On the eletronics lab workbench, this week we had the DDS Waveform Generator from FNIRSI, a brand well known for delivering some products like low cost handheld osciloscopes, with a very interesting relation between features & quality vs cost.
FNIRSI DDS Waveform Generator is packed with the following features_
|DDS Frquency range (channel 1)||1HZ to 65534HZ|
|High Speed frequency (channel 2)||1Mhz, 2Mhz, 4Mhz and 8Mhz|
|Offset adjust||Yes, potenciometer 0.5pp – 5Vpp|
|Amplitude adjust||Yes, potenciometer 0.5Vpp – 14Vpp|
|DDS (Digital Digital Synthesis) signals||– Sine wave|
– Square wave
– Triangle wave
– Sawtooth wave (zig zag)
– Reverse Sawtooth wave
– Noise wave
|Interface||2 potenciometers and 5 buttons|
|Display||LCD 1602, 2 lines with backlight|
|Frequency increments||1Hz, 10Hz, 100Hz, 1000Hz e 10000Hz|
|Output impedance||20 to 200Ohm|
When I started the tests, my opinion on this device was serious affected by the performance, but with the time and as I get aquainted with the device, altough the weaknesses were visible when compared with a more advanced function generator, we can’t never forget that this is a device that costs about $15, so I decided to give it some slack improved my opinion about it.
The function generator allow us to test different 8 functions (7DDS + 1 HS), starting by sine wave, square wave, triangle wave, sawtooth, reverse sawtooth, ECG and noise, for last we have a High Speed frequency square wave with the 1Mhz, 2Mhz, 4Mhz and 8Mhz frequecies.
An interesting feature is the ability to memorize the parameters we used on our last usage, even after we power off.
In terms of frequency, the DDS function generator is able to work between 1Hz and 65534Hz (65Khz), noticing that, in frequencies closer to the limit, the problems in the signal are noticeable and we get a lot of distortion and noise in waveform.
The High Speed square wave is almost useless, being visible on the oscilloscope at 1Mhz but with a lot of deformation, but from there to higher frequencies only gets worse.
The device has two BNC channels, the first one (down) is for DDS signals and the second (up) is reserved for the High Speed signal.
The potenciometers allow us to adjust the offset and amplitude of the generated waves, naking it possible a fine tune in the outputed signals.
THE POWER Supply must be set a 9v, less than that (5V) will generate unpredictable results and more (12V) will cause an hissing sound probably because of some components overload.
In my opinion this is a typical “it depends” case, and it depends of what? Well of the usage that you will give to the function generator. This opinion is based on the premise that here we all are curious hobbyists and eager to learn, as am I, and the following hypotesis are based on this idea, not considering professionals that probably will have a much better equipment on their workbenchs, so with this premise, I see three use cases:
- In the first use case, is that guy (or gal) that has an osciloscope and use it a bit, but more for fun, to see how sine waves work and so on, and use it to learn a bit more about eletronics, some testing, nothing too serious and to give a “smart” vibe to the friends that visit, putring the oscilloscope with some sine waves. In this case, a module that costs $1,5 to $4 will be more than enough.
- The second use case, is when we are more serious about our learning, we use the oscilloscope in several of our projects to test, we fit perfectly in the use case 1, but we want a more robust solution with more options to customize what we do and even, who knows, apply the function generator in some project testing or development, in this case this device will do quite welll what you’re looking for.
- In third use case, is someone more like me, want to do serious learning and want to develop more serious projects, although, we are not talking about professionals, just for learning and you might even use the function generator in some of your projects. In this case, in my opinion I will save the $15 and sum some more $30 and buy a bench function generator, you’ll have some bench generators 5Mhz, 6Mhz and even 24Mhz starting at prices avout $50, I’ll leave the links bellow. Although these are very entry level bench function generators when compared with for example a Rigol DG1022Z (an entry waveform generator from Rigol), the quality will be much better and you’ll have a ton of functions not available in this device.
Here at TechCorner.TV eletronics lab, I choosed the Rigol DG1022Z as I mentioned before, is a entry level arbitrary function generator, with some professional quality and features.
Is my believe that test equipments, like tools in general, should be bought always considering a relation between cost, quality and features, but never use the price as prime decision factor. Those equipments if correctly used have a duration of many years, so it is a investment for long run.
But even so, the choice of this equipment even with some RIgol promotions that will allow me to have a considerable discount and using my employer, so won’t have to pay taxes (VAT), will cost me 293€ and the decision to spend this amount of money is related with the fact that I have TechCorner.TV website and channels and want to use this equipment to test other equipments in the future and also use it in some projects.
In a normal “hobbyist” situation, I’ll probably will stay with a solution like this DDS function generator or with a solution mentioned in option 3 above. Not always we can or have this amount of money to invest in a test equipment, that even if we have it, will not certainly be a good investment if you don’t have use for it, it will be a very expensive paper holder.
In short, this device gives us what we paid for, it is a cheap device, of minimal quality for what is intended, but it does the job, providing us with a few different waves that allow us to test various situations.
So here it is some alternative devices for lower and higher budgets:
- Modules (DYI)
- https://s.click.aliexpress.com/e/_AYcJum – ICL8038 Signal Generator Synthesizer Function Square Wave Signal Generator Module Pulse Frequency Electrostatic Synthesizer DIY (3 different types available)
- https://s.click.aliexpress.com/e/_AkmpxM – XR2206 Function Generator Kit Square Wave Signal Generator Module 1Hz-1MHz Adjustable Frequency Pulse With Cover Box Protect
- Low cost function generators
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