Products > Test Equipment
Decent modern Signal/waveform Generator here in early 2024
nctnico:
--- Quote from: 2N3055 on January 08, 2024, 07:25:12 pm ---
--- Quote from: cncjerry on January 08, 2024, 06:05:04 pm ---Only issue with the Siglent 1032x, which is upgraded in my case, is the frequency resolution isn't as expected. I need a 10,000,001hz signal and even with a common reference, it is measured as 10,000,000.988hz. I think I read that the resolution is .023hz. I have other synthesizers, some over 30yrs old, that get a lot closer with resolution to .001hz
--- End quote ---
That is because it is not a synthesizer, it is NCO.
And none of modern AWG will be synthesizers in classical sense with PLL dividers and such.
If there are some, you bet it will be obviously stated in a datasheet.
Data you stated would mean frequency setting resolution of 23 ppb....
--- End quote ---
That is only one sample point. Without knowing the guaranteed significant digits for the frequency setting, you don't know how big the error is worst case. In the end the DDS has a finite number of bits; the error between wanted and actual frequency depends on that and this error can be much bigger than 23ppb. It is like a divider based baudrate generator. Some frequencies can be created perfectly, other frequencies have a significant error.
2N3055:
--- Quote from: nctnico on January 09, 2024, 03:29:34 pm ---
--- Quote from: 2N3055 on January 08, 2024, 07:25:12 pm ---
--- Quote from: cncjerry on January 08, 2024, 06:05:04 pm ---Only issue with the Siglent 1032x, which is upgraded in my case, is the frequency resolution isn't as expected. I need a 10,000,001hz signal and even with a common reference, it is measured as 10,000,000.988hz. I think I read that the resolution is .023hz. I have other synthesizers, some over 30yrs old, that get a lot closer with resolution to .001hz
--- End quote ---
That is because it is not a synthesizer, it is NCO.
And none of modern AWG will be synthesizers in classical sense with PLL dividers and such.
If there are some, you bet it will be obviously stated in a datasheet.
Data you stated would mean frequency setting resolution of 23 ppb....
--- End quote ---
That is only one sample point. Without knowing the guaranteed significant digits for the frequency setting, you don't know how big the error is worst case. In the end the DDS has a finite number of bits; the error between wanted and actual frequency depends on that and this error can be much bigger than 23ppb. It is like a divider based baudrate generator. Some frequencies can be created perfectly, other frequencies have a significant error.
--- End quote ---
Actually, just quickly tried..
I can set 10ppb of set frequency at 10 Mhz and 100Mhz. Dead accurately. That is 10 µHz resolution at 10 Mhz.
I typed in 10.000 000 43 MHz and got exactly that. I cannot go better than that at this moment, 10 digits is limit of counter i have here.
Later I will check in more detail...
For Tektronix you have I see specification of: Frequency accuracy ±10-6 of setting (all except ARB)
It is obviously more complicated than simple number.
But my point is : those are set frequency resolutions in ppb.... Why is that an issue on 340 € AWG with +- 25 ppm initial frequency accuracy...???
DaneLaw:
How accurate are these 10Mhz reference in/out sources on entry test-gear, like modern DDS-based signal generators.
Got a reading that looks like +40Hz by taking the 10Mhz in/out up the Rigol unit's own counter., is that more or less what to expect on entry units in the sub 300 price cat or more the counters limitasions'
nctnico:
--- Quote from: DaneLaw on January 13, 2024, 05:48:17 pm ---How accurate are these 10Mhz reference in/out sources on entry test-gear, like modern DDS-based signal generators.
Got a reading that looks like +40Hz by taking the 10Mhz in/out up the Rigol unit's own counter., is that more or less what to expect on entry units in the sub 300 price cat or more the counters limitasions'
--- End quote ---
It could be the counter, it could be the generator. A quick test for generators with two or more channels is to have it output 2 frequencies at exact multiples but far apart. Like 1Hz and 10MHz. Then trigger an oscilloscope on the lower frequency. Most of the sub 1000 euro generators I tested show a drift on the higher frequency indicating there is a frequency offset between them. Also locking to a 10MHz source properly is something you shouldn't expect to work flawlessly (as in no frequency offset).
It doesn't mean low cost function generators are bad but you have to be aware of their limitations where it comes to frequency accuracy (which -again- is typically not specified on sub 1000 euro generators).
2N3055:
--- Quote from: nctnico on January 14, 2024, 06:40:54 pm ---
--- Quote from: DaneLaw on January 13, 2024, 05:48:17 pm ---How accurate are these 10Mhz reference in/out sources on entry test-gear, like modern DDS-based signal generators.
Got a reading that looks like +40Hz by taking the 10Mhz in/out up the Rigol unit's own counter., is that more or less what to expect on entry units in the sub 300 price cat or more the counters limitasions'
--- End quote ---
It could be the counter, it could be the generator. A quick test for generators with two or more channels is to have it output 2 frequencies at exact multiples but far apart. Like 1Hz and 10MHz. Then trigger an oscilloscope on the lower frequency. Most of the sub 1000 euro generators I tested show a drift on the higher frequency indicating there is a frequency offset between them. Also locking to a 10MHz source properly is something you shouldn't expect to work flawlessly (as in no frequency offset).
It doesn't mean low cost function generators are bad but you have to be aware of their limitations where it comes to frequency accuracy (which -again- is typically not specified on sub 1000 euro generators).
--- End quote ---
Synthesized frequency resolution is usually specified on most of them to the point of being better than frequency stability of timebase (initial accuracy, drift, tempco) which will be largest contributor to frequency accuracy..
But, he is connecting AWG internal 10MHz ref out to AWG internal counter, that is running from the same reference I presume... It should count exactly 10.000000 or maybe one last count up down... It is self referenced.
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