Author Topic: The Siglent SDG2042X Thread  (Read 273337 times)

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Offline Timpert

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Sinewave signal quality
« Reply #275 on: March 03, 2016, 04:55:54 pm »
I was wondering, has anyone actually checked the quality of the sinewave (harmonic distortion, spurious output) beyond the amplitude at which it is specified (0 dBm or 223 mV in 50 Ohms). How does the thing behave when it is cranked up to the max?

Edit: I have to add the word "quantify". Like assess harmonics on a spectrum analyzer.
« Last Edit: March 03, 2016, 07:39:17 pm by Timpert »
 

Offline mongo

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Re: The Siglent SDG2042X Thread
« Reply #276 on: March 03, 2016, 10:33:47 pm »
While I don't have a  spectrum analyzer the FFT shows no major harmonics on my little agilent dsox2012a.  I am working on an AM radio today pushing 7.1V peak to peak and it is quite happy at low frequencies, I have attached an ugly pic on when I was trying to get it to sync to the built in generator on the dsox2012a, while this is ugly with jitter the yellow line is at 8MHz and pretty much maxed out.


Obviously if you look at this pic you will realize I wasn't too serious about measuring but it is pretty good.  Hopefully someone with better tools will respond but I am quite happy with it.  You should temper that with the understanding that I just replaced a HP 3311A with this device.  I did beak out the HP because I thought that I had forgotten how to do FFT and it was a lot worse.  This unit is as good as I would expect a 16-bit unit to be.  I have been using it as a DC source, mostly because my bigger supplies have loud fans and I can't see anything out of the normal environmental noise on my Keithley 2100 DMM.

Outside of some software issues, which I think they will fix and which do not hurt my use case, the main limiter of this unit is accurate time.  I have been shopping for parts to build a 10 MHz OCXO-based GPS disciplined oscillator but that won't fix the issues with my low end scope unless I am missing an menu some place.

Note above that this was not a serious test, and that I was actually testing the jitter on my dsox2012a.


 

Offline uncle_bob

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Re: Sinewave signal quality
« Reply #277 on: March 04, 2016, 12:22:03 am »
I was wondering, has anyone actually checked the quality of the sinewave (harmonic distortion, spurious output) beyond the amplitude at which it is specified (0 dBm or 223 mV in 50 Ohms). How does the thing behave when it is cranked up to the max?

Edit: I have to add the word "quantify". Like assess harmonics on a spectrum analyzer.

Hi

Like a lot of signal generators (but not an old style function generator. This guy has a set of attenuators in it. As you crank the level, you can hear the relays going click click click every 6 db or so. Because of that, I doubt there is a lot of difference between 0 dbm and "near max out" sort of levels. It's running over the same (full out to ~ half max voltage) range again and again. The attenuators simply drop things down as you reduce the level.

Bob
 

Offline smgvbest

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Re: The Siglent SDG2042X Thread
« Reply #278 on: March 04, 2016, 08:42:13 pm »
I'm still learning the use of a SA so hopefully I did these correctly
Siglent at 120Mhz, 5vpp max out output

Sandra
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Offline markone

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Re: The Siglent SDG2042X Thread
« Reply #279 on: March 04, 2016, 09:21:40 pm »
I'm still learning the use of a SA so hopefully I did these correctly
Siglent at 120Mhz, 5vpp max out output

I would use much lower RBW values, for instance :

- full span sweep (1.5Ghz ?) with 10Khz RBW
- 100 Khz span sweep with 100Hz RBW
 

Offline bson

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Re: The Siglent SDG2042X Thread
« Reply #280 on: March 05, 2016, 04:25:23 am »
Sitting here with a brand new 2122X on the bench - nice little generator.  Updated it to the latest firmware (#17).

I do have a bit of a firmware dislike... it doesn't remember that it's set to use an external 10MHz reference across power cycles even if set to use the last settings at power on.  Not only does it ignore the external clock, but it merrily outputs its own internal timebase onto the cable and fights with my GPSDO!  Plus the 53131A counter alarms about the timebase being changed, and my VNA doesn't like it.  So I unplug the cable from the 2122X after powering off.  The only problem is I can't set it to use the external reference without plugging the cable in, and when I do the instrument outputs its own clock until I can toggle it using the front panel.  It's also not possible to tell it to use the external reference before plugging it in.

Anyway, my suggestion would be:

1. Remember the setting...
2. Even better, auto-detect on power-up or before enabling the clock output to make sure there isn't already a clock source on the cable and use the external timebase if enabled
 

Online tautech

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Re: The Siglent SDG2042X Thread
« Reply #281 on: March 05, 2016, 05:38:18 am »
Sitting here with a brand new 2122X on the bench - nice little generator.  Updated it to the latest firmware (#17).

I do have a bit of a firmware dislike... it doesn't remember that it's set to use an external 10MHz reference across power cycles even if set to use the last settings at power on.  Not only does it ignore the external clock, but it merrily outputs its own internal timebase onto the cable and fights with my GPSDO!  Plus the 53131A counter alarms about the timebase being changed, and my VNA doesn't like it.  So I unplug the cable from the 2122X after powering off.  The only problem is I can't set it to use the external reference without plugging the cable in, and when I do the instrument outputs its own clock until I can toggle it using the front panel.  It's also not possible to tell it to use the external reference before plugging it in.

Anyway, my suggestion would be:

1. Remember the setting...
2. Even better, auto-detect on power-up or before enabling the clock output to make sure there isn't already a clock source on the cable and use the external timebase if enabled

Good ideas, I pass them on to R&D.
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Offline uncle_bob

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Re: The Siglent SDG2042X Thread
« Reply #282 on: March 05, 2016, 03:09:07 pm »
Sitting here with a brand new 2122X on the bench - nice little generator.  Updated it to the latest firmware (#17).

I do have a bit of a firmware dislike... it doesn't remember that it's set to use an external 10MHz reference across power cycles even if set to use the last settings at power on.  Not only does it ignore the external clock, but it merrily outputs its own internal timebase onto the cable and fights with my GPSDO!  Plus the 53131A counter alarms about the timebase being changed, and my VNA doesn't like it.  So I unplug the cable from the 2122X after powering off.  The only problem is I can't set it to use the external reference without plugging the cable in, and when I do the instrument outputs its own clock until I can toggle it using the front panel.  It's also not possible to tell it to use the external reference before plugging it in.

Anyway, my suggestion would be:

1. Remember the setting...
2. Even better, auto-detect on power-up or before enabling the clock output to make sure there isn't already a clock source on the cable and use the external timebase if enabled

Hi

That does make the generator totally useless with an external standard doesn't it?

The default should be "nothing out the back". Just have it sit there waiting to be told what to do if it can't remember what the last state was. An enabled output is a "really bad thing" even or a not external ref in situation. You now have one more spurious signal crawling all over your bench.

Bob
 

Offline bson

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Re: The Siglent SDG2042X Thread
« Reply #283 on: March 05, 2016, 09:46:51 pm »
That does make the generator totally useless with an external standard doesn't it?
Actually, it does.  I considered plugging it into a Symmetricom distribution tap, but those are pretty beefy; they won't be harmed by the Siglent, but the Siglent could possibly be damaged if it uses a basic push-pull driver.  If the tap pushes when the Siglent pulls I doubt the tap will too inclined to droop... it'll perhaps just source a few amps into the Siglent during that portion of the phases aligning badly.

Quote
The default should be "nothing out the back". Just have it sit there waiting to be told what to do if it can't remember what the last state was. An enabled output is a "really bad thing" even or a not external ref in situation. You now have one more spurious signal crawling all over your bench.
Agree.  The best would be able to turn it off altogether.  And remember this setting across power cycles. :)  Or if it can't be remembered, default to it shutting off on power cycle so it needs to be explicitly reenabled.
« Last Edit: March 05, 2016, 09:49:58 pm by bson »
 

Offline bson

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Re: The Siglent SDG2042X Thread
« Reply #284 on: March 06, 2016, 01:57:19 am »
And, just because I could... using a VNA as an SA. :)

2122X set to 24.576132MHz using internal timebase
-20dBm output level
The spec says -55dBc spectral purity at this frequency.  I was skeptical this would truly be relative to the carrier (dBc) and thought they might mean relative to peak output (5Vpp).

Good old VNA set to 100Hz span centered on 24.576135MHz (just the peak the marker found at RBW=10, set to center)
100Hz span
1Hz RBW
40 sec sweep (!!!)
10dB/div V
10Hz/div H

This instrument is not the most agile at such a narrow span and 1Hz RBW... kind of pushing it.
It reports a peak at 24576133.5... My 53131A counter indicates it's 24576132.45Hz, so the VNA is off just a smidgeon over 1 full sweep step.

But... looks like the 2122X handily passes the spec of -55dBc for 20-40MHz.

Didn't grab a shot at RBW 10Hz, but it looks very similar, just tighter and more evenly stepped.



EDIT - here's a better one with a 100sec sweep time (4 sweeps averaged); for some reason the 3577A didn't like a 100sec sweep time until it was fully warmed up.  Checking with the marker, -55dBc intersects at 5.5Hz on the high side and 6Hz on the low side.


« Last Edit: March 06, 2016, 02:22:16 am by bson »
 

Offline uncle_bob

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Re: The Siglent SDG2042X Thread
« Reply #285 on: March 06, 2016, 02:04:46 am »
And, just because I could... using a VNA as an SA. :)

2122X set to 24.576132MHz using internal timebase
-20dBm output level
The spec says -55dBc spectral purity at this frequency.  I was skeptical this would truly be relative to the carrier (dBc) and thought they might mean relative to peak output (5Vpp).

Good old VNA set to 100Hz span centered on 24.576135MHz (just the peak the marker found at RBW=10, set to center)
100Hz span
1Hz RBW
40 sec sweep (!!!)
10dB/div V
10Hz/div H

This instrument is not the most agile at such a narrow span and 1Hz RBW... kind of pushing it.
It reports a peak at 24576133.5... My 53131A counter indicates it's 24576132.45Hz, so the VNA is off just a smidgeon over 1 full sweep step.

But... looks like the 2122X handily passes the spec of -55dBc for 20-40MHz.

Didn't grab a shot at RBW 10Hz, but it looks very similar, just tighter and more evenly stepped.



Hi

Based on the fact that they have a proper attenuator in the instrument that's not a real surprising outcome. Once you hit the floor of the attenuator (1 mv out if I remember correctly) then indeed your signal to noise in dbc is going to degrade as power drops. Simple answer ... get a couple of 20 db external coaxial pads and use them below 1 mv.

At some point the leakage from a simple box instrument is going to wipe you out on low signal level stuff. A generator that is legit at -127 dbm out has a lot more shielding in it than this guy does. It also costs ... a bit ... more. It's also quite a bit bigger and heavier. Last time I broke one, the repair charge would have bought a skid full of these little guys.

Hint: Relay based attenuators don't like it when you switch power once a second for a month.....

Bob
 

Offline bson

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Re: The Siglent SDG2042X Thread
« Reply #286 on: March 06, 2016, 02:40:37 am »
Based on the fact that they have a proper attenuator in the instrument that's not a real surprising outcome. Once you hit the floor of the attenuator (1 mv out if I remember correctly) then indeed your signal to noise in dbc is going to degrade as power drops. Simple answer ... get a couple of 20 db external coaxial pads and use them below 1 mv.
Ah, so that's why there's clicking when you change levels...
 

Offline mojoe

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Re: The Siglent SDG2042X Thread
« Reply #287 on: March 06, 2016, 07:10:20 am »
Sitting here with a brand new 2122X on the bench - nice little generator.  Updated it to the latest firmware (#17).

I do have a bit of a firmware dislike... it doesn't remember that it's set to use an external 10MHz reference across power cycles even if set to use the last settings at power on.  Not only does it ignore the external clock, but it merrily outputs its own internal timebase onto the cable and fights with my GPSDO!  Plus the 53131A counter alarms about the timebase being changed, and my VNA doesn't like it.  So I unplug the cable from the 2122X after powering off.  The only problem is I can't set it to use the external reference without plugging the cable in, and when I do the instrument outputs its own clock until I can toggle it using the front panel.  It's also not possible to tell it to use the external reference before plugging it in.

Anyway, my suggestion would be:

1. Remember the setting...
2. Even better, auto-detect on power-up or before enabling the clock output to make sure there isn't already a clock source on the cable and use the external timebase if enabled

Good ideas, I pass them on to R&D.

I vote for number 2. That is the way a lot of high dollar gear does it. If there is an external reference plugged in, use it. If not, switch on the internal reference. This is easy and won't damage anything.
 

Offline bson

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Re: The Siglent SDG2042X Thread
« Reply #288 on: March 06, 2016, 10:35:04 pm »
I vote for number 2. That is the way a lot of high dollar gear does it. If there is an external reference plugged in, use it. If not, switch on the internal reference. This is easy and won't damage anything.
Yeah, #2 is the better choice - more specifically, use the external reference if plugged in otherwise use the internal and don't ever output anything on the port until asked to.

However, this may not be so simple from a firmware perspective; it may not be practical to continuously poll to check if there's an external reference and may require switching the internal clock PLL to it to see if lock can be acquired - which would disrupt ongoing waveform generation.  If this is the case, then I'd be fine with it being done automatically at startup only; recabling the bench and changing out the extref source is fine to require a power cycle or manual reconfig, it's so rare anyway.  In my case, at least.  But in this case there's not much use doing anything automatically - just allow it to be set and remember it.
 

Offline bson

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Re: The Siglent SDG2042X Thread
« Reply #289 on: March 06, 2016, 10:39:53 pm »
Oh, and also: as a safety precaution, before enabling the output check to see if there's already a signal on the port.  If so, alert to it and refuse to enable the output.
 

Offline uncle_bob

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Re: The Siglent SDG2042X Thread
« Reply #290 on: March 07, 2016, 12:01:33 am »
I vote for number 2. That is the way a lot of high dollar gear does it. If there is an external reference plugged in, use it. If not, switch on the internal reference. This is easy and won't damage anything.
Yeah, #2 is the better choice - more specifically, use the external reference if plugged in otherwise use the internal and don't ever output anything on the port until asked to.

However, this may not be so simple from a firmware perspective; it may not be practical to continuously poll to check if there's an external reference and may require switching the internal clock PLL to it to see if lock can be acquired - which would disrupt ongoing waveform generation.  If this is the case, then I'd be fine with it being done automatically at startup only; recabling the bench and changing out the extref source is fine to require a power cycle or manual reconfig, it's so rare anyway.  In my case, at least.  But in this case there's not much use doing anything automatically - just allow it to be set and remember it.


Hi

The last thing in the world you want is an instrument that randomly switches from internal to external standard based on some guess it is making. The only *safe* way to do it:

1) If it's set to external reference, check for the ref. If it is not there toss up a great big error message and stop.

2) If it's set to internal reference, don't check for any external device. Also don't put anything out the ref input.

3) If a ref output is desired, enable that independently of the internal ref setting. That way you can run the box without it being a spur monster.

4) If the box is running in default mode, make that internal ref / no external output.

If indeed you wish to provide some sort of auto sensing / auto switching / grab anything / do anything setup ... make that a distinct option after you get the "normal" stuff working as it should.

Why do it this way? If this is being used as a traceable signal source, in about 99% of the cases, it will have an external reference. If that ref goes away, you need to know about it right now. Back in the "good old days" epoxy was used on switches to force this to happen ....

Bob
 

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Re: The Siglent SDG2042X Thread
« Reply #291 on: March 07, 2016, 07:00:44 am »
I vote for number 2. That is the way a lot of high dollar gear does it. If there is an external reference plugged in, use it. If not, switch on the internal reference. This is easy and won't damage anything.
Yeah, #2 is the better choice - more specifically, use the external reference if plugged in otherwise use the internal and don't ever output anything on the port until asked to.

However, this may not be so simple from a firmware perspective; it may not be practical to continuously poll to check if there's an external reference and may require switching the internal clock PLL to it to see if lock can be acquired - which would disrupt ongoing waveform generation.  If this is the case, then I'd be fine with it being done automatically at startup only; recabling the bench and changing out the extref source is fine to require a power cycle or manual reconfig, it's so rare anyway.  In my case, at least.  But in this case there's not much use doing anything automatically - just allow it to be set and remember it.


Hi

The last thing in the world you want is an instrument that randomly switches from internal to external standard based on some guess it is making. The only *safe* way to do it:

1) If it's set to external reference, check for the ref. If it is not there toss up a great big error message and stop.

2) If it's set to internal reference, don't check for any external device. Also don't put anything out the ref input.

3) If a ref output is desired, enable that independently of the internal ref setting. That way you can run the box without it being a spur monster.

4) If the box is running in default mode, make that internal ref / no external output.

If indeed you wish to provide some sort of auto sensing / auto switching / grab anything / do anything setup ... make that a distinct option after you get the "normal" stuff working as it should.

Why do it this way? If this is being used as a traceable signal source, in about 99% of the cases, it will have an external reference. If that ref goes away, you need to know about it right now. Back in the "good old days" epoxy was used on switches to force this to happen ....

Bob
Bob, from Siglent tech support:
Yes, this idea is good, our R&D will get to know this.
Avid Rabid Hobbyist
 

Offline bson

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Re: The Siglent SDG2042X Thread
« Reply #292 on: March 07, 2016, 08:12:30 am »
Bob, from Siglent tech support:
Yes, this idea is good, our R&D will get to know this.
Awesome - thanks!!!  :-+
 

Offline mojoe

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Re: The Siglent SDG2042X Thread
« Reply #293 on: March 07, 2016, 05:10:09 pm »
I didn't mean for the siggen to switch references on the fly. Only at startup, as recommended in the post I was replying to.
 

Offline uncle_bob

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Re: The Siglent SDG2042X Thread
« Reply #294 on: March 07, 2016, 11:13:58 pm »
I didn't mean for the siggen to switch references on the fly. Only at startup, as recommended in the post I was replying to.

Hi

The lights go blink, the generator either does or does not reboot. The chain that feeds the external standard either does or does not reboot. Which one gets running first? Who knows ...It's also a problem on benches that have chained standards or a local distribution amplifier. You power up the whole bench at once. What happens? Again, it's only a guess as to what gets going first.

Bob
 

Offline pxl

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Re: The Siglent SDG2042X Thread
« Reply #295 on: March 25, 2016, 08:02:51 pm »
Guys, has anyone actually replaced the fan? Any experiences? Can you make scrambled eggs on it after the replacement? :)
 

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Re: The Siglent SDG2042X Thread
« Reply #296 on: March 25, 2016, 08:09:31 pm »
Guys, has anyone actually replaced the fan? Any experiences? Can you make scrambled eggs on it after the replacement? :)
What's the problem with the fan, noise?
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Offline pxl

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Re: The Siglent SDG2042X Thread
« Reply #297 on: March 25, 2016, 08:31:14 pm »
Guys, has anyone actually replaced the fan? Any experiences? Can you make scrambled eggs on it after the replacement? :)
What's the problem with the fan, noise?

Yes, it is definitely loud. No resonations, no bearing noise, it is just the normal airflow and with usual background noise/music it's not bad at all. But in a silent room it is loud. I will replace/slow down/temp control that fan in future in any case, just interested in with the experiences.
 

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Re: The Siglent SDG2042X Thread
« Reply #298 on: March 25, 2016, 08:57:45 pm »
Guys, has anyone actually replaced the fan? Any experiences? Can you make scrambled eggs on it after the replacement? :)
What's the problem with the fan, noise?

Yes, it is definitely loud. No resonations, no bearing noise, it is just the normal airflow and with usual background noise/music it's not bad at all. But in a silent room it is loud. I will replace/slow down/temp control that fan in future in any case, just interested in with the experiences.
Hmm, I'll check one from my new stock that's just arrived.

Do you have other equipment to compare it with so to give us an idea of noise level?
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Offline pxl

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Re: The Siglent SDG2042X Thread
« Reply #299 on: March 25, 2016, 09:18:06 pm »
It uses the same fan PAAD16025SL PF00, and actually I don't think that anything wrong with this unit. It's just I have no other device with fan :)

Anyway, for the first look the build quality is very good. It is easily par on my HMO1002, and the BNC outputs, the rotary switch are actually much better than my scope's, so it is pretty amazing. After an hour usage it is pretty cold, so I am sure there is some room for thermal optimisation in this unit. I will get an IR thermometer/FLIR and will measure the temps in it.

The firmware is 2.01.01.16R2.

However I set the beeper off (I like the silent :)), but it forgets after switch off :/
« Last Edit: March 25, 2016, 09:24:44 pm by pxl »
 


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