Author Topic: do i really need a Signal Generator?  (Read 10697 times)

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Offline dmkmedia

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do i really need a Signal Generator?
« on: January 02, 2017, 03:27:01 pm »
i have set up most of my equipment now the only thing i do not have is a Signal Generator.

and my question is do i really need one? and if so will a cheap one do for me as i dont even know what one is for ( dont laugh)

i know they generate a signal but really is this an option i will find useful as i move along in my electronics journey

 

Offline LazyJack

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Re: do i really need a Signal Generator?
« Reply #1 on: January 02, 2017, 03:34:29 pm »
It depends. What do you want to do? If you are doing RF stuff, you'll need one. If you're doing Arduino programming, you don't.
Also, what else do you have? Do you have a function gen?
 

Offline tggzzz

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Re: do i really need a Signal Generator?
« Reply #2 on: January 02, 2017, 03:50:02 pm »
The answer to the headline question is, of course, "no". Simple.

If you don't know what you would use it for, you wouldn't use it and therefore you wouldn't need it.

Accumulate requirements and get things to meet the requirements. Don't accumulate equipment and then invent requirements to fit the equipment.

OTOH, if you have a requirement, use understanding, skill and imagination to find a way to satisfy the requirement with whatever is to hand.
There are lies, damned lies, statistics - and ADC/DAC specs.
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Offline NivagSwerdna

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Re: do i really need a Signal Generator?
« Reply #3 on: January 02, 2017, 04:01:20 pm »
and my question is do i really need one?
I bought myself one, a signlent arb generator, when I had some spare cash but I rarely use it. I survived for decades using a microcontroller to generate square waves and also a bit of DtoA synthesis to produce sine waves.  So you probably don't need one and when you do... you can buy one... starting cheap...
 

Offline slicendice

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Re: do i really need a Signal Generator?
« Reply #4 on: January 02, 2017, 04:04:10 pm »
The answer to the headline question is, of course, "no". Simple.

If you don't know what you would use it for, you wouldn't use it and therefore you wouldn't need it.

Accumulate requirements and get things to meet the requirements. Don't accumulate equipment and then invent requirements to fit the equipment.

OTOH, if you have a requirement, use understanding, skill and imagination to find a way to satisfy the requirement with whatever is to hand.

This is a really good answer! I totally agree!
 

Offline dmkmedia

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Re: do i really need a Signal Generator?
« Reply #5 on: January 02, 2017, 04:42:16 pm »
The answer to the headline question is, of course, "no". Simple.

If you don't know what you would use it for, you wouldn't use it and therefore you wouldn't need it.

Accumulate requirements and get things to meet the requirements. Don't accumulate equipment and then invent requirements to fit the equipment.

OTOH, if you have a requirement, use understanding, skill and imagination to find a way to satisfy the requirement with whatever is to hand.

This is a really good answer! I totally agree!

and i would also have said the same thing 12 months ago but i am learning fast what things do and dont do. i was just a web designer  that had a few arduinos and raspberry pi's but now i am moving away from those and expanding my knowlage more. i think i will just get a cheap one for now and see what happens

and if i never use it what have a wasted £10
 

Offline KD0CAC John

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Re: do i really need a Signal Generator?
« Reply #6 on: January 02, 2017, 04:46:45 pm »
You need to learn enough to learn what you do not know .
One way to do that is buy one of the minimal , lets say $7 - $20 generators , a kit may be best , so you have part of what may be needed with a general repair / learning bench .
Then you may learn you need something costing $100 or even $3,000 ++ BUT BUY THE CHEAP ONE 1ST ;)
I've been in a number of trades requiring expensive test gear , and found that often learned more / faster [ and having access to the high end test geared , usually in someone else's shop ] that with the new knowledge / experience , that I could do a lot more with minimal test gear .
Then once your in the repair environment , you'l find good deals on good gear , for me finding dead / damaged gear , costs less and then learning to repair just gets me farther down the road .   
 

Online rstofer

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Re: do i really need a Signal Generator?
« Reply #7 on: January 02, 2017, 05:13:22 pm »
I have a function generator as part of my Digilent Analog Discovery I (highly recommended, especially the II version) but I thought I would buy one of the $40 units just to see how it works out.

https://www.amazon.com/Function-Generator-DIY-Tech-FG085/dp/B00C5UO8U6/ref=sr_1_13

Clearly, there will be more limitations on such an FG versus, say, a Rigol DG4162 or even the competing Siglent (which I still might buy one day) but for my limited needs, the FG085 will probably be more than adequate.

Mostly OT, I highly recommend the Analog Discovery as an electronics bench in a small box.  Dual channel scope, dual output arbitrary signal generator, 16 channel digital IO/logic analyzer, dual power supply and a whole lot of gadgets.  It is worth downloading the Waveforms software just to see the Demo capability.

http://store.digilentinc.com/analog-discovery-2-100msps-usb-oscilloscope-logic-analyzer-and-variable-power-supply/
https://reference.digilentinc.com/reference/software/waveforms/waveforms-3/reference-manual?redirect=1
http://store.digilentinc.com/all-products/software/

 

Offline tggzzz

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Re: do i really need a Signal Generator?
« Reply #8 on: January 02, 2017, 05:54:47 pm »
i think i will just get a cheap one for now and see what happens and if i never use it what have a wasted £10

The real loss will be your time rather than money. A cheap learning experience is not a bad way to go - but not necessarily the best.

There are so many signal generators to choose from, e.g. sine, square, triangle, arbitrary waveforms, various voltage/impedance outputs, frequency ranges, accuracy/stability, etc. Personally I would:
  • sit down, read a decent sig gen datasheet (i.e. not something on ebay/amazon)
  • understand what each of the specifications mean
  • think why feature X is mentioned (e.g. offset voltage)
  • think why parameter Y is specified, and what its limits means in practice (e.g. amplitude linearity 1%)
  • decide a task for which you might use a generator
  • work out what specifications you would need for that task

At the end of that you will probably have a better understanding and appreciation of signal generators than you would have after playing around with one for a few hours.

FYI, no recommendation is implied, but a random example of a decent datasheet: http://uk.rs-online.com/web/p/function-generators-counters/5138510/
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Offline dmkmedia

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Re: do i really need a Signal Generator?
« Reply #9 on: January 02, 2017, 09:30:43 pm »
thanks for the feedback
i will take it all on board
 

Offline Adam60

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Re: do i really need a Signal Generator?
« Reply #10 on: January 02, 2017, 11:27:35 pm »
If you want to go ultracheap, you could turn your smartphone into a very effective signal generator for probably less than $15-20. It will have limitations of course but every piece of equipmemt does.
 

Offline xani

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Re: do i really need a Signal Generator?
« Reply #11 on: January 03, 2017, 12:25:30 am »
i have set up most of my equipment now the only thing i do not have is a Signal Generator.

and my question is do i really need one? and if so will a cheap one do for me as i dont even know what one is for ( dont laugh)

i know they generate a signal but really is this an option i will find useful as i move along in my electronics journey

Generally if you don't know, dont get it. But if during some testing you start to think "gee, I wish I'd have a way to generate sine/square/triangle/ramp of that parameters" more than few times then you might want to start thinking about one.

Broadly they can be divided to 4 categories

* old-type analog ones (up to few MHz) - rarely worth getting unless super cheap
* "vanilla" DDS ones - usually its few to few tens of MHz + standard set of waves. sometimes some modulation options
* arbitrary waveform generators - as name implies, wider set of waves +  ability to program your own
* RF generators - no clue about them, never even touched one

You can go "cheap chinese" route and get something alike of https://www.aliexpress.com/item/Mini-Digital-Signal-Generator-DDS-Function-Signal-Source-Generator-Dual-channel-Arbitrary-Waveform-Frequency-Meter200MSa-s/32642068081.html and it probably do everything you need.

But honestly if you have to ask, you probably don't need it.
 

Offline lordvader88

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Re: do i really need a Signal Generator?
« Reply #12 on: January 03, 2017, 04:32:41 am »
I bought a DIY kit for under $10 for the fun of soldering it together and just to have 1. I can't remember its top frequency, but its into the kiloHertz, maybe 50kHz or 100kHz.

I plan on using it fooling around with old radios.
 

Offline KD0CAC John

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Re: do i really need a Signal Generator?
« Reply #13 on: January 03, 2017, 01:15:09 pm »
When thinking / working with signal generators , you have to remember that there a lot of differences again , like audio frequencies and RF - radio frequencies , generally different equipment .
There frequency generator apps for smart phones , but they audio .
Just need to match the work & the signal .
 

Offline 4cx10000

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Re: do i really need a Signal Generator?
« Reply #14 on: January 03, 2017, 02:06:01 pm »
Well, to be honest ... you will most probably see that a signal generator will come in handy before you know it. I would, in your case, buy something cheap to play with and at a later stage of your hobby career - might as well be professional - you will find out what to choose. Since you probably do not know were you are headed and as the budget at times is a big obstacle, just let it rest until you go further with needs that may put nearly total emptiness in your wallet. I am sure that you sooner or later will find out... :)
 

Offline slicendice

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Re: do i really need a Signal Generator?
« Reply #15 on: January 03, 2017, 02:22:47 pm »
Personally I never buy anything if I don't need it. If I'd go and by everything I think I need I would end up having a second apartment full of junk that I though I need. Same goes for the signal generator, if I don't know what I would use it for, I won't buy it. And it's not that I will miss any business opportunity because I don't have a signal gen ready when needed, because there's no point in running a full business until one is educated enough to know exactly in what situations such device would come in handy. So I can wait for the thing to get shipped, once I have a clue where I need it and then I can experiment with it.

First thing I would buy is a soldering iron, variable power source and a multimeter(or 2). And even before buying the soldering iron I would get a breadboard and a bunch of components to experiment with. :-)
 

Offline 4cx10000

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Re: do i really need a Signal Generator?
« Reply #16 on: January 03, 2017, 02:51:00 pm »
Quote
If I'd go and by everything I think I need I would end up having a second apartment full of junk that I though I need.
That could be me with three barns full of electronic stuff!  ;D Just kidding!! Remember that OT is on his first step and why not invest in what could be a useful tool? A small signal generator is easily hidden in a drawer or bookshelf if the needs is not as expected. If it is all about the money, yes! But a cheap generator would probably not cause a serious impact on your economy. It is all about the money? Right? Besides, it is just a gorgeous little thing that can do things that will play the most beautiful screen shoots on a scope, well that is if you get bored once in a while  ;D
« Last Edit: January 03, 2017, 02:57:54 pm by 4cx10000 »
 

Online rstofer

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Re: do i really need a Signal Generator?
« Reply #17 on: January 06, 2017, 02:49:35 am »
I have a function generator as part of my Digilent Analog Discovery I (highly recommended, especially the II version) but I thought I would buy one of the $40 units just to see how it works out.

https://www.amazon.com/Function-Generator-DIY-Tech-FG085/dp/B00C5UO8U6/ref=sr_1_13


This FG085 Function Generator is a pretty neat little gadget.  It generates a number of waveforms (Sine, Square, Ramp, Staircase, Triangle, Servo, User) over a fairly modest frequency range.  It seems to me like the frequencies will go a bit higher than the manual says but, in general, the Sine function can run up to 200 kHz, all the others are limited to 10 kHz.  That's fairly low but many bench applications can use this quite well.

It's worth reading through the User Manual if this unit is considered:

http://www.jyetech.com/Products/085/Manual_085F.pdf

It certainly won't replace a full Arbitrary Waveform Generator but it's a pretty slick for $40.  You can even build up a 256 entry arbitrary waveform.

« Last Edit: January 06, 2017, 05:33:44 pm by rstofer »
 

Offline slicendice

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Re: do i really need a Signal Generator?
« Reply #18 on: January 06, 2017, 08:54:03 am »
If you are at the point that you want to make audio related stuff, then a signal generator will become very useful. But you also need a really good scope for that. If you can afford a proper scope, then a signal generator should not be an issue. Many scopes even got some basic signal generators built in, which could be useful but not necessary as external generators usually have more properties.
 

Online tooki

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Re: do i really need a Signal Generator?
« Reply #19 on: January 07, 2017, 12:20:53 am »
i have set up most of my equipment now the only thing i do not have is a Signal Generator.

and my question is do i really need one? and if so will a cheap one do for me as i dont even know what one is for ( dont laugh)

i know they generate a signal but really is this an option i will find useful as i move along in my electronics journey
My take, as an electronics novice (did a bit as a kid, been rediscovering it for the past 2 years): When you need a function generator, you'll know. Don't bother getting one before that.

For me, it was when beginning to work with analog circuits like opamps. At the moment I use a signal gen app on my iPhone to make sine waves (of course, limited to about 20KHz) and an arduino to make basic square waves. In some experiments, I've wanted signals those two sources couldn't generate, so I think my next acquisition will be a function gen. I'm thinking I'll start with a cheap kit off fleabay, so that I also have the fun of assembly.
 

Online rstofer

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Re: do i really need a Signal Generator?
« Reply #20 on: January 07, 2017, 02:06:15 am »
So much depends on what kind of electronics you want to play with.  A simple example:  How about a low pass RC filter?  Want to verify the corner frequency?  Want to really understand fc = 1/(2*PI*R*C)?

Breadboard the circuit and use a DMM to measure the input and output voltage.  The corner frequency occurs where the output voltage is .707 times the input voltage (70.7%).  The DMM is easy but how to get a varying input sine wave?  With a signal generator...

As I said, it depends on what you want to do.  My interest lie primarily in the digital domain and I don't spend a lot of time with sine waves.  Still I have a couple of signal generators (nothing fancy) just in case I want to demonstrate something to my grandson.
 

Online xrunner

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Re: do i really need a Signal Generator?
« Reply #21 on: January 07, 2017, 02:22:17 am »
When you need a function generator, you'll know. Don't bother getting one before that.

Yep.

If you have no requirement to generate signals, i.e. sine waves, square waves, or other stimulus for circuits or testing - then you don't need one. I have one to help me with ham equipment repair. For example, I can use a low frequency sine generator to modulate my RF generator to make an FM signal with a tone encoded transmission to test FM receivers with tone squelch. That's just one example. Or to test the audio response of an audio amplifier you can sweep a sine wave from F1 to F2 and observe the output response.

If you want one to play with, then by all means get a cheap one  :-/O, and play with it. But as I said, if you have no need for it, then you just do not have to have one.
I am a Test Equipment Addict (TEA) - by virtue of this forum signature, I have now faced my addiction
 

Offline Zx Spectrum

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Re: do i really need a Signal Generator?
« Reply #22 on: January 07, 2018, 04:06:34 am »
So much depends on what kind of electronics you want to play with.  A simple example:  How about a low pass RC filter?  Want to verify the corner frequency?  Want to really understand fc = 1/(2*PI*R*C)?

Breadboard the circuit and use a DMM to measure the input and output voltage.  The corner frequency occurs where the output voltage is .707 times the input voltage (70.7%).  The DMM is easy but how to get a varying input sine wave?  With a signal generator...

As I said, it depends on what you want to do.  My interest lie primarily in the digital domain and I don't spend a lot of time with sine waves.  Still I have a couple of signal generators (nothing fancy) just in case I want to demonstrate something to my grandson.

actually my interest and eventual target is in digital application too.
but i want to buy function gen to learn some basic AC stuff. do you think i would ever need a dual channel one. as i said i will never work in audio nor RF stuff.
 

Offline David Hess

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Re: do i really need a Signal Generator?
« Reply #23 on: January 07, 2018, 02:39:07 pm »
If you have an oscilloscope then you should have a function generator.  Combining the two allows manual low frequency vector network measurements, transient response measurements, and curve tracing.  Even without an oscilloscope, a function or audio signal generator is useful with an AC voltmeter to do things like tune speaker enclosures.
 

Offline tggzzz

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Re: do i really need a Signal Generator?
« Reply #24 on: January 07, 2018, 05:25:57 pm »
If you have an oscilloscope then you should have a function generator.  Combining the two allows manual low frequency vector network measurements, transient response measurements, and curve tracing.  Even without an oscilloscope, a function or audio signal generator is useful with an AC voltmeter to do things like tune speaker enclosures.

Yes, but often you simply create a signal source specifically for the current project, often as part of the project.

It can be argued that if the primary interest is digital, then a pattern generator might be more useful.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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