How to use? a function generator  - Page 1
Forum section: electronics / beginners

author: dalpets
author_rank: Contributor
timestamp: February 26, 2024, 05:08:09 pm
content: I have used a ? mark in the title here because my many attempts to ascertain detailed info on function generator usage has not met with success. I use the word 'usage' as a vague generalization only because my present knowledge can only assume that it is no more than an instrument to be used as a template for the diagnosis of DUTs, in conjunction with an oscilloscope. Another description could be 'configuration' but nothing I have seen anywhere provides helpful explanations.My best explanation of the problem I have is how its setup needs to be specifically tailored for a multitude of possible types of DUTS, not only in terms of waveforms, but also other setting that would affect diagnostic accuracy.Thanks for your help.

author: CaptDon
author_rank: Super Contributor
timestamp: February 26, 2024, 05:23:14 pm
content: Your device under test determines the requirement. Do you need a sinewave for audio testing, do you need a TTL level wave for logic testing, do you need a somewhat higher voltage squarewave or single pulse for CMOS logic testing. No one here can say Set the offset for XXXX, set the amplitude for XXXX, YOU are the one who will determine what waveshape and voltage your testing will require, not us. Your question is far to vague to be answered intelligently. I would guess if you have a need for a function generator you would also know how and when to use it and what to use it for?

author: pqass
author_rank: Super Contributor
timestamp: February 26, 2024, 05:59:20 pm
content: What you're trying to test for drives the setup of the FG; not the other way around.If I was testing a power amplifier to determine max. power output, I'd setup the FG for 1kHz sine, 10mVpp output initially, and 0V offset. My 'scope and MM (on ACV) would be monitoring the speaker terminals and I'd ramp up the output to a max. of 900mVpp (line level) as I check the waveform for any signs of clipping. Take note of the ACV reading (at just under clipping) to determine power (P=VAC^2/4ohm load).My 'scope can do Bode plots automatically. Its built-in FG will ramp up the frequency from 10Hz to 20kHz, plotting amplitude and phase and give a nice graph. Of course this was once (and still can be) done manually with pen and paper. You decide, levels, frequency range, number of points, etc.A typical FG can output 10Vpp, sine/square/triangle/ramp, +/-5V offset, 10Hz to 15MHz frequency and has a 50ohm output impedance. If your test need is beyond this, then you'll have to pick another signal source or, if you can, adapt the output to your need.

author: dalpets
author_rank: Contributor
timestamp: February 26, 2024, 06:36:13 pm
content: Quote from: CaptDon on February 26, 2024, 05:23:14 pmNot necessarily. I'm a complete beginner!I'm trying to learn & I have to start somewhere. Thus I need to ask questions, as purile as they may seem to a seasoned user.

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: February 26, 2024, 07:42:43 pm
content: Before rushing to make something on a breadboard, buying an oscilloscope, function generator, etc. you might consider circuit simulator software.The easier one to use, as it has “instruments” you add to the circuit diagram, is Tina. It isn’t free, but does include power, function generator, oscilloscope and signal analyser in the lowest cost student version (49 Euros). Note Tina is more oriented towards education and training than the free LTSPICE. I have both Tina and LTSpice, for most things I use Tina as I am more familiar with it.If your interest is more logic based, the old fashioned logic probe is a basic way to check logic 0 and 1 with red or green LED indicators, or if you are showing off, a 7 segment display to show 0, 1, or the decimal point for pulses (made one myself in the 1970s).A breadboard can be educational, but it can be frustrating if you can’t get something to work. With the simulator, you can share the circuit and quickly obtain feedback.Did you have any particular type of circuit/project in mind for your function generator?https://www.tina.com/SJ

author: MathWizard
author_rank: Super Contributor
timestamp: February 27, 2024, 03:39:12 am
content: There's a few circuit simulators way easier to use than LTSpice level programs. I don;t know any to recommend, years ago I think I used CircuitMaker freeware or some pirate version.There's online web-browser ones too. Some of the program ones will make an animated circuit, so you can see current flowing, some probably show voltages too, with colors or whatever.

author: pqass
author_rank: Super Contributor
timestamp: February 27, 2024, 04:59:27 am
content: I usefalstadfor a quick+dirty on-line circuit simulator to verify snippets before breadboarding/prototyping and sharing ideas with others on this forum.

author: Muxr
author_rank: Super Contributor
timestamp: February 27, 2024, 05:27:23 am
content: A signal generator is a pretty versatile piece of equipment. You can use it for all sorts of things.Say you want to test a full bridge rectifier component and to see how it behaves? You can use a signal generator to provide the AC input and then investigate the circuit with your multimeter or a scope.You could be building a low pass filter, which is supposed to attenuate higher frequencies. Well you can use the signal generator and a scope to test the behavior and attenuation of the said filter at different frequencies.And these examples just scratch the surface of possible uses.Basically a signal generator allows you to "simulate" different input signals and see how your DUT behaves given those signals.

author: Ian.M
author_rank: Super Contributor
timestamp: February 27, 2024, 08:01:56 am
content: Beware: Many function/signal generators have a ground referenced output so are unsuitable for testing a bridge rectifier with its output connected to an ordinary scope with ground referenced inputs.See:https://www.eevblog.com/forum/beginners/full-wave-bridge-rectifier-only-half-rectifying/

author: BillyO
author_rank: Super Contributor
timestamp: February 28, 2024, 02:57:16 am
content: Quote from: Ian.M on February 27, 2024, 08:01:56 amMost generators that are not in the "toy" category are ground referenced.To the OP:There are a limited number of basic parameters that all decent function generators offer.WaveformFrequencyAmplitudeOffsetOf course modern DDS generators of higher coast can do a lot more than this, but if you are a rank beginner trying to explain things like sweep, modulation and inter-channel phase will be impossible unless you first understand and are familiar with the 4 basics. I would suggest you concentrate on those and direct your questions as to how they should be configured for specific purposes rather than ask "What can a function generator do for me?".Better still, get yourself a cheap used analog function generator and use it. It will be about a million times easier to assimilate than some $3000 multi-channel modern DDS generator with 50 parameters to mess with. It's usually better to learn to walk before running a 100 meter sprint.Just my take on it.

author: Aldo22
author_rank: Super Contributor
timestamp: February 28, 2024, 10:43:11 am
content: I don't think he wants to buy a function generator.In another thread he says:Quotehttps://www.eevblog.com/forum/beginners/function-generatoroscilloscope-synergies/msg5329562/#msg5329562I think the topic starter just doesn't know what to do with it or how to use it sensibly.But I don't really understand his question.

author: armandine2
author_rank: Frequent Contributor
timestamp: February 28, 2024, 01:06:05 pm
content: Quote from: dalpets on February 26, 2024, 05:08:09 pmThe devil is in the detailas they say - by the sounds of it I'm in much same boat [not an uncommon experience].My default learning is often from a specific text or a something seen in a YouTube video. Getting decent material is not so easy but I think it is out there.

author: themadhippy
author_rank: Super Contributor
timestamp: February 28, 2024, 02:46:29 pm
content: Quotewoa how did i ever learn anything ,scopes and signal generators were a distant dream requiring many decades worth of pocket money saving,and the internet hadn't been born. Only resources we had were magazines and a thing called books ,borrowed from a place called a library,but you had to get an adult to borrow them for you as they required an adult ticket.

author: BillyO
author_rank: Super Contributor
timestamp: February 28, 2024, 03:19:13 pm
content: Quote from: Aldo22 on February 28, 2024, 10:43:11 amI don't think anyone understands his question, not even the OP.So my advice would be much the same. Hook the FG to the scope and play around with the 4 basic parameters of waveform, frequency, amplitude and offset until he is familiar with them. This would give him some practice with both instruments. Then he can move on to putting various devices between them, like simple filters and such. After that move on to some transistor amplifiers or op-amps and so forth.A book on using test equipment might also be a boon.

author: rstofer
author_rank: Super Contributor
timestamp: February 28, 2024, 04:47:03 pm
content: The easy way to generate digital signals is with a uC. It can be a simple uC like am Arduino or as complex as a Teensy 4.1.For analog signals, an arbitrary waveform generator can create very complex signals by combining base frequencies along with their harmonics, possibly phase shifted, at various amplitudes. We were playing with a heart shaped waveform for Valentines Day a few years back (2017).https://www.eevblog.com/forum/chat/a-valentine_s-day-activity-for-your-scope-and-function-generator/msg1136847/#msg1136847See the scope display at Reply 4