I’ve been spending some time with a low-cost PicoScope device, and wanted to give a review in case you’re looking at one. To begin with, you can check out my Circuit Cellar Articles about selecting a scope.
There’s also a video version of this:
Introducing the 2200 Range
PicoTech’s 2200 range is a compact oscilloscope, if you want all the details check out The PicoTech Website. Presumably you’re interested in my hands-on experience instead though, so I won’t duplicate everything there.
The one great thing about these is the small size – here’s mine mounted below my desk, ready at a moments notice! Even if your desk is 100% full of stuff you are debugging, you just need to plug a probe in (also has BNC dust covers in this photo, I got from E-Bay).
I’m going to be looking at the 2204A in particular, which is the lowest-cost device (~ $160). Even at the $160 price this device is made in the UK, which is extraordinarily impressive!
There is a bunch of devices in the family which at first glance appear to mainly change based on bandwidth, sample rate, and sample buffer size, although there is some other details you should check into.
In particular note that a number of ‘baseline’ specifications are split into two camps: the 2204A/2205A, and the 2206A-2208A. Compared to the 2204A or 2205A, the 2206A-2208A add a faster AWG output maximum frequency (1MHz vs 100kHZ) and add the ability to have an analog offset subtracted from the input voltage. There’s a few other changes too, but those are the two that might most convince you to get something like the 2206A.
Again for a bunch more details on bandwidth and whatnot see my Circuit Cellar Article, or the PicoTech 5000/6000 review also posted on this site. I just wanted to make a quick note about the bandwidth & marketing.
The 2204A I’m reviewing lists only a 10MHz bandwidth, which you might seem is too slow. But note that the sample rate is still 100MSPS – many low-cost companies will sell you a scope with 2x the sample rate as the bandwidth, thus if you look on E-Bay a 100MSPS scope will have a 50MHz bandwidth. This is almost undoubtedly going to get you into trouble, since the only thing you can measure at 50MHz is a pure sine wave. Anything else (which will have harmonics) will probably cause aliasing, since the anti-aliasing filters are never that good.
These devices even feature the Equivalent Time Sampling (ETS) mode, which gives you up to 2GS/s for my little 2204A! You’ve still got a limited bandwidth, but you can use that 2GS/s mode for things like phase shift measurement with very high resolution.
Probably one of the best aspects of the PicoTech stuff is the software. Since they use the same software across their entire product line (e.g. their $7000 scopes use the same software as their $160 one), you’ll find way more features and more updates than companies that have segmented their software releases.
This $160 scope can use the digital decoding of serial protocols for example, which like any other scope includes CAN, LIN, I²C, UART/RS-232, SPI, I²S, and FlexRay. Again when comparing scopes be sure to check what you are getting, since a lot of off-brand scopes might just have UART or similar!
I won’t go over too many details of the software since I covered this in previous reviews of the 5000/6000 device, and there’s a little bit in the video at the top of this page.
There’s also a Python library for using this device in scripts – see GitHub.
One of the main downsides of this scope is the small buffer size, but it’s basically standard for the price-range. I think it’s explicitly worth mentioning this though so you aren’t surprised when you try out the scope!
At 100MS/s for example, the 8kS buffer means you could record 80uS of data, so you can’t do a lot of ‘searching’ away from your trigger. Having a larger buffer is one of the reasons for considering to move up a little in this range (e.g. the 2206A perhaps), or even to a larger device. Check out my 5000/6000 review and the Circuit Cellar article for some examples of what you can do with huge buffers.
(Click on the first 3 photos for a big version)
Removing the four screws on the bottom side gives you something like the following. Note the outside casing is actually recyclable(!). The grey piece is a shield that folds around the system.
Here is the main board (be sure to click for all the glory). A small FPGA is used for both logic & data buffering. Remember this unit *retails* for about $160 USD, which seems cheap once you start adding up everything involved! Anyway the main ADC is an Analog Devices AD9288-100. It’s rate at 100MS/s, which is the maximum for this scope. PicoTech is not overclocking the devices which is always nice to see, so should get very good performance. The bigger blocks are relays mainly, which I assume are used for switching ranges/coupling modes.
On the backside you can see the manufacture of the PCB listed as ‘ZOT’, I assume this is the zot.co.uk company. Amazingly this device is built in the UK, still for the $160 price point!
You can also see some of the internal layers, and see the clearances around the input stuff to keep stray capacitance down:
As mentioned the recyclable casing, something I guarantee you the low-cost ebay scopes won’t have!
Out of interest I wanted to look at the probes that you can get with the 2204A (the 2204A doesn’t come with probes by default, the others in the series do). I’m going to compare that probe to a cheap one I bought from Ali-Express – this probe seems to come with all the ‘random brand’ scopes, as almost every low-cost scope you see on E-Bay has probes that look the same. This second probe will henceforth be called the “E-Bay Probe”.
The PicoScope probe isn’t anything too special (e.g. it’s not nearly as high quality as probes coming with their better devices), but how does it compare to probes that you get with other cheap devices?
The cheap E-Bay probe is on the left, the probe that comes with the 2205A-2208A is on the right. The E-Bay one comes with the colour rings which the PicoTech probe doesn’t come with, but that’s about the only victor it scores.
The grabber is a stamped metal on the E-Bay probe, the PicoTech probe has a bent wire. The bent wire seems to grab test-points more reliably, although the stamped metal worked well to grab bare wires (mainly due to it’s sharp edges).
The ground connection for the E-Bay probe uses this stamped metal connection, which is hard to remove, and easy to rip off the wire. Not ideal:
The PicoScope probe uses something like spring steel to make this group clip, which also has a nice strain relief. I had much less hassle with this:
A bit of a surprise: the E-Bay scope used the strain relief crimp inside the group alligator clip to ‘crimp’ the ground wire! It’s a pretty crappy connection, since it’s not designed to be used as an electrical crimp!
I was happy to see the PicoScope probe was soldered, so should be a little more reliable.
This device also has an arbitrary waveform generator. You’ll probably use it most of the time in non-arbitrary mode (e.g. sine, square, etc), although the arbitrary mode is handy for some tasks like replaying a waveform such as a serial packet, and even changing the voltage and timing.
The output voltage is limited – you’ve only got 2V peak-to-peak. This means you can have a 0-2V waveform for example, so don’t expect to use this for digital 5V logic systems!
But for analog stuff (or even lower-voltage logic) it’s great. There’s even a fixed output mode, so you can use this as part of something like setting an amplifier gain. Remember there is a Python interface to the scope, so you can start doing stuff like having a (slow) control loop implemented via software!
It does also feature a sweep mode, so you can use this to characterize frequency response of systems by using the sweep mode + the FFT in peak-hold mode.
Final Review & Notes
One thing I haven’t mentioned yet is that the small size is really extraordinarily handy. This is the perfect scope for travel, so even if you’ve got a full-size scope this one is a great addition! You can also use it easily with something like a laptop or even a Surface Pro, giving you some real portability.
The main disadvantage of this scope is the smaller buffer size, although again considering the cost you won’t do a lot better.
Compared to the ‘off-brand’ scopes on E-Bay that look similar, this PicoScope is miles ahead. In particular some of the off-brand scopes have pretty limited software, compared to the full-featured PicoTech software. And this device is even made in the UK!
Also as mentioned don’t get tempted away by higher analog bandwidths, when the sample rate is only 2x the bandwidth. It can be a little hard to directly compare the competing options, so look over things carefully!
If you’re looking at the lower-end devices, consider if you can move up to the 2206A. As mentioned this gives you a higher maximum frequency on the signal generator along with the offset adjustment. It’s up to you if it’s something you actually need of course, if you’re only doing audio-frequency stuff it might be a waste.
Overall it’s a great line of devices, and in particular it’s nice to have the compact size for travel & storage. I haven’t run into any problems with them, but will update this if I do.