The FNIRSI DSO-TC3 is one of those amazing all‑in‑one pieces of test equipment which seem to be becoming more common these days. It offers a wide range of functions for the hobbyist or lower‑level engineer in a small and very affordable package. I’ve long been intrigued by these all‑singing, all‑dancing gadgets, so I jumped at the chance to put this one through its paces.

What Is It?

First, let’s look at what the DSO‑TC3 claims to do. It’s got a single-channel, 500 kHz oscilloscope, a 100 kHz signal generator, and a voltmeter. In addition, it can test all sorts of components: resistors, capacitors, inductors, transistors of all types, SCRs, triacs, diodes, and Zener diodes up to 32 V. It can even test DS18B20 temperature sensors and DHT11 temperature/humidity sensors and will decode and display certain IR remote controls. Anything more you want?

The DSO-TC3 comes in a plastic case 100 × 70 mm and 28 mm thick. It has a 50 mm × 35 mm screen. It has two buttons (On/Off/return and menu/OK), and a 4‑way pad for navigation. There are three MCX sockets recessed in the upper side, a 14‑pin ZIF socket for component tests, and a USB‑C socket for charging and updating. There’s also a master reset button.

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Besides the DSO-TC3, What Else Is in the Box?

Included are a x1/x10 BNC oscilloscope probe with the usual plastic-colored rings for identification, and a BNC‑MCX adapter to connect it; an MCX-to-crocodile clip lead for voltage measurement and signal generator output; a 3-way pin to test clip lead for component tests; and a USB‑A-to-USB‑C lead for charging. There’s also a neat manual in Chinese, English, Russian and Portuguese. So pretty much everything you need to get started out of the box.
When you switch the unit on, you get the main menu screen, helpfully on the last function you used. You have a choice of Oscilloscope, Generator, Tools or M-Tester (which is the component tester).
DSO TC3 Figure 1
Figure 1. 500 kHz square wave on the DSO‑TC3. Fear not, this is normal, the scope’s at its limits!

The Oscilloscope of the DSO-TC3

This offers a bandwidth of 500 kHz with a sampling rate of 10 MSPS – with 20 samples per cycle you should get a decent indication of waveform even at the upper end of the bandwidth. Vertical sensitivity is 10 mV to 10 V (or ten times that with the probe in the 10x setting), and a time base range of 10 µs to 10 s. There are Auto, Normal and Single trigger modes with rising or falling edge triggering. I’d have liked more bandwidth and another channel, but for the price of the unit these are adequate specifications and are likely to satisfy most hobbyists.

Scope Testing

I did two tests with the scope. The first was to put in a square wave of increasing frequency. Up to a few tens of kHz, the DSO-TC3 displays a creditable square wave, but above that, the sides show a distinct slope and at 500 kHz it looks more like a sine wave (Figure 1). But this is as it should be – the antialiasing filter in the DSO-TC3 is doing its job. A 500 kHz sine wave still looks good on the DSO-TC3 and does not lose any amplitude.

Detecting Switch Bounce

Some time ago, I was asked to do an article on switch bounce, and my old CRT scope was nowhere near up to the job. Eventually, I bought a new 60 MHz LCD scope with a good single sweep function which did the job perfectly. The DSO-TC3 also has a single sweep function, so I thought catching a switch bounce would be a good test of its capabilities.
The DSO-TC3 is quite up to the job. I set up a switch applying 5 V to a 1 kΩ resistor, set the scope to 100 µs per division and toggled the switch. I found that I did not even have to use single sweep mode – on normal edge trigger, the DSO-TC3 leaves the trace on screen until it’s triggered again. A typical result is shown in Figure 2.

Perfect Capture

The only thing I couldn’t do that my big scope does is to move the trigger point a bit across the screen to the right, so on the DSO-TC3 the first bounce of the switch that triggers the scope is right on the left-hand edge. But otherwise, a perfect capture, and I’m impressed.
Figure 2 DSO-TC3 detecting switch bounce
Figure 2. Switch bounce caught on the DSO-TC3

The Display

As you can see from the scope screen captures, the screen has a multitude of information about the amplitude and frequency of your displayed waveform superimposed on it. While this is very useful in many cases, it would sometimes be nice to get rid of it, and you can do this with a long press of the right navigation button.
All in all, a very capable little scope, and with all the other features of this device, it adds up to good value for money.

The Signal Generator

I fed the generator into my 60 MHz scope and checked the waveforms for various wave shapes, amplitudes, and frequencies. The DSO-TC3 offers sine, square, pulse (variable duty cycle), triangle and ramp (again variable duty cycle) waveforms. All are pure and clean, but there is some rounding of sharp transitions at the limit of 100 kHz. Not something I’d worry about too much for most of the work I do. The minimum level that the DSO-TC3 can output is 0.1 V, I’d have liked it to go a little lower. But generally a good general-purpose function generator to have in your workshop.

No Signal Tracing

Another review I read said that the generator does not work with the scope working. Well, not exactly, but when I set the generator up for a 10 kHz, 1 V sine wave and then went to the scope, I found I was getting a 1 kHz, 3.3 V square wave (the startup default) instead. It’s a pity this does not work properly. To be able to feed a signal into an equipment and trace it through with a scope is pretty useful. Maybe the next firmware upgrade could sort this out.

DSO-TC3 Tools

  • On‑Off is a continuity buzzer – it does measure resistance as well but showed 5010 Ω for a 4.7 kΩ resistor. It did not beep for that, but did on a 10 Ω resistor.
  • Voltage – 0 to 40 VDC via the IN connector on the top side (the other functions work via the ZIF socket). Only positive DC voltages can be measured.
  • DS18B20 – These well-known digital temperature sensors can be tested, and as soon as I plugged one in it indicated the temperature. It doesn’t matter which way you plug it in, either. Impressive.
  • DHT11 temperature and humidity sensor. I couldn’t get one of these in time for my tests, but if it works as well as the DS18B20 it’ll be useful.
  • IR Decode – there is a marked IR detector on the front panel, and if you point a remote at it and press buttons, it gives you a user code (which does not change and presumably identifies the model of control) and a data code which does change and indicates the code for the button pressed. Very clever, and it could be a very useful function.
  • Calibrate – you are asked to ‘Pls short probe’ but no amount of shorting probes or connectors of ZIF socket points, and various button presses, did anything. I’m keen to explore this further and have contacted the manufacturers but had not received a reply by the time I submitted this review. I’ll post any updates online.

M-Tester on the DSO-TC3

This is the component test function and works via the ZIF socket beneath the display. You have various combinations of points 1,2 and 3, and also K and A terminals. You plug in a component (or connect it with the supplied test leads) and press the OK button and after a few seconds the tester will tell you what the component is and the value. The 1% 4.7-kΩ resistor used above read 4781 Ω and a 10 Ω 1% resistor read 11.1 Ω. So not great accuracy, but good enough for quick tests. An LED is detected as a Zener diode (fair enough, as you can use them as such) but the LED does glow, and if you can’t tell the difference between a LED and a Zener, you probably shouldn’t be buying this tester! The forward voltage of the LED is shown.

Capacitor Testing

I tested a bunch of capacitors, from small pF values through to larger tantalum types, and while all were correctly identified, readings were considerably low on values less than 1 nF. ESR readings are given on larger caps, a nice touch. All transistors were correctly identified as PNP or NPN types with the Hfe shown. MOSFETs and JFETs were also correctly identified. But I could not correctly test SCRs and triacs. I did use the K-A test points – these use higher voltages and should be used for Zener diodes of above about 4 volts. I’ll investigate this further as well.

Other Notes

There is another menu (accessed with a long press of the Menu button) on which you can set functions like brightness and beep volume and language (it only has English and Chinese though) and see the firmware version. You can also update the firmware via the USB charging cable, though I did not try that.
I would have liked a proper BNC connector, at least for the scope probe. The MCX‑BNC adapter is fine, but I worry about breaking the connector on the scope if, for example, it was dropped or knocked. The DSO-TC3 comes in a foam insert in the box, and I’d consider making that into a cradle for it if I didn’t need it to be portable.

DSO-TC3 Battery Life

Battery life is good – I was playing with this unit most of a working day and the battery shows half. Out of the box, it took a couple of hours to charge.


There’s a lot to like about this little unit, primarily the price. There are a few minor drawbacks as well, but all in all I am favorably impressed. I’ve summarized the pros and cons below.


  • Price – really versatile, with a lot of features for a very good price.
  • Size – a very compact unit and won’t take up a lot of your workbench space.
  • Clear, easy-to-read display despite the small size.
  • Versatile – you can do many things with it, in one unit you’ve got a scope, signal generator, voltmeter and multi-function component tester.


Really, these are more ‘wants’ than negative points:
  • As above, I would have liked a second scope channel.
  • It would also be nice to have a touch-screen interface, but with the small screen and my big fingers, I should be careful what I wish for!
  • The generator cannot be set up and then carry on working while the scope is in use, a pity.
  • Some more conventional multimeter features would be nice – AC voltage and current in particular. But everyone’s got a multimeter, so not a big deal at all.
  • The manual is clear and understandable, but a little short on detail for some of the functions.

DSO-TC3: Close to Ideal?

I cast my mind back 50 or so years to when I was building my first amplifiers in my backyard workshop after school. I would have killed for a tester like this. But even now, when I do possess some decent test gear, I think this is a great little unit. For someone starting out or with limited space, it would be close to ideal. I can see a future for this unit on a versatile breadboard development and test system I am building. It’s small enough to fit in easily, and I think I’d only need to bring in better test equipment occasionally. As always, it’s horses for courses, but I’d very much recommend this unit.