sotel.de/
it costs €218.65, and that's the site where it cost €179.10 until two days ago.
Filippo

[Aldo22]

Meanwhile, it's increased by almost €40, now on https://www.sotel.de/
it costs €218.65, and that's the site where it cost €179.10 until two days ago.
Filippo

At Völkner, the price is still the same.


My DOV702 should arrive tomorrow.

[Martin72]

Mine too...

[Lutz21]

I purchased the DOV704 from Völkner (179,10€) and can confirm the following problems so far:

- offset on all channels up to 2 mV, drifts with fan speed
- ripple on the positive half of the calibration output
- ripple in the 200 mV/div range

By hitting the default button after 30 minutes and seflcalibration the offset is gone on my device.

[Martin72]

- ripple on the positive half of the calibration output
- ripple in the 200 mV/div range

So it seems to be a recurring issue; I’ll probably know for sure tomorrow evening.
But I won’t be sending it back again; I’ll try to find out where this ripple is coming from.

[egonotto]

Hello,

Could someone please show and measure the noise on channel 3 with a bandwidth of 20 MHz at 1 mV/div and 1 ms/div, and with enough memory to allow for the maximum sampling rate?

If possible, with a 50-ohm terminating resistor.

Best regards,
egonotto

[Martin72]

As you may recall, on these oscilloscopes, anything below 5 mV/div is automatically limited to a 20 MHz bandwidth.
But Egonotto, why channel 3 of all things?

[Aldo22]

Well, it's here! 

A few first impressions.
The package from Conrad was ridiculously huge.





The Android stuff is pretty intuitive and works well.
Network, flash drive, and a small wireless external keyboard with a touchpad—no problems.
Then I immediately read eevblog on the oscilloscope. 






The ripple at 200 mV / 2 V is also clearly visible on the two-channel version.

The noise at 500 μV looks like this (Acq “normal”):



And with light averaging (2), like this:





So far, I think it’s pretty fun. Too bad about the small ripple at 200 mV / 2 V.

The fan isn’t loud, but it’s a bit annoying.

More later...

[Lutz21]

Hello,

Could someone please show and measure the noise on channel 3 with a bandwidth of 20 MHz at 1 mV/div and 1 ms/div, and with enough memory to allow for the maximum sampling rate?

If possible, with a 50-ohm terminating resistor.

Best regards,
egonotto

ok, I try to upload the first image - channel 3 with 20 MHz at 1 mV/div, 1 ms/div and  50-ohm terminated

[Martin72]

So it seems to be a recurring issue; I’ll probably know for sure tomorrow evening.

The package is delayed.

[Aldo22]

Since I rarely, if ever, need 4 channels, I decided on the DOV702.
But also because I thought I could connect the Voltcraft and the Hantek together for triggering.
The Voltcraft has a trigger output and the Hantek has a trigger input.

It works very well. 

In the image, I have a single, manually triggered pulse (50 ns). The Hantek is set to external trigger and “normal” mode.
There’s a slight, constant delay that you can correct, and then it works great.
The Voltcraft waits for the pulse in single-shot mode, and the Hantek follows along.
So you can trigger 4 independent channels together this way.

And you can see more than on a single screen.... 

[2N3055]

The whole benefit of multichannel scope is capability to see many signals on the same screen to be able to see and measure their relative timing and such. Having 2 2 channels scopes is not the same... Just saying..

[Aldo22]

The whole benefit of multichannel scope is capability to see many signals on the same screen to be able to see and measure their relative timing and such. Having 2 2 channels scopes is not the same... Just saying..

Why can't I do it that way?
If they trigger at the same time, I can compare the times, right?
Of course, it's a bit more tedious.

But like I said, I don't think I really need that.

[Martin72]

When one scope triggers the other, there's a slight delay between the two scopes—not huge, but it's there.

[2N3055]

The whole benefit of multichannel scope is capability to see many signals on the same screen to be able to see and measure their relative timing and such. Having 2 2 channels scopes is not the same... Just saying..

Why can't I do it that way?
If they trigger at the same time, I can compare the times, right?
Of course, it's a bit more tedious.

But like I said, I don't think I really need that.

The point is to have them all on the same screen, same instrument. Then with measurements and cursors and math you can inspect details.
Just having some squiggles on separate screens is not the same. It is not useless, but it is far from being the same thing.

If you don't need it then you don't. That is a different thing.

OTOH, if you just need to monitor some separate, non related signals for existence or general shape (like several different, non synchronized oscillators or whatever) then you might find useful to have 4 separate single channel scopes so you can have each on different timebase or other settings (like one in Roll mode, one in X-Y and 2 at different timebases.....

Tool for the job.

[Aldo22]

When one scope triggers the other, there's a slight delay between the two scopes—not huge, but it's there.

Yes, I mentioned that above.
But this delay is constant.
You can compensate for it by adjusting the horizontal position.
You can measure the differences using the cursor.
Of course, it’s not very convenient, but if you only need to do it once in a blue moon, it’s doable.
The important thing is that the VC and the Hantek trigger or stop at (almost) the same moment.

[Aldo22]

A few more impressions:
300 MHz
80 MHz square wave
1.4 mVpp
FM
AM

[egonotto]

As you may recall, on these oscilloscopes, anything below 5 mV/div is automatically limited to a 20 MHz bandwidth.
But Egonotto, why channel 3 of all things?

Hello,

Thanks Lutz21.

I had the impression that Channel 1 was particularly bad due to the approximately 7.5 kHz interference.
I was hoping that Channel 3 would be significantly better. Unfortunately, that doesn't seem to be the case.

Best regards,
egonotto

[egonotto]

Hello,

When I tried using the trigger output as a trigger signal for a second device, I noticed a delay that wasn't constant. There was jitter and a very strong dependence on the time base.

Best regards,
egonotto

[Aldo22]

Hello,

When I tried using the trigger output as a trigger signal for a second device, I noticed a delay that wasn't constant. There was jitter and a very strong dependence on the time base.

Best regards,
egonotto

Yes, there is some jitter, but it's acceptable up to about 200 ns/div.
In the attachment, you can see the Hantek, which is externally triggered by the Voltcraft.
I turned on persistence so you can see the jitter. I don't think it's that bad.
The offset is also constant for me.
But anyone who needs this for professional use should definitely look for other solutions.

[Martin72]

Basically, you can only measure a time delay between the trigger input and the trigger output.