Do you remember your first oscilloscope? We may have entered an era where young readers think of a luxury model with an LCD screen, but for the older among us, the image that springs to mind may be a CRT device. . I had a 1950's 2MHz broadband router, very obsolete by the 1980's, but it came to me for free. It proudly advertises as a “portable oscilloscope” but portability requires heavy weight from the owner. I still have it as a relic and a curiosity.
For most of us, a “new frame” is always a big investment. Even today's inexpensive models, like the popular Rigol instrument, can cost hundreds of dollars but offer measurement capabilities unimaginable to engineers in the 1950's, making the Jasor a coveted item.
Buyers of budget oscilloscopes may not have the money for a Rigol, Hantek, or other affordable oscilloscope. Someone starting out in electrical engineering might be looking for cheap or free used CRT models, but thanks to ever-changing technology, there is another option. Modern microprocessors and microcontrollers have analog-to-digital converters and processor cores fast enough to perform the functions of a simple oscilloscope, for which several very inexpensive "oscilloscopes and oscilloscope kits" have been marketed. They still have relatively small LCD screens and relatively low bandwidth, but since they can be had at near-affordable prices, their flaws can be overlooked in the name of value. We've been interested in this for a long time: are these tools good? For around £16 ($21) and the minimal hassle of ordering online from China, we decided to find out.
If you look at most electronic kit suppliers these days, you will find an oscilloscope kit in their range. They are mass-produced in China and the same design trends appear in different models. You can buy surface mount or through the hole and most come with a blank panel, maybe a laser cut piece of plexiglass instead of a box. However, there are one or two models that come with a box, one of which is the model we ordered. The JYE Tech DSO150 is a single-channel "oscilloscope" with a 2.4-inch, 320 x 240 pixel color LCD display with a bandwidth of 200 kHz. Its specs are similar to similar sets, although its smart casing sets it apart and makes it an easy choice.
In the box
We placed an order and when it arrived it was packaged in a small box that took a few knocks in transit but was secure enough not to damage the contents. A layer of foam protected the LCD screen, and the body parts were strong enough to protect the rest of the components. There was a discreet bag, cardboard parts, two circuit boards, a test stand with alligator clips and two instruction sheets.
When reviewing a kit it is best to start with the instructions as the quality of the kit is just as dependent on the quality of the instructions that make or break the kit. If you can't, no matter how good it is, it's garbage.
The DSO150 manual consists of two pages with high-quality double-sided color printing that emphasizes the words in the pictures. The first page introduces the kit and gives quick soldering instructions, then the next two pages walk through each step of construction. The last page contains basic user manuals, specifications and a troubleshooting guide. Our kit includes all SMD parts already assembled. If we had known the kit could accept SMD parts we would have bought this version.
Instruction steps are long in pictures and short in text, but sometimes there is very little indication of where the component is on the board. Sometimes you need to look closely at the table and figure to determine the correct position. However, the first step does not involve any soldering, just wire the motherboard to a 9V power supply and observe the LCD load in the oscilloscope program. Support is available through the forums on the JYE Tech website, which is where we think you'll go if the boot fails. A 9V power adapter is not included, you will need to find one with a 2.1mm center plug. Luckily, a wall used by an old router was a good candidate for the wait box.
Assembling the motherboard is quite easy, you just have to put the big elements like the switches and the connectors in the holes. The analog board has a switch with small holey resistors and matching ceramic capacitors, the resistors were small which made some of the color bands a bit difficult to distinguish. Bring a multimeter to check. There is a BNC connector that requires a lot of heat so make sure you have a large iron handy. Finally there is a small plate for the rotary encoder, then the front of the housing can be fitted with the main board, the analog board added and the bezel mounted. Check the internal voltages, connect the measurement clamp to the calibration output and set the square wave compensation capacitors, and the rest can be added to complete the device.
special feature
In use, the DSO150 is a simple and straightforward oscilloscope. Conventional volt/div and time base selection is fairly straightforward, and various trigger modes can be quickly selected. If you've used an oscilloscope before, you shouldn't have any problems with it. But of course the DSO150 isn't just an oscilloscope, it's a digital memory. And with 1024 sampling points, it can create a regular storage space, allowing the user to analyze the stored waveforms in detail by going back and forth between the stored points. The instructions are brief here, only a double press on the V/div or Sec/div keys allows scrolling.
Connecting the signal generator to our DSO150 explored its bandwidth. The claimed 200kHz is fairly accurate, pushing the signal generator past this point shows a deviation in the displayed amplitude. Also, the 10 µS per segment minimum limits the usefulness of displaying waveforms at these frequencies.
The DSO150 is equipped with a small test tube that ends in two alligator clips. It's a little less useful than the oscilloscope probes we're used to, although fortunately it can be used with a standard 1x/10x probe. Viewing the square wave from the test port through a standard probe shows an acute angle to the waveform so it appears there is no problem between the built in compensation and the probe. There are ways to use the standard DSO150 probe or to quickly replace the alligator clip with a specific probe type.
last thought
Hence the JYE Tech DSO150 Oscilloscope Kit. The STM32F103C8 is a fairly small area within the confines of the microcontroller it's running on. It's a useful pocket tool if you can handle a 200kHz bandwidth and a 50V peak input voltage. Its calibration depends on the crystal and STM voltage reference, but like the other specs, these become minor considerations when considering the pocket price. Add to that the software is open source and you have a great platform. If we wanted to turn it on we'd order a battery case and accompanying probe, but both would increase the price so as not to make too much noise. If you need room in your bag to add to your bench scope, if you're working at low frequencies, or if you have a young family member looking for their first scope, get this! Our test device is more used than getting dusty.
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