The best way to get a true feel for a piece of test equipment is to use it to track down a real-world problem in a real-world design.
I really love the chance to review new products. Manufacturers are entrusting you with their latest hardware in the hope that you will love it as much they do. Most of the times I've been given these opportunities, I've been fortunate enough to enjoy truly pleasurable experiences and -- looking back over this review -- I am happy to say that this has been one of those occasions.
A few weeks ago at the time of this writing, a box arrived at my door with two different oscilloscopes to review from a new, little-known manufacturer called Micsig. Based out of Shenzhen, China, the folks from Micsig released their first oscilloscope in early 2013 (the tBook series), followed shortly thereafter by a handheld device with integrated multimeter (the MS series).
In this column I will be reviewing the TO202A from the tBook series of 10.1" touch-screen devices. For those who simply cannot wait until the end of the article to see my opinion, I can summarize it here by saying that the TO202A is an innovative device that I have really enjoyed using. It comes in at a nice price-point compared to the competition, while offering a great feature set. It also offers something that many other scopes do not -- it also comes in a battery powered version. For more details, read on...
I know what many readers might be saying at this point: "Hmmm, a touch-screen device without any knobs -- I am not sure that I can survive without knobs on my scope." Well, over the past few years I have reviewed a few oscilloscopes that have touch as their primary means of control, with some being supported by a set of auxiliary knobs and buttons. In this case, tBooks go all out because they don’t have any knobs to turn whatsoever.
Opening up the short (but very handy) user guide gives one a quick tour of how the device works. In order to maximize screen space, many of the controls are tucked away in screens that are accessed via a quick finger swipe. Because of the all-touch approach, the tBook offers the largest screen in its class at 10.1" with multi-touch capability.
While the touch screen demands one's attention, there are many other features to highlight, a summary of which are as follows:
- Model: TO202A
- Channels: 2 (a 4-channel model is available)
- Bandwidth: 200MHz
- Sample Rate: 2GS/s
- Resolution: 8-bit
- Input Impedance: 50Ω and 1MΩ
- Allowance for various probe multipliers
- Rise Time: <1.75ns
- Gradient display
- Memory Depth: 90Mpts
- Capture Rate: 500,000 Wfrms/s
Built in Storage: 4GB (extensible through a USB Port)
- Battery: up to 13,000mAH for approximately six hours of run time
- Price: US$1,198 (Available on Amazon and TEquipment.net)
In order to review this device, I actually put it through its paces by debugging a circuit I'm building for my RC receiver project. This circuit uses an ON Semiconductor AX5043 RFIC, but I was having issues getting the proper output from the data pin (as an aside, I almost have the problem fixed thanks to this scope).
I really love using an actual project and real-world problem to test a piece of equipment, because this really allows one to really get a feel for the device. Starting out as a baseline, I brought out my trusty, but heavy, Tektronix 2465. I found that I had a signal that was buried in a lot of noise. It is hard to see this noise in the image below, but -- sadly -- there was a lot of it.
View of the analog data packet from an 8-channel RC transmitter using a Tek 2465 scope (Source: Adam Carlson)
I was able to confirm this with the TO202A, which more clearly showed the noise with which I was dealing as illustrated below.
View of the analog data packet from an 8-channel RC transmitter using the TO202A scope (Source: Adam Carlson)
The signal in question is the analog signal of a RC Transmitter that is being received through the RFIC. Next, I decided to take a look at the 75.850MHz carrier signal to verify the performance of the scope. This allowed me to not only test the ability of the device to measure a VHF signal, but also to evaluate some of the built-in measuring tools. In this case, I used the peak-to-peak and frequency measurement tools.
Image of 75MHz carrier signal captured just after the bandpass filter using the TO202A scope (Source: Adam Carlson)
This gave me a nice frequency measurement of the signal. There are quite a few automatic measurements that can be selected from onscreen. These measurements can be accessed by performing a quick swipe from the top of the screen and choosing the measurements tab, or by simply pressing the measure button located at the bottom of the screen.
While probing around device I was trying to troubleshoot, I came across a little area that had a low peak-to-peak signal that I decided to interrogate. To my surprise, this turned out to be a very high frequency signal (around 1GHz).
(Source: Adam Carlson)
The scope was running at 2GSps. While I may have been below the 3dB cutoff point defining the analog bandwidth of the scope, it was nice that the antialiasing filters did not completely destroy this signal and allowed me to access usable information beyond the listed bandwidth. In fact, a picture of device testing by the manufacturer shows that the scope seems to be underrated with regard to its guaranteed analog bandwidth (at least for single channel measurements) as illustrated below.
This image shows the signal generator delivering a 265MHz sine wave signal with a peak-to-peak value of 350mV, while the scope is measuring a frequency of 264.9MHz and a peak-to-peak value of 346mV. With the listed analog bandwidth of 200MHz, the indicated signal peak-to-peak value should only be 247mV.
There are a few more key features to highlight on this scope. For example, it offers a baseline memory depth of 18Mpts and it maxes out at 90Mpts. Now, 18Mpts is pretty great for a scope in this product category (the Rigol DS2000A series offers 14Mpts), but to see the scope offer up to 90Mpts while still under the $1,200 price point is rather fantastic. (I feel like I need to use an exclamation point here, but I do not want to receive the same cease-and-desist order that Max got a few weeks ago.)
Another key feature is the waveform capture rate of 500,000 wfrm/s. Typical scopes in this price range are well under the 100,000wfrm/s rate, with most in the 50wfrm/s range. This particular spec, which is usually found on scopes that cost twice as much, really helps a user catch those infrequent glitching signals.
At the time of this writing, I have been able to spend about a month with this scope, testing out its features each night after work on my home project, and I feel that I've really got to know the device. While this device is very small and compact, its standout feature is its display, whose size outclasses anything else in a similar price range. This feature alone adds significant value to the device.
There are some small features that I would like to see changed in future software revisions. For example, I would love to see an improved gradient display for the waveforms. The scope does currently have this feature, but it seems that the display intensity variation between high and low is a little coarse. Also, I would love to see the trigger configuration screen move to either the left or right side of the display. The reason for this is that it can be very challenging to use the hold-off function unless one moves the signal to the bottom of the display. Furthermore, I would love to see more added to the math functions. The FFT function works, but the user does not have much control over configuring the sample size of the FFT, which -- in turn -- dictates the frequency bin size that is displayed. Having said all this, I do realize that despite my desire to see some improvements, this scope is already offering a great value for what it costs compared to other units on the market. (As an update, I have communicated with the vendor, and there is a firmware update in the works to increase the number of trigger types as well as much better control over the FFT display).
I end where I started; I have really enjoyed my month working with the TO202A oscilloscope from Micsig. I found that not having any physical controls did not hinder the experience. The user interface is well thought out, although there are a few areas that can be improved. I really want to thank both Micsig and TEquipment for helping to facilitate this review, and I look forward to evaluating their future products as come out (they have a very nice handheld unit, for example).