What is the practical use of a function generator ? - Page 1
Forum section: electronics / beginners

author: ArchieAltz
author_rank: Contributor
timestamp: January 06, 2025, 02:13:51 pm
content: I've been interested in making my own function generator or buying one off the internet , I am aware that in theory it is used to create multiple different types of waveforms on different frequencies etc.However everywhere I've looked at lists vague reasons on what it is used for practically . If someone could help me understand it better and perhaps recommend some begginer function generators I'd be very thankful :-)

author: Terry Bites
author_rank: Super Contributor
timestamp: January 06, 2025, 02:18:12 pm
content: Homework?

author: ArchieAltz
author_rank: Contributor
timestamp: January 06, 2025, 02:20:03 pm
content: Quote from: Terry Bites on January 06, 2025, 02:18:12 pmI guess it could be used for homework

author: SteveThackery
author_rank: Super Contributor
timestamp: January 06, 2025, 02:29:16 pm
content: I'm no expert, but I use my signal generator in conjunction with an oscilloscope in the following ways.I use sine waves:1/ When I'm checking the frequency range over which a circuit operates.2/ When looking for gross distortion, such as crossover distortion.3/ To check the maximum input signal a circuit will handle before clipping.4/ To check that clipping is symmetrical.5/ To look for the asymmetric soft clipping that is typical of valve amps (it produces even harmonics), as it is popular with guitarists.As for square waves:1/ I adjust the mark to space ratio so it looks like a series of pulses and use that as a clock signal when prototyping digital circuits.2/ I zoom in to measure the slew rate and rise time of a circuit when it is driven by a square wave.3/ I look for any ringing that might occur after each up or down transition.4/ A square wave shows a characteristic shape when it is passing through a high-pass or low-pass filter, so it's a quick and dirty way to get an idea of what's going on in a circuit regarding filtering.Saw tooth waves:So far I haven't found much use for a sawtooth wave.Arbitrary waveforms:As a hobbyist I have yet to find a use for arbitrary waveforms.

author: bostonman
author_rank: Super Contributor
timestamp: January 06, 2025, 02:30:01 pm
content: It's more for universal use such as needing to inject a frequency into a circuit you made, maybe you're repairing something that isn't producing a waveform, so you inject your own to troubleshoot, etc...When you design something, or at least me, you start with the hardest part of the design. You already know an oscillator producing 10MHz exists, but not sure your design will work. Rather than buy the oscillator, start by producing your own.I have a few function generators and they've come in handy a few times over the years. If you're questioning to purchase one because you think it's used all the time, your money is best spent on multimeters and oscilloscopes.

author: ArchieAltz
author_rank: Contributor
timestamp: January 06, 2025, 02:31:17 pm
content: Quote from: SteveThackery on January 06, 2025, 02:29:16 pmThanks this is very good information . What kind of specs does your signal generator have ?

author: brucehoult
author_rank: Super Contributor
timestamp: January 06, 2025, 02:46:41 pm
content: Quote from: ArchieAltz on January 06, 2025, 02:13:51 pmSDR or bust!

author: ArchieAltz
author_rank: Contributor
timestamp: January 06, 2025, 02:50:41 pm
content: QuoteWhat does this mean ?

author: SteveThackery
author_rank: Super Contributor
timestamp: January 06, 2025, 03:12:12 pm
content: Quote from: ArchieAltz on January 06, 2025, 02:31:17 pmMine is the famous JDS6600, which was very popular with hobbyists. You can google up the specs for it (and I suggest you do because it would clog up this thread if I tried to post it all here).I bought mine quite some years ago, so there may be other products these days which are better. The frequency accuracy is +/- 20ppm, which is absolutely good enough for me, but is probably something that has been improved upon in more modern instruments.Take a look:https://joy-it.net/en/products/JT-JDS6600EDIT: This is the user manual - it gives you the best description of the various features:https://joy-it.net/files/files/Produkte/JT-JDS6600/JT-JDS6600-Manual-2020-02-07.pdf

author: armandine2
author_rank: Frequent Contributor
timestamp: January 06, 2025, 03:14:07 pm
content: Quote from: ArchieAltz on January 06, 2025, 02:20:03 pmhow about this one? None of this is overly intuitive, unfortunately.

author: ArchieAltz
author_rank: Contributor
timestamp: January 06, 2025, 03:21:43 pm
content: I have already gotten myself a multimeter and a decent enough digital oscilloscope that's why I am asking around for a function generator

author: rstofer
author_rank: Super Contributor
timestamp: January 06, 2025, 04:33:50 pm
content: Some function generators can draw a Valentine's Day heart on a scope. This may help justify having a bench full of TE to the significant other:https://www.eevblog.com/forum/chat/a-valentine_s-day-activity-for-your-scope-and-function-generator/

author: ArchieAltz
author_rank: Contributor
timestamp: January 06, 2025, 05:08:44 pm
content: Quote from: rstofer on January 06, 2025, 04:33:50 pmI don't have a gf lol . I need to justify this to myself since I am buying it with my own le money

author: tszaboo
author_rank: Super Contributor
timestamp: January 06, 2025, 05:10:45 pm
content: Making arbitrary clock or digital signals for testing ICs.Making bode plots.Testing amplifiers.Using it as a setpoint for actuators, lasers or any physical devices.I've seen an AWG being used as a remote controller for an RF toy. The freqency was low/high enough to do that.It's a quite versatile tool really.

author: ArchieAltz
author_rank: Contributor
timestamp: January 06, 2025, 05:21:13 pm
content: Quote from: tszaboo on January 06, 2025, 05:10:45 pmWhat should I look for when buying/making one ?

author: jwet
author_rank: Frequent Contributor
timestamp: January 06, 2025, 06:01:44 pm
content: Quote "What should I look for when buying/making one ?"Unfortunately, like all answers in engineering, it depends on the problems at hand.I'd say for an early beginner, I'd get a kit based on the XR2206 or the ICL8038. These can be bought on Amazon for $10. (Brand: Weewooday is one). They're likely cheaper on Ali Express etc. Most have three knobs on a box the size of a pack of cigarettes. These put out 1 Hz to 1 MHz in sine square and triangle, the amplitude and frequency can be adjusted. The specs are those of the Exar XR2206 chip used followed by an output amp- linearity and distortion are about 1%. Rise and Fall times less than 50 nS. The output impedance is 600 ohms. These are limitations but won't get in the way of you learning. Building this and playing with it will teach you a lot. Your investment won't be wasted as you progress, you will still find uses for it in the future.If you're truly impoverished and don't have the facilities to build a kit, I might suggest a PC based test equipment simulator, these use your sound card to make instruments generally in the audio range. VA32 is a good one that is a complete audio lab and would be good to have to look at the FG above if you build it. If not, there is one built. Another app is Waveforms by Digilent, this is designed to work with their fancy instruments but has a demo sound card mode that is pretty amazing.Good Luck.Build it carefully and play.

author: ArchieAltz
author_rank: Contributor
timestamp: January 06, 2025, 06:16:15 pm
content: Quote from: jwet on January 06, 2025, 06:01:44 pmwhat about ad9833 based kits ?

author: Gyro
author_rank: Super Contributor
timestamp: January 06, 2025, 06:30:47 pm
content: I sometimes wonder how many people buy modern function generators / AWGs to have something to look at on their scopes (including heartbeat waveforms and hearts). Either that or to complete their cosmetically matched Siglent / Rigol Scope, PSU and Function generator 'sets'.Pleasingly you mention building your own, which opens up the possibility of making more targeted instruments...If you're into audio then you probably want to build alow distortion(not the forte of most function generators) sine wave signal source, and bipolar square wave generator. Ideally the square wave should have decent speed edges for rise time measurements - a dedicated sub-ns pulse generator may be more appropriate for evaluating test equipment and, with decent construction, is simple to build.For logic use, a logic based pulse generator is probably more useful, providing variable (complimentary clock sources, variable width pulses and pulse streams.After considering the above, if you can't see a good match between what an off the shelf function generator provides and what you need, you shouldn't waste your money on one.

author: tszaboo
author_rank: Super Contributor
timestamp: January 06, 2025, 06:45:33 pm
content: Quote from: ArchieAltz on January 06, 2025, 05:21:13 pmUser interface, and usability. That's more important than specifications.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 06, 2025, 08:08:09 pm
content: Can be used to- to debug/repair/test a circuit- learn electronics, like in the video above, inject a signal then look at the outcome with an oscilloscope- improvise instruments that you need only rarely, and you don't have/or don't want to buy only for some occasional measurement. For example here I've used an AWG (Arbitrary Waveform Generator) + DSO (Digital Storage Oscilloscope) to measure the contact resistance between a banana connector and its binding terminal:https://www.eevblog.com/forum/projects/oscilloscope-with-trace-averaging-as-a-lock-in-amplifier-(rigol-ds1054z)/- automated testing, where you write a small sequence of SCPI commands to tell the instrument what to do, then save the results on a PC to view or post=process them later (very usefull when you need to make repetitive measurements), for example here, where the power was measured hundreds of times for each diode:https://www.eevblog.com/forum/rf-microwave/(unfolds)-00-diodes-square-law-region/- some other time I use the AWG as a +/-DC adjustable voltage- once I've calibrated the frequency of a quartz receiver, things like theseFor which one to buy, or if you need one, it depends on what kind of electronic you usually do. And most of all, how much do you want to spend. Can be a simple module of a few bucks from ebay, or can be a DIY build, or can be a more elaborated AWG of $100-1000 or more.

author: Old Printer
author_rank: Frequent Contributor
timestamp: January 06, 2025, 09:58:13 pm
content: If you really don't have much more than a curiosity at this point, one like this did me well for a while. I know this company does not sell it anymore, but they are all over ebay and AliExpress etc for cheap. A sound card on an old computer can be setup as one too.https://www.sainsmart.com/products/0-50khz-dds-function-signal-generator-module-custom-arbitrary-waveform?srsltid=AfmBOopuj6NSu0TwkiYevgMoYqsjDurKJ_LXhLdXzmKrQgb85TxICXKf

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: January 06, 2025, 10:24:42 pm
content: Perhaps consider the frequency range you will be working in. Most Function Generators are relatively low freq. Most of us who have function generators also have freq generators that have much higher freq output....100s of MHzYou may use a freq generator more at this point, I do not know...anyway perhaps think about what freq you would be using

author: ArchieAltz
author_rank: Contributor
timestamp: January 06, 2025, 10:52:28 pm
content: Quote from: RoGeorge on January 06, 2025, 08:08:09 pmI'm specifying in general electronics , so basically anything that runs on electrical energy . I believe that a simple kit or maybe even a diy circuit that can output around 12 MHz is the sweetspot for me.Still open to taking advice about which kit is the right for me (or a circuit design online which I can practicaly recreate).Thanks anyways :-)

author: wilfred
author_rank: Super Contributor
timestamp: January 06, 2025, 11:10:04 pm
content: Quote from: ArchieAltz on January 06, 2025, 02:50:41 pmProbably Software Defined Radio. Replacing all the analog hardware that does signal processing with software running on a CPU. These days digital means are used where once only analogue circuits were use to generate waveforms.

author: brucehoult
author_rank: Super Contributor
timestamp: January 07, 2025, 02:34:31 am
content: Quote from: wilfred on January 06, 2025, 11:10:04 pmRight. Effectively an RF function generator with arbitrary modulation (function) imposed on it.

author: Poroit
author_rank: Frequent Contributor
timestamp: January 07, 2025, 05:04:31 am
content: G'day ArchieAltz,Function generators are ideal for bench testing and Field testing Signal Transmitters/Converters that are used in Process Control.eg. Proximity Sensors, Flow sensors etc.https://www.apcs.net.au/products/frt150.html

author: RoGeorge
author_rank: Super Contributor
timestamp: January 07, 2025, 08:13:14 am
content: When you say 12MHz, why 12? What use do you have in mind where the limit of 12MHz would be enough?Yow didn't say how much do you plan to spend. Here's two brands of low cost yet professional instruments, to see what price level to expect:https://siglentna.com/waveform-generators/https://www.rigolna.com/products/waveform-generators/Can't say which one worth buying the most, I didn't look at the nowadays generators specs and features since 10 years ago, when I've bought my Rigol DG4102 AWG.From the specs that are a must have, would be (for me, others may want different):- two independent channels, one is not enough- aside from signal-output connector, must have a sync-output for each channel- good frequency stability, low phase-noise

author: ahsrabrifat
author_rank: Regular Contributor
timestamp: January 07, 2025, 08:17:50 am
content: Function generators are used in electronics labs. You can generate different types of waveforms with it. For example sine waves, square waves, sawtooth, triangular waves etc. This is basically a lab equipment.

author: NE666
author_rank: Frequent Contributor
timestamp: January 07, 2025, 10:15:38 am
content: Quote from: ArchieAltz on January 06, 2025, 05:08:44 pmAnd there's your 'problem'. You don't need it. That's evident from the fact you're asking what you'd use it for.So my advice would be to wait until such point in your education and experience as it becomes evident to you that you require that functionality, to solve a particular problem. At that point, you'll also know exactly what functional requirements you need it to satisfy. Outside of that, only purchase the cheapest, most basic unit you can find. That will satisfy some of your curiosity, whilst leaving you behind budget for a 'real' generator, once you know what 'real' is for your use-cases.

author: Aldo22
author_rank: Super Contributor
timestamp: January 07, 2025, 11:10:01 am
content: I have the cheapest “proper” arbitrary waveform generator available, theFY3224s.By “proper” I mean: 2 channel, max. 20Vpp, phase, offset, pulse, sweep, TTL output etc. and (USB) remote controllable so you can script it (Bode plot etc...).Other than that, it's not brilliant at anything, but it does the job for hobbyists.But nowadays almost every gadget has a signal generator built in.It just depends on what you need.Even the AN8008 DMM can generate a few square wave signals at different frequencies.Let me think about which of my “toys” generate signals.Fnirsi SG-003a process calibrator. Advantage: Can generate higher positive voltages (0-24V up to 200kHz).XR2206 kit: Advantage: No “stairs” like the AWG, otherwise not great.Hantek DSO2000 has an AWG built in. Advantage: Fast rise timeTinySA: Advantage: Sine waves up to 350MHz / NanoVNA for square waves.Fnirsi DSO-TC2: Up to 10MHz square.Zeeweii dso2512g: Various waveforms, sine up to 10MHz, fixed amplitude.Si5351 Arduino module: Square wave up to 160Hhz.Etc....Somehow they are everywhere, the only question is what you need in which situation.There are also some for Android, e.g.https://play.google.com/store/apps/details?id=com.keuwl.functiongeneratorPC sound card...

author: ArchieAltz
author_rank: Contributor
timestamp: January 07, 2025, 01:12:28 pm
content: Quote from: NE666 on January 07, 2025, 10:15:38 amYes , this is exactly what I was thinking about doing tbh , getting a cheap module or making one myself that can produce something in the 1-10 or 12mhz range just to be satisfied and to learn what I can use it for .

author: NE666
author_rank: Frequent Contributor
timestamp: January 07, 2025, 03:53:39 pm
content: Quote from: ArchieAltz on January 07, 2025, 01:12:28 pmI think that would be a great start, either using a known-good design with discrete components, or using an off-the shelf generator IC. Don't get too hung-up on the higher frequency range (maybe settle for up to 1Mhz, to start with), as all kinds of interesting effects start to creep in with prototyping/breadboarding construction methods.

author: ArchieAltz
author_rank: Contributor
timestamp: January 07, 2025, 07:20:39 pm
content: Quote from: NE666 on January 07, 2025, 03:53:39 pmThanks for the help man :-)

author: calzap
author_rank: Frequent Contributor
timestamp: January 07, 2025, 07:56:13 pm
content: If you have a scope, you should have a function generator. It can be useful for adjusting and testing the scope. And will have educational value used in conjunction with the scope. And there are myriad projects for which it is useful. As a beginner, start with a cheap generator … one that can do a few 10s of MHz and has sine and square waves. If you can get some modulation modes (AM, FM, pulse, etc.) without much extra cost, go for it. These are abundant on Amazon and eBay. Unless you really want to roll you own, I’d get one premade.Later, when you have more experience, get a higher spec generator if you have the need or desire. Higher end generators with GHz or 100s of MHz output and multiple waveforms and modulation modes are usually called signal generators.Mike

author: ArchieAltz
author_rank: Contributor
timestamp: January 07, 2025, 08:01:13 pm
content: Yeah I mean I got a solid enough DSO from UNI-T so I thought getting a function generator along with it

author: rstofer
author_rank: Super Contributor
timestamp: January 08, 2025, 01:21:39 am
content: Were I a student, I would be looking at the Digilent Analog Discovery 3 for all my instrumentation needs:https://digilent.com/shop/analog-discovery-3- check out the Features tabYes, it is expensive but compared to tuition and books it is pretty reasonable. I like the idea of carrying a laptop and an AD3 to the local coffeeshop (or wherever) to do my lab experiments. These things sold like hotcakes during Covid and a number of universities are using them for their lab classes instead of more expensive conventional instruments.The Pro Bundle is probably the way to go and then add other modules as you move along.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: January 08, 2025, 03:10:42 am
content: I have a low cost generator (it's just a board I assembled), for example I happen to use it in audio repairs by following the signal along the tracks