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| Oscilloscope input noise comparison |
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| jpb:
I am interested in these Picoscope results as I'm thinking of getting the 4262 for ADEV and phase noise type measurements but would like more than 2 channels if possible. I have a couple of questions. Looking at the data sheet for the 5000 series, it looks as if 16bit mode only works with 1 channel - is this correct? (i.e. if you're in 16 bit mode you can only have one out of four channels operational) If it is correct, then for 16 bit (below 5MHz) you can't get more than 2 channels (4262) anyway. Secondly, the relatively noisy plots you posted _Wim_ are labelled "shorted" while the plots you posted Performa01 are labelled as being terminated in 50 ohms. The input impedance of the scopes is 10M not 50 ohms but I wondered if this made a difference or perhaps "shorted" just means a 50 ohm terminator anyway. |
| 2N3055:
3406D MSO 500MSa/s from 1kHz to 200MHz 50 Ohm terminator on input (I didn't have a short handy) |
| Performa01:
--- Quote from: jpb on December 26, 2018, 11:30:47 am ---Looking at the data sheet for the 5000 series, it looks as if 16bit mode only works with 1 channel - is this correct? (i.e. if you're in 16 bit mode you can only have one out of four channels operational) If it is correct, then for 16 bit (below 5MHz) you can't get more than 2 channels (4262) anyway. --- End quote --- Yes. You can get more than 2 channels only in 14 bit mode. But then, the 15 and 16 bit modes appear to be extreme trickery and I don’t see a real advantage using them. I think that the 4262 is rather unique and cannot be compared to the 5000 series scopes in any way. Just look at the dynamic performance specifications in the data sheet to get the idea. 5000 series 4262 Crosstalk >400:1 >50000:1 Harmonic Distortion -70 dB (≥12 bit) -95 dB SFDR 70 dB (≥14 bit) 96 dB Noise 70 µV RMS (16 bit) 8.5 µV RMS --- Quote from: jpb on December 26, 2018, 11:30:47 am ---Secondly, the relatively noisy plots you posted _Wim_ are labelled "shorted" while the plots you posted Performa01 are labelled as being terminated in 50 ohms. The input impedance of the scopes is 10M not 50 ohms but I wondered if this made a difference or perhaps "shorted" just means a 50 ohm terminator anyway. --- End quote --- Input short or 50ohm terminator don’t make a difference at that level. --- Quote from: 2N3055 on December 26, 2018, 11:54:40 am ---3406D MSO 500MSa/s from 1kHz to 200MHz 50 Ohm terminator on input (I didn't have a short handy) --- End quote --- Yes, this is much improved over the older 3000 series. Higher input sensitivity, switchable 20MHz bandwidth limit, twice the ADC sample rate… Interesting to see the much reduced spurious signals and the spur at 31.25MHz is missing altogether. Probably because of the doubled ADC speed, whereas the various physical sampling speeds in the 5000 series might have different clocking requirements. |
| _Wim_:
--- Quote from: jpb on December 26, 2018, 11:30:47 am ---Looking at the data sheet for the 5000 series, it looks as if 16bit mode only works with 1 channel - is this correct? --- End quote --- Yes, but 16 bit mode makes no real sense for this scope. Above 14 bit there is no performance increase noise floor wise, and give you already 84 db theoretical, with an SFDR or only 70dB, this is more than sufficient. In 14 bit you can use all 4 channels up to 60Mhz. But as stated above, the 4262 has much higher performance than the 5000, but lacks the bandwidth. Depending on your needs, this can be important or not. --- Quote from: jpb on December 26, 2018, 11:30:47 am ---Secondly, the relatively noisy plots you posted _Wim_ are labelled "shorted" while the plots you posted Performa01 are labelled as being terminated in 50 ohms. The input impedance of the scopes is 10M not 50 ohms but I wondered if this made a difference or perhaps "shorted" just means a 50 ohm terminator anyway. --- End quote --- I was using a short, not 50 ohm terminator. I have use a 50 ohm terminator in the past also, but result were indentical. |
| _Wim_:
--- Quote from: Performa01 on December 26, 2018, 12:38:19 pm ---[Yes, this is much improved over the older 3000 series. Higher input sensitivity, switchable 20MHz bandwidth limit, twice the ADC sample rate… Interesting to see the much reduced spurious signals and the spur at 31.25MHz is missing altogether. Probably because of the doubled ADC speed, whereas the various physical sampling speeds in the 5000 series might have different clocking requirements. --- End quote --- Indeed, the 3406D perform quite wel, I am impressed. Still dreaming of an 4262 with the bandwidth of the 5000 series (that is also affordable ::) ) |
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