Most accurate signal generator

[bdunham7]

The prize for actual "most accurate signal generator" probably goes to one of the JAWS (Josephson Arbitrary Waveform Synthesizer) developed by several national metrology institutes.

Note that even the $550,000 JAWS 2V system would not quite meet the OP's initial accuracy requirement of 1 part in 100,000 over the audio range.    

see the top of p. 3

https://www.nist.gov/system/files/documents/2023/01/10/6011.pdf

[DaneLaw]

The prize for actual "most accurate signal generator" probably goes to one of the JAWS (Josephson Arbitrary Waveform Synthesizer) developed by several national metrology institutes.

Note that even the $550,000 JAWS 2V system would not quite meet the OP's initial accuracy requirement of 1 part in 100,000 over the audio range.    

see the top of p. 3

https://www.nist.gov/system/files/documents/2023/01/10/6011.pdf

Then what would?
Let's help OP get his "most accurate signal generator" that matches his criteria.
A custom jobby build to tolerances by a big brand name, so OP can exchange his TC3 Fnirsi and his 15 USD FG-100 for one of those..
Accuracy matters..!

[loop123]

I think SDG6022X signal accuracy should be good enough for amateur needs.
https://siglentna.com/product/sdg6022x/

But its performance is not the best. So, if you want better performance, there is may be a sense to look for some specialized signal generator for your needs?

What do you mean when talking "most accurate"? Less noise / less spurs / high dynamic range? 

If you're interested in precise amplitude, then there is a sense to look for RF generator. They have pretty clean sine output and allows to setup calibrated amplitude. But note, all signal generators have fixed output impedance, usually 50 Ω (sometimes there is a switch between 50 Ω and 600 Ω). And if your load is not 50 Ω, then you're needs to recalculate amplitude, that is normal and expected behavior.

The use is specifically to test the E1DC Cosmos ADC to see if for example it's 0dB corresponds to 1.7V or 1.8V in its lowest setting (with best dynamic range). Just to test its overall accuracy. My present 2 signal generators don't even produce output where I can be certain it's 1V or 1.5V for example. So I need one where I can produce accurate 1.7V or 1.8V to see which voltage would clip it and establish the baseline because different units vary according to the manufacturer. I didn't know choosing signal generator is that complicated that is why didn't post the entire picture below in the original message. In the following is the -128dB noise floor of my E1DA I tested using REW RTA. My budget for the stand alone signal generator is less than $200. Please recommend which one specifically I should get knowing my requirements. Thanks.

https://e1dashz.wixsite.com/index/cosmos-adc

[bdunham7]

I didn't know choosing signal generator is that complicated that is why didn't post the entire picture below in the original message. In the following is the -128dB noise floor of my E1DA I tested using REW RTA. My budget for the stand alone signal generator is less than $200. Please recommend which one specifically I should get knowing my requirements. Thanks.

The models I mentioned would more than suffice but they blow your budget.  The cheap and cheerful FY6900 will mostly likely work just fine, but I couldn't personally guarantee it without testing the unit first.

https://www.aliexpress.us/item/3256802190692386.html

[nctnico]

I didn't know choosing signal generator is that complicated that is why didn't post the entire picture below in the original message. In the following is the -128dB noise floor of my E1DA I tested using REW RTA. My budget for the stand alone signal generator is less than $200. Please recommend which one specifically I should get knowing my requirements. Thanks.

The models I mentioned would more than suffice but they blow your budget.  The cheap and cheerful FY6900 will mostly likely work just fine, but I couldn't personally guarantee it without testing the unit first.

https://www.aliexpress.us/item/3256802190692386.html

The UNI-T UTG932E will also work and is generally available from local distributors which helps with warranty issues (or returning it if it turns out to be no good). I have no hands-on experience with the UNI-T UTG932E or the FY6900, but the UTG932E looks like it has a better user interface as well.

But either will be way better compared to the FG-100 according to this review: https://hackaday.com/2018/05/17/review-fg-100-dds-function-generator/ Spoiler alert: the FG-100 is a waste of money.

[Fungus]

The UNI-T UTG932E will also work and is generally available from local distributors which helps with warranty issues (or returning it if it turns out to be no good).

I got mine on Amazon.

I have no hands-on experience with the UNI-T UTG932E

It works well enough. A lot of EEVBLOG owners have one.

[loop123]

i only need sine wave at 1.8V. Arent there cheap modules where it just produces constant 1.8V sine wave? How to build one if none offered. Also why is it hard to make accurate sine wave generators. Dont you just need a crystal for clock. Is it not a crystal is very accurate like used in processor. Its not like you have to synchronize it with the frequency of pulsar star. Are you saying crystals used in clocks in processor or adc are dirty or not pure so the output from mechanical oscillators are not unform??

[Fungus]

i only need sine wave at 1.8V. Arent there cheap modules where it just produces constant 1.8V sine wave? How to build one if none offered.

Get something with more than 1.8V, put a potentiometer across the output so you can dial a voltage, and look at it on an oscilloscope?

[Bud]

Also why is it hard to make accurate sine wave generators. Dont you just need a crystal for clock. Is it not a crystal is very accurate like used in processor.

Processors do not give shit about clock accuracy.

Its not like you have to synchronize it with the frequency of pulsar star.

With your requirements it seems this is what you have to do, i.e. use a GPS disciplinned oscillator, or a rubidium oscillator. Do your research how to build them or how much a commercially built one may cost.

  Are you saying crystals used in clocks in processor or adc are dirty or not pure so the output from mechanical oscillators are not unform??

Crystals have large (compare to your requirements) temperature, tolerance and aging drift. To satisfy your requirements you need a different frequency reference 1000 times better. Crystals will change frequency when you look wrong at them.

[loop123]

Also why is it hard to make accurate sine wave generators. Dont you just need a crystal for clock. Is it not a crystal is very accurate like used in processor.

Processors do not give shit about clock accuracy.

Its not like you have to synchronize it with the frequency of pulsar star.

With your requirements it seems this is what you have to do, i.e. use a GPS disciplinned oscillator, or a rubidium oscillator. Do your research how to build them or how much a commercially built one may cost.

  Are you saying crystals used in clocks in processor or adc are dirty or not pure so the output from mechanical oscillators are not unform??

Crystals have large (compare to your requirements) temperature, tolerance and aging drift. To satisfy your requirements you need a different frequency reference 1000 times better. Crystals will change frequency when you look wrong at them.

You mean its difficult even to produce accurate 1.8V sine wave?  Is the voltage or sine wave more difficult to make or which one is more affected by a crystal/clock? usually what are the errors in crystal just to have an idea? but then if crystals vary how do wifi or cell phone even connect?

[Anthocyanina]

Also why is it hard to make accurate sine wave generators. Dont you just need a crystal for clock. Is it not a crystal is very accurate like used in processor.

Processors do not give shit about clock accuracy.

Its not like you have to synchronize it with the frequency of pulsar star.

With your requirements it seems this is what you have to do, i.e. use a GPS disciplinned oscillator, or a rubidium oscillator. Do your research how to build them or how much a commercially built one may cost.

  Are you saying crystals used in clocks in processor or adc are dirty or not pure so the output from mechanical oscillators are not unform??

Crystals have large (compare to your requirements) temperature, tolerance and aging drift. To satisfy your requirements you need a different frequency reference 1000 times better. Crystals will change frequency when you look wrong at them.

You mean its difficult even to produce accurate 1.8V sine wave?  Is the voltage or sine wave more difficult to make or which one is more affected by a crystal/clock? usually what are the errors in crystal just to have an idea? but then if crystals vary how do wifi or cell phone even connect?

making a sine wave is ridiculously easy, making a sine wave 1.8v in amplitude is easy, making a sine wave within the frequency range you need is also easy, but, making it precisely 1.8v to the 10uV of deviation you want, and within the 10uHz you want, that's where it approaches the physically impossible if not already there, and absolutely impossible for 200$, but also it is very unlikely that you (or most people) need a signal source with those specifications.

crystal frequency can vary depending on temperature, pressure on it because of minor PCB bends and how the materials bend differently due to temperature changes, other factors can also influence the frequency stability of the crystal, maybe minor defects in the crystal structure itself, in the manufacture process...

those radio systems can connect because they have a tolerance range that accounts for the physically, practically and economically realizable components and designs.

and about the voltage stability, a big reason why AM radio sounds so bad when compared to FM radio, noise is everywhere, and gets everywhere, and you see that in the form of variations in amplitude. if you capture a single period of a sine wave, it will not be perfectly sinusoidal, but you'll see it's a bit "frizzy", its amplitude at any x point deviating slightly from what you'd get from calculating sin(x)

[loop123]

You mean its difficult even to produce accurate 1.8V sine wave?  Is the voltage or sine wave more difficult to make or which one is more affected by a crystal/clock? usually what are the errors in crystal just to have an idea? but then if crystals vary how do wifi or cell phone even connect?

making a sine wave is ridiculously easy, making a sine wave 1.8v in amplitude is easy, making a sine wave within the frequency range you need is also easy, but, making it precisely 1.8v to the 10uV of deviation you want, and within the 10uHz you want, that's where it approaches the physically impossible if not already there, and absolutely impossible for 200$, but also it is very unlikely that you (or most people) need a signal source with those specifications.

crystal frequency can vary depending on temperature, pressure on it because of minor PCB bends and how the materials bend differently due to temperature changes, other factors can also influence the frequency stability of the crystal, maybe minor defects in the crystal structure itself, in the manufacture process...

those radio systems can connect because they have a tolerance range that accounts for the physically, practically and economically realizable components and designs.

and about the voltage stability, a big reason why AM radio sounds so bad when compared to FM radio, noise is everywhere, and gets everywhere, and you see that in the form of variations in amplitude. if you capture a single period of a sine wave, it will not be perfectly sinusoidal, but you'll see it's a bit "frizzy", its amplitude at any x point deviating slightly from what you'd get from calculating sin(x)

No. I just wrote 1.00001V to drive the point that it should not be 1.2V or 0.9V but exactly 1V. It doesn't have to be 1.00001V but only 1.01 volt for example. It is enough. With that clarified. I just need a sine wave generator that can produce 1.8V (error of 1.801V) and 5000Hz (not 5001Hz or 4999 Hz). How do you build them anyway? Since I'd rarely use it. My budget for finished product (I want ot avoid building it) is lower to $50..

[ebastler]

No. I just wrote 1.00001V to drive the point that it should not be 1.2V or 0.9V but exactly 1V. It doesn't have to be 1.00001V but only 1.01 volt for example. It is enough. With that clarified. I just need a sine wave generator that can produce 1.8V (error of 1.801V) and 5000Hz (not 5001Hz or 4999 Hz). How do you build them anyway? Since I'd rarely use it. My budget for finished product (I want ot avoid building it) is lower to $50..

You are still very unclear regarding the accuracy you need (or want). So what is the voltage error you allow -- 0.01 V or 0.001 V? And what is the frequency error you allow -- less than 1 Hz, but how much can you tolerate? 0.1 Hz?

And you are very unclear regarding the budget. If it is $50, why did you tell us $200 before?

[ebastler]

Here's an idea, if you are on a low budget: Keep your cheap generator, but buy a multimeter which lets you check its frequency and measure & adjust its output.

Most low-cost multimeters will not work for this, since their AC measurement capability is only specified up to 1 kHz or less. But e.g. the UNI-T UT61E is specified up to 10 kHz, hence should provide decent measurements for much of your desired audio range.

Its accuracy will be limited though; it's a bit better than 1% for AC voltage. [Edit: It's actually a tad worse than 1% when you go above 1 kHz.] Resolution will be much better. See the specifications for details.

[bingo600]

For "purity" i have an old HP 3324A
Large , and might be a bit over your budget.

DS
https://accusrc.com/uploads/datasheets/6876_3324a.pdf

Nice options
https://www.ebay.com/itm/364625638885?


https://www.ebay.com/itm/364545127053?

[Aldo22]

No. I just wrote 1.00001V to drive the point that it should not be 1.2V or 0.9V but exactly 1V. It doesn't have to be 1.00001V but only 1.01 volt for example. It is enough. With that clarified. I just need a sine wave generator that can produce 1.8V (error of 1.801V) and 5000Hz (not 5001Hz or 4999 Hz). How do you build them anyway? Since I'd rarely use it. My budget for finished product (I want ot avoid building it) is lower to $50..

You're starting to look like a troll to me.
First you have $200 now $50.
First you want 10uV error, then you want 10mV error and now 1mV?
Anyway, the only halfway complete (new) signal generator for $50 that I know of is the FY3200S.
It is what it is. Not nearly what you want, but obviously you don't really know. (Attached an excerpt of the specs for FY3200S)

P.S. At least FY3200S has detailed manufacturer specs, which isn't necessarily a given for $50. 

[BennoG]

The OP probably does not understand that the output load needs to be 50 ohm. If you not load the generator with 50 ohm the output voltage is usually double the output voltage you set on the generator.

Or for the el cheapo chinese the unloaded output is the set voltage and as soon as you put a load on the output the voltage drops.

Benno

[ebastler]

The OP probably does not understand that the output load needs to be 50 ohm. If you not load the generator with 50 ohm the output voltage is usually double the output voltage you set on the generator.

Or for the el cheapo chinese the unloaded output is the set voltage and as soon as you put a load on the output the voltage drops.

Good point, and another good reason to get a multimeter next (capable of AC measurements in the required frequency range). Flying blind is never a good idea...

Of course an oscilloscope would be an even better tool, but is probably outside the OP's budget at the moment if any level of amplitude accuracy is required.

[loop123]

No. I just wrote 1.00001V to drive the point that it should not be 1.2V or 0.9V but exactly 1V. It doesn't have to be 1.00001V but only 1.01 volt for example. It is enough. With that clarified. I just need a sine wave generator that can produce 1.8V (error of 1.801V) and 5000Hz (not 5001Hz or 4999 Hz). How do you build them anyway? Since I'd rarely use it. My budget for finished product (I want ot avoid building it) is lower to $50..

You're starting to look like a troll to me.
First you have $200 now $50.
First you want 10uV error, then you want 10mV error and now 1mV?
Anyway, the only halfway complete (new) signal generator for $50 that I know of is the FY3200S.
It is what it is. Not nearly what you want, but obviously you don't really know. (Attached an excerpt of the specs for FY3200S)

P.S. At least FY3200S has detailed manufacturer specs, which isn't necessarily a given for $50. 

The $200 you guys mentioned are so complex with dozens of functions like square waves and even custom waves. I dont need them I just need sine wave so I think I need single $50 accurate sine wave output only. well. I thought its easy to get 1.8000001V accuracy. But it would be too costly or impossible as you guys say. So I need it to be accurate to 1.80V only, that is good enough. Frequency should be like 3000.0Hz accurate.

[Antonio90]

No. I just wrote 1.00001V to drive the point that it should not be 1.2V or 0.9V but exactly 1V. It doesn't have to be 1.00001V but only 1.01 volt for example. It is enough. With that clarified. I just need a sine wave generator that can produce 1.8V (error of 1.801V) and 5000Hz (not 5001Hz or 4999 Hz). How do you build them anyway? Since I'd rarely use it. My budget for finished product (I want ot avoid building it) is lower to $50..

You're starting to look like a troll to me.
First you have $200 now $50.
First you want 10uV error, then you want 10mV error and now 1mV?
Anyway, the only halfway complete (new) signal generator for $50 that I know of is the FY3200S.
It is what it is. Not nearly what you want, but obviously you don't really know. (Attached an excerpt of the specs for FY3200S)

P.S. At least FY3200S has detailed manufacturer specs, which isn't necessarily a given for $50. 

The $200 you guys mentioned are so complex with dozens of functions like square waves and even custom waves. I dont need them I just need sine wave so I think I need single $50 accurate sine wave output only. well. I thought its easy to get 1.0800001V accuracy. But it would be too costly or impossible as you guys say. So I need it to be accurate to 1.80V only, that is good enough. Frequency should be like 3000.0Hz accurate.

It is hard, because the 0.0000001 part of the voltage specified is around 0.1 parts per million. The problem is that kind of accuracy is buried in the noise, and close to the physical limits.

It is not rare to have resistors, capacitors, traces on the PCB, etc, have a variation of  more than 10ppm/C, which means that a variation in temperature in your lab of a tenth of a degree would already throw off the accuracy of the voltage supplied, unless you spend thousands on precission components, temperature compensation, and ovenize the whole stuff.

Maybe you could pick a book on basic circuit analysis (Malvino has a very good one) and have a look at the first chapters, which would help you make more reasonable questions. If you write 1.800001V, it is assumed that all digits are significant which, for audio, they are not, and what you need is relative accuracy (in/out), and not absolute, which you implied.

Also, the signal generators on your first post should be able to specify the output voltage. Why do you say you cannot know it?

As per your requirements of a clean sine-wave source for $50 max, I'm not aware of any existing product. You can use your PC soundcard and an amplifier, or probably look on the second hand market. There are usually a lot of older waveform generators for around $50.

Also, if you expect to find a generator in which you set 1.5V and you get 1.5V connecting it to a random multimeter/audio amplifier/oscilloscope/whatever, you will be disappointed. Signal generators are generally specified for an output impedance of 50 Ohms, if you don't match the impedances, the volts out will not match what you set on the waveform generator's screen. Maybe look around a bit about impedance matching, it might even be the case that the FNIRSI on the first post is actually enough for your needs.

[nctnico]

No. I just wrote 1.00001V to drive the point that it should not be 1.2V or 0.9V but exactly 1V. It doesn't have to be 1.00001V but only 1.01 volt for example. It is enough. With that clarified. I just need a sine wave generator that can produce 1.8V (error of 1.801V) and 5000Hz (not 5001Hz or 4999 Hz). How do you build them anyway? Since I'd rarely use it. My budget for finished product (I want ot avoid building it) is lower to $50..

You're starting to look like a troll to me.
First you have $200 now $50.
First you want 10uV error, then you want 10mV error and now 1mV?
Anyway, the only halfway complete (new) signal generator for $50 that I know of is the FY3200S.
It is what it is. Not nearly what you want, but obviously you don't really know. (Attached an excerpt of the specs for FY3200S)

P.S. At least FY3200S has detailed manufacturer specs, which isn't necessarily a given for $50. 

The $200 you guys mentioned are so complex with dozens of functions like square waves and even custom waves. I dont need them I just need sine wave so I think I need single $50 accurate sine wave output only. well. I thought its easy to get 1.8000001V accuracy. But it would be too costly or impossible as you guys say. So I need it to be accurate to 1.80V only, that is good enough. Frequency should be like 3000.0Hz accurate.

Unfortunately not. The cheap devices (new or used) are no good. Really get something like the FY6900 or UTG932E. Getting a sine wave out of these is very simple and the level is reasonable accurate (say within 2% of the level at audio frequencies). Good enough to check whether your acquisition system is doing what you expect.

[gf]

Even your FNIRSI is possibly good enough for your use case.
Set the generator to 50Hz sine wave and adjust the output voltage until you mease 1V AC with your multimeter.
Then attach a 100 kOhm : 1 Ohm voltage divider and you have a 10µV source.

[shapirus]

Unfortunately not. The cheap devices (new or used) are no good.

Certainly more than good enough. If we read between lines, then e.g. a JDS2800 should work just fine. The microvolt and microhertz accuracy requirement is an obvious nonsense: the OP seems to not know exactly what he needs. I bet he just needs a basic signal generator that's good enough to be a starting point. Plus, of course, a DMM, one that can measure AC with a reasonable accuracy in the required frequency range, is also needed for fine tuning, and a basic oscilloscope would be nice to have as well.
But even without the DMM and oscilloscope, the JDS2800 is decently good, voltage-wise to about 10-30 mV (set 1.8 Vpp, measure RMS; set 5.091 Vpp, measure RMS). Frequency-wise it's even better: match down to 6th digit when measured by Rigol DHO800 (not that they can't be off by the same amount of course -- would need say a GPSDO to verify this).

All of the above is valid only as long as we consider any sane practical application, of course.

[loop123]

The OP probably does not understand that the output load needs to be 50 ohm. If you not load the generator with 50 ohm the output voltage is usually double the output voltage you set on the generator.

Or for the el cheapo chinese the unloaded output is the set voltage and as soon as you put a load on the output the voltage drops.

Benno

The E1DA ADC has input impedance of 640 Ohm while the Scaler has input impedance of 200k Ohm. What would happen to the signal generator with 50 ohm output impedance in them?

My multimeter has this specs up to 500Hz only. What best inexpensive multimeter that can measure at least 10Hz to 20000Hz with accuracy of 1/100000th (ops, i mean just accurate enough in 2.01V or 3000.01 Hz?

[ebastler]

My multimeter has this specs up to 500Hz only. What best inexpensive multimeter that can measure at least 10Hz to 20000Hz with accuracy of 1/100000th (ops, i mean just accurate enough in 2.01V or 3000.01 Hz?

As already suggested above, the Uni-T UT61E (or the newer UT161E) comes close, but does not quite meet your most recent requirements:

• Specified up to 10 kHz
• AC voltage accuracy +- 0.8% up to 1 kHz, +- 1.2% up tp 10 kHz, hence about 2V +- 0.02V (depending on frequency) for your example.
• Frequency accuracy is +- 0.01%, hence 3000 Hz +- 0.3 Hz for your example.

The UT61E should be available below $100, the newer 161E a bit over $100. The "E" suffix is important! The other UT61 or UT161 variants have significantly worse accuracy and resolution.

Maybe there is a "better AC multimeter" in this price range, but I am not aware of one.