Author Topic: Looking for a dynamic signal analyzer with extended bandwidth  (Read 4552 times)

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Offline _Wim_

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #50 on: June 15, 2018, 06:12:40 am »
I calculated the ENOBs for your scope.

16bit@2mV/div@20MHzLIMIT yields 6.19bits ENOB
16bit@200mV/div@20MHzLIMIT yields 8.86bits ENOB

So if you were to use the preamp, a maximum of approx. 2.5bits ENOB could be gained depending on the noise of the preamp.

2.5 bits ENOB is quite significant, not (16.8db). Off course the preamp add distorsion, so it depends on what is more important..
 

Offline thanasisk

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #51 on: June 15, 2018, 10:57:30 pm »
After seeings several measurements here (many thanx wim and egonotto!) and in the picoscope support forum, i can see that the 5000 series yield approx 7-10 bits of enob across ranges (1 bit of which is because of the bandwidth limit) which can be further improved  by 1.5 bits with res.enhancement and 1-1.5 bits by using a preamp. The dynamic range would be limited by distortion to around 67dB).

As for the 4262 I am wondering about the noise across ranges with and without bandwidth limit and with/without res enhancement. Perhaps egonotto you could kindly offer some further insight/measurements?
 

Offline Marco

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #52 on: June 15, 2018, 11:32:38 pm »
Eyeballing the FFT, I'd say the Red Pitaya has around the same dBFs noise on the 2Vpp input as the 5000, but is more linear.
 

Offline _Wim_

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #53 on: June 16, 2018, 01:09:42 am »
Eyeballing the FFT, I'd say the Red Pitaya has around the same dBFs noise on the 2Vpp input as the 5000, but is more linear.

Unfortunately the Red Pitaya lacks low input ranges, which makes it less usefull for my application. Combined with the preamp this could have been a potential candidate, but the preamp also introduces additional distorsion...

How is the software for the red pitaya? The hardware seems very capable for the price, but I am not sure how good the software is.
 

Offline egonotto

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #54 on: June 16, 2018, 01:15:35 am »
Hello,

Marco writes: "but is more linear."
What do you mean with this.

I think Red Pitaya has good hardware, but the software is frugal.

The Red Pitaya has 16kB/channel. If one would get knowledge about the noise you should consider the whole 16kB.

Best regards
egonotto
 

Offline Marco

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #55 on: June 16, 2018, 01:29:22 am »
What do you mean with this.
Their FFT of a 0dBm 2 MHz signal seems to show less harmonics than the one Wim showed for 1 MHz. Although on second thought, that might be the fault of the Rigol DG1032Z Wim used.
 

Offline _Wim_

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #56 on: June 16, 2018, 01:38:15 am »
Although on second thought, that might be the fault of the Rigol DG1032Z Wim used.

Unfortunately, that is the best (and only siggen I have that can produce a 1MHz signal. I do have somewhere a very low THD 10Khz audio oscillator, but I do not think this will prove much. Maybe egonotto has a very clean siggen to make the comparison?
 

Offline egonotto

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #57 on: June 16, 2018, 02:06:58 am »
Hello.

_Wim_ wrote: "How is the software for the red pitaya? The hardware seems very capable for the price, but I am not sure how good the software is"

I think it is possible to try if you want.
You can use my Red Pitaya over web. My version now is 0.94

Best regards
egonotto
 

Offline _Wim_

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #58 on: June 16, 2018, 03:36:20 am »
Hello.

_Wim_ wrote: "How is the software for the red pitaya? The hardware seems very capable for the price, but I am not sure how good the software is"

I think it is possible to try if you want.
You can use my Red Pitaya over web. My version now is 0.94

Best regards
egonotto

Thanks for the offer, but for the moment it is not necesarry. I was more wondering how the software was, as devices like this (and also the pico) only have real value is the software is up to the task...
 

Offline innkeeper

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #59 on: June 16, 2018, 04:31:59 am »
look into CMU-B41 for cmu200
Hobbyist and retired engeneer.
 

Offline egonotto

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #60 on: June 16, 2018, 04:51:10 am »
Hello,

here are some picture from PicoScope 4262. Both inputs have a 50 Ohm closure (without the noise in 10mV  would be far more)
Today the noise in 10mV RMS range is particular low most it is near 8.5 uV
The quotient p-p/RMS is very high. Much higher as other oszilloscope have. Look the excellent test from nctnico "http://www.eevblog.com/forum/testgear/rohde-schwarz-rtm3000-review/".

Best regards
egonotto


 
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Offline thanasisk

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #61 on: June 16, 2018, 10:24:53 am »
So I can see that the 4262 delivers ENOB of 9..12 bits across ranges (BW limit does not appear to have a huge effect on the outcome), which can be increased to 10..14 bits using hi-res mode.

That is 2 extra bits compared to a BW limited 5000.  :clap:
 

Offline _Wim_

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #62 on: June 16, 2018, 05:12:22 pm »
look into CMU-B41 for cmu200

If you mean as a signal generator, this one is quite limited. It only goes up to 20Khz, and THD+N is around 80dB. A sound card on a pc performs better then this.
 

Offline _Wim_

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #63 on: June 16, 2018, 06:01:24 pm »
Hello,

here are some picture from PicoScope 4262. Both inputs have a 50 Ohm closure (without the noise in 10mV  would be far more)
Today the noise in 10mV RMS range is particular low most it is near 8.5 uV
The quotient p-p/RMS is very high. Much higher as other oszilloscope have. Look the excellent test from nctnico "http://www.eevblog.com/forum/testgear/rohde-schwarz-rtm3000-review/".

Best regards
egonotto

Thanks for the additional measurements. Looking at the tests of nctnico, I was a bit supprized the noise levels were much higher with the 50ohm input impedance. As expected before, the 4262 is indeed still much better then the 5000 series. If only it had a little more bandwidth.

The RTM3000 also looks like an excellent device, but is above the level I want to spent...
 

Offline egonotto

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #64 on: June 17, 2018, 05:26:16 am »
Hello,

sometimes one can the improve the noise through addition the same signal.

Best regards
egonotto

« Last Edit: June 17, 2018, 05:29:38 am by egonotto »
 

Offline thanasisk

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #65 on: June 17, 2018, 06:48:57 am »
Hello,

sometimes one can the improve the noise through addition the same signal.

Best regards
egonotto

This is a cool idea. You could even squeeze some more SNR  if you compensate for dc offset  and weight each channel according to the rms noise.  Not sure if the math channel of picoscope could support this though.
 

Offline nctnico

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #66 on: June 17, 2018, 07:09:45 am »
Hello,

here are some picture from PicoScope 4262. Both inputs have a 50 Ohm closure (without the noise in 10mV  would be far more)
Today the noise in 10mV RMS range is particular low most it is near 8.5 uV
The quotient p-p/RMS is very high. Much higher as other oszilloscope have. Look the excellent test from nctnico "http://www.eevblog.com/forum/testgear/rohde-schwarz-rtm3000-review/".

Best regards
egonotto

Thanks for the additional measurements. Looking at the tests of nctnico, I was a bit supprized the noise levels were much higher with the 50ohm input impedance. As expected before, the 4262 is indeed still much better then the 5000 series. If only it had a little more bandwidth.

The RTM3000 also looks like an excellent device, but is above the level I want to spent...
That has to do with the lower bandwidth of the inputs in 1M Ohm mode With the 20MHz bandwidth limit on the 50 Ohm mode on the RTM3000 has a much lower noise floor.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline _Wim_

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #67 on: June 17, 2018, 03:20:30 pm »
That has to do with the lower bandwidth of the inputs in 1M Ohm mode With the 20MHz bandwidth limit on the 50 Ohm mode on the RTM3000 has a much lower noise floor.

I was looking at the bandwidth limited case! But I see now, the name of the pictures are mixed up, and I was unsure how to interprete the channel setup "DC" and "Ohm"...
 

Offline _Wim_

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #68 on: June 17, 2018, 03:43:04 pm »
But I see now, the name of the pictures are mixed up

In that case, with 20M BWLimit and 1M input, the RTM is noiser than the pico5000 (Vrms 33µV vs 63µV, Vpp 321µV vs 518µV). But the pico does not have 50ohm input impedance (not very usefull for me because of too much loading), so this comparison cannot be made.
 

Online David Hess

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #69 on: June 17, 2018, 10:51:12 pm »
In that case, with 20M BWLimit and 1M input, the RTM is noiser than the pico5000 (Vrms 33µV vs 63µV, Vpp 321µV vs 518µV). But the pico does not have 50ohm input impedance (not very usefull for me because of too much loading), so this comparison cannot be made.

Is there any way to determine how much of that is input noise and how much is quantization noise?

33uVrms over 20MHz is high for a 1Mohm input but may be consistent with a CMOS implementation.
 

Offline bozidarms

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #70 on: June 18, 2018, 03:26:27 am »
HP 89410A continue to be the most noiseless analyzer till this days - effective about only 8 nV/√Hz,
better that some dedicated LNA-s!
 

Offline _Wim_

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #71 on: June 18, 2018, 04:07:07 am »
HP 89410A continue to be the most noiseless analyzer till this days - effective about only 8 nV/√Hz,
better that some dedicated LNA-s!

 8 nV/√Hz equals to 35µVrms at 20MHz bandwidth, so that is quite simular than the pico. Is that for the 50 ohm input or for the 1Mohm input? But I agree it is a very nice analyzer, and if I lived in the states, I would probably have bought this one instead of the pico. But in Europe these are much more expensive, and shipping a beast like that aint cheap...
 

Offline bozidarms

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #72 on: June 18, 2018, 04:41:24 am »
For 1Mega ohm.
Yes, still one exceptional instrument indeed, unfortunately expensive in EU.
 

Offline Gerhard_dk4xp

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #73 on: June 18, 2018, 09:56:12 am »
HP 89410A continue to be the most noiseless analyzer till this days - effective about only 8 nV/√Hz,
better that some dedicated LNA-s!

Aaarghhh! - No!

Below 100 Hz its 1/f noise is breathtaking. For my low noise amplifiers,
an 80 dB preamp is not enough to mask it. Rising the gain above 80 dB
is impossible because of overflows. And the preamp has 200pV/rt Hz.

regards, Gerhard

(none the less, I kinda like it. Contact me if you want a remote control
C/Linux program to do FFT plots over 9 decades via network.
Requires Gnuplot.)
« Last Edit: June 18, 2018, 10:00:32 am by Gerhard_dk4xp »
 

Offline _Wim_

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Re: Looking for a dynamic signal analyzer with extended bandwidth
« Reply #74 on: June 19, 2018, 05:27:23 am »
For my low noise amplifiers,  an 80 dB preamp is not enough to mask it. Rising the gain above 80 dB
is impossible because of overflows. And the preamp has 200pV/rt Hz.

Nice pre-amp! That sure beats my 5113 in noise for low impedance sources, looks ideaal for power supply noise measurements!

For others,  see here: http://www.hoffmann-hochfrequenz.de/downloads/lono.pdf
 


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