Very portable oscilloscope?

[jeremy]

Hi all,

I'm going overseas to france for some work this year, and I'd really like to take an oscilloscope with me. I don't really want to take a full DSO due to size and I am looking for something a little smaller in a USB oscilloscope. I'm looking for >=50MHz with >=2ch.

The Digilent analog discovery looks interesting, but at 5MHz it is a bit limiting. I have also been looking at picoscopes (specifically the 3400 series) and the Agilent USB oscilloscopes. Anyone have experience with either of these two? Can you recommend a better one? What is the software like for these devices?

Also: should I buy in AU or EU?

[vk6zgo]

Most modern DSOs are really quite small & outperform just about any USB thing.
If you buy one in Europe,you only have to carry it one way!

[VK5RC]

If you are buying 'good'  gear,  think about the warranty,  EU is a fair way away for a claim.  If the price difference is big,  it may be worth it.

[pickle9000]

Pico does do nice software.

[jeremy]

Hi guys,

I appreciate that you can get much more scope for your $ if you buy a standalone (never heard a great argument why...), but I'd really like one that I can keep in my bag whether I am travelling or not.

I didn't think about the warranty issue, may have to consider that one a bit further.

[pickle9000]

Try the software.

http://www.picotech.com/download.html

[Andreas]

Hello,

Perhaps you should spend a eye on the PicoScope 4423 (automotive). Or the standard 4424 part.
- size of a 3.5 inch external USB fixed disk (can be carried within the laptop bag)
- Supply via USB from laptop
- 12 bit true ADC resolution
- 20 MHz bandwidth (the price you have to pay for USB supply)
- 20/80 MS/s maximum sample rate (4 channels / 1 channel)
- 32 Ms Memory on board (divided through active channels).

If its still too bulky you could go for the new Picoscope 2200 which has the size of a passport.
But I have no experience with it.

With best regards

Andreas

[tautech]

If you are to cart test gear around, why not multi-purpose equipment?
A handheld DSO gives you...... Multi-meter, DSO, trend plots, USB capture/storage etc.
Offerings from Siglent and others.
Look for as much functionality as possible.

[branadic]

... not to forget to mention the Cleverscope...

But I can't recommend any of these scopes. Some essential facts to USB scopes:

- LabView based scope software is a bummer, so avoid buying a scope that uses such a GUI
- high vertical resolution (>12 bit) is in most cases useless as these scope are very noisy or do have only one vertical input range and no input attenuator
- Bandwith is limited compared to bench scopes
- don't expect fast response of such a scope, the limiting factor is the interface such as USB

[jeremy]

Thanks for your advice branadic, but I have one question:

- don't expect fast response of such a scope, the limiting factor is the interface such as USB

I've never really understood why this was the case. Sure, you can't stream the samples in real time, but even a standalone DSO doesn't just stream the raw samples to the application processor. A USB 2.0 connection is easily capable of transferring 20 or so screens worth of data per second, and all of the triggering and acquisition should be done in the hardware with local memory so as to not bottleneck on the bandwidth of the USB connection. Or is that not how these work?

I guess what I really want is the guts ripped out of my DS0152E, put in a small box and have the data pumped over USB rather than onto the display. I still can't work out why it is so much cheaper to buy a DS1000Z than a spec-for-spec picoscope, yet the rigol has a screen/buttons/ethernet/complicated ui firmware/etc and PC control software anyway

[branadic]

What Cleverscope does is reducing the number of measured points per waveform that are transfered to the computer and displayed on the screen. If you stop acquisition you can than readout the full memory depth (MegaPoints).
USB is still the bottleneck, it's a question of what strategy is worth... stream with the disadvantage that some packages could be lost or packages with the disadvantage that display update rate could vary.

That USB scopes with specs similar to a bench scope are much more expensive is just a question of sold exemplars. The market for bench scopes is even higher compared to USB scopes.

[Andreas]

Or is that not how these work?

Hello I do not know what a "Cleverscope" of branadic does. It seems to be a toy from his description. But I would not generalize one bad example to all USB-scopes.

The PicoScope 4423 has a internal memory of 32MSamples which is enough for 8 seconds sampled with 1us sample time. And it behaves as described by you or even better:

The data transfer is started simultaneous with measuring. So practically with streaming+memory I can set a aquisition time of 20 seconds at 1MS/s on all 4 channels without loosing data over a USB 2.0 interface.
So I do not feel that this is a bottle neck.
The data is now on the laptop and can be stored for documentation as raw data for later evaluation or screen shots directly on the disk.

Before choosing the PicoScope for mobile use I also checked a Agilent handheld. I usually need long aquisition times in the range of seconds to evaluate "single shot events".  So the 150k samples of the Agilent where at the lowest limit of being useful. But before I could set up the single shot from the very complicated menue (the agilent representative (FAE) was nervously looking in the handbook how to set up) the battery was empty after one hour instead of the specified 2 hours. So all together and with the nasty plastic BNC connectors I decided that the handheld is not useful for my needs.

The PicoScope which I got later gives around 4-5 hours useful operation with our laptops at work.

By the way: what do you intend to measure with the scope?

With best regards

Andreas

[jeremy]

Hi Andreas,

Sounds promising! I would like to measure digital clocks against analog outputs (MSO style). However, I really only need to look at one clock line, so no need for special digital channels. I am also interested in seeing any distortion which may show up as higher frequencies.

Add general troubleshooting tasks to the list and that would mean I need something on the order of 30-40MHz realistically (I use lots of ARM micros), although I definitely don't need many display updates per second (even 5fps would be fine). I just don't want to give up on high waveforms per second on a hardware level, and I can't think of why USB scopes should be disadvantaged in this regard.

I think I'm pretty keen on the 3404A as it is less than AU$1000 and gives me 1Gs/s @ 60MHz bandwidth with 4 channels. At least that is somewhat comparable to the DS1000Z. Or maybe I'll save up a little longer ($800 more) and get the 3405B with AWG/100MHz/32MPoint

What do you think about your picoscope compared to a bench scope?

[branadic]

I also tested a Picoscope but wasn't sure of it at all.
Nearly all USB scopes come in a crappy plastic package with less weight, so it's pretty easy to drop it down and frustration is perfect. Not what you want when you're sniffing around with your probe.

The more quality Picoscope in aluminium package are pretty expensive. And as I said, most of the USB scope have no good quality input stage with vertical division down to 1mV/div, but use higher ADC resolution instead. This results in bigger noise floor of the scopes. The input stages are not of same quality compared to a bench scope, but that's just my impression.

[Andreas]

Nearly all USB scopes come in a crappy plastic package with less weight, so it's pretty easy to drop it down and frustration is perfect.

Hello Jeremy,

I see your bandwidth needs are outside the 4423 range.

For the higher bandwidths (or by activating the AWG of some models) the power need of the scope is sometimes outside the USB port capabilities.
Some scopes support only 2 channel mode with one USB-Port or need 2 USB-Ports for supply (as I read on the data-shet of the 3404A). So you have to watch carefully the datasheets.
Perhaps you are better with one of the new USB3 scopes.
But I have no experience except with the 4423.
Software on PC is the same for all PicoScope scopes.

What do you think about your picoscope compared to a bench scope?

I thought you wanted to have a highly portable scope. So I would usually not compare a boat ancor which needs nearly a own power generator to a lightweight power saving scope.

I can only compare the PicoScope 4423 to the 1 GHZ MSO Tektronix which I have access to. (wich cost about factor 20 more than the 4423). And the serial decoding option adds 2 times the PicoScope price. (Serial decoding is included in PicoScope software). Memory depth are comparable. (The TEK has 10GS per channel/PicoScope 32GS for all channels).

Of cause the bandwidth of the Tektronix is larger which makes it more suitable for higher frequencies.
Also the screen updates are clearly faster on the TEK with dedicated hardware.

And especially when doing some evaluations or math functions (frequency measurements or rise time measurements)
the picoscope slows down more than the desktop scope. Especially when I use large memory depths which is usually the case.
The noise on power up settings are is larger on the TEK as on PicoScope. But this is more due to the MSO-feature (and the higher bandwidth) an can be reduced by appropriate settings. (But this costs additional time).

On the other side zooming and panning and measurement evaluation + documentation is done much faster on a windows based system. (especially zooming and setting the cursors exactly for measuring is really a pain on the TEK). I usually have to measure times in the range of up to 100ms with a resolution of below 10us.

Storing on USB memory of raw data needs also relatively long on the TEK. And you should never try to save .CSV data with the TEK as this will last several 10 minutes for full memory depth. On the PicoScope this is only the time for saving the data from PC memory to the file system. Screen shots are also easily made.

So all in all manual evaluation of complex signals is done much faster on PicoScope.
Standard automated evaluations (risetime, frequency peak-peak measurements ...) are better with the TEK.

The PicoScope since windows based can also be used "remotely" by remote desktop within network. The TEK does not have this option. (Ok I know that there are some newer windows based machines of LeCroy which also have this option).

Nearly all USB scopes come in a crappy plastic package with less weight, so it's pretty easy to drop it down and frustration is perfect.

Ok, thats why I ordered the "protective rubber case" for the PicoScope.
Which is unfortunately not available for the TEK.
http://www.saelig.com/product/ADE044.htm

with best regards

Andreas

[HighVoltage]

Take a look at the older Tektronix THS series, battery powered and very portable
These days, they are low cost on ebay, compared to what they used to cost
Even isolated grounds between the two channels

http://www.ebay.com/sch/i.html?_sacat=0&_from=R40&_nkw=tektronix+THS&_nkwusc=Tektronic+THS&_rdc=1

My favorite one was the THS720P, you always recognize it on the yellow printing on it