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| Oscilloscope input noise comparison |
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| David Hess:
Broadband noise of 10 nV/SqrtHz is about right. But noise at low frequencies increases due to 1/f or flicker noise which can be very high for integrated CMOS designs which are common now in DSOs. There is also additional low frequency Johnson noise from the parallel RC network in series with the input which provides overload protection. |
| maxwell3e10:
Yes, it would be interesting to have another set of data that spans the frequency range 10 Hz to 1MHz to measure 1/f noise. This would require using lower sample rate, about 1 MHz. |
| rsjsouza:
Interesting comparison. I can provide Rigol's DS4014 information. I am pretty sure it will be a lot higher than the average, but still worth taking it. |
| Performa01:
--- Quote from: maxwell3e10 on October 19, 2018, 02:12:07 pm ---Yes, it would be interesting to have another set of data that spans the frequency range 10 Hz to 1MHz to measure 1/f noise. This would require using lower sample rate, about 1 MHz. --- End quote --- The problem with a low sample rate like 1MSa/s is that all the noise above Nyquist (500kHz) will fold back and add to the result. This would severely distort the measurements, since a major part of noise energy would come from that folded back frequency range above 500kHz. Even with 20MHz bandwidth limit, it would still be 20MHz vs. 500kHz noise bandwidth. So my suggestion would be to use at least 100MSa/s in order to get a reasonable attenuation of the aliased frequency band by means of the 20MHz bandwidth limit. How low do we need (or want) to go with such a measurement? For 10Hz, we'd need 10ms/div timebase and at least 10Mpts of data, which we could not handle over this forum. You'd need to provide some server/cloud where we could upload it anyway. |
| nctnico:
--- Quote from: Performa01 on October 19, 2018, 06:51:11 pm ---How low do we need (or want) to go with such a measurement? For 10Hz, we'd need 10ms/div timebase and at least 10Mpts of data, which we could not handle over this forum. You'd need to provide some server/cloud where we could upload it anyway. --- End quote --- Wetransfer works excellent for sending big files to people. |
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