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All about Keithley DMM7510. Bugs and features, recipes, advice, notes.
Kleinstein:
The quite limited frequency response in the 100 V and 1000 V ranges is a bit disappointing. Especially the low cut of for 100 V is odd, as there is the same divider and just the amplifier in x 10 mode instead of x 1. This corresponds to the 1 V and 10 V ranges, that seem to be fine to much higher frequency.
For 1 MSPS sampling the Nyquist limit is at 500 kHz - so there should be large drop in this range. If looking at more than just the pure RMS or peak to peak values, there should be signs of aliasing. So how does the waveform look for something like a 550 kHz signal, when measured at 1 MSPS.
It looks like there is no anti aliasing filter, not even a fixed one (e.g. 400 kHz) for 1 MSPS sampling.
MegaVolt:
--- Quote from: Kleinstein on September 27, 2019, 07:54:02 am ---The quite limited frequency response in the 100 V and 1000 V ranges is a bit disappointing. Especially the low cut of for 100 V is odd, as there is the same divider and just the amplifier in x 10 mode instead of x 1. This corresponds to the 1 V and 10 V ranges, that seem to be fine to much higher frequency.
--- End quote ---
If you look at the noise in the specification, then the 100V range has a higher noise level. Is the band reduced to reduce noise?
--- Quote ---For 1 MSPS sampling the Nyquist limit is at 500 kHz - so there should be large drop in this range. If looking at more than just the pure RMS or peak to peak values, there should be signs of aliasing. So how does the waveform look for something like a 550 kHz signal, when measured at 1 MSPS.
--- End quote ---
Yes, all crossings across the Nyquist border have a drop. This is clearly visible if you change the frequency linearly and not in steps.
And all that is higher than the Nyquist frequency is spectrum overlay. The ADC has a very good sample/hold device with sampling times of the order of 100 ns.
--- Quote ---It looks like there is no anti aliasing filter, not even a fixed one (e.g. 400 kHz) for 1 MSPS sampling.
--- End quote ---
Unfortunately it is so. As Bred said, the user must make an external good filter himself if he wants to watch the signal in a limited band. If this is not done, then all the noise from the Nyquist frequency to the MHz pair will fall into the signal :(((
MegaVolt:
Updated the header:
Added by:
- improvements to the new firmware;
- added new bugs and features;
MegaVolt:
The new screen of death.
The device after it did not react to anything. I had to reboot. Unfortunately, I can’t say how to repeat it. I switched between DCV and Digi V modes, used a large buffer and played with the Count parameter.
MegaVolt:
--- Quote from: E-Design on November 23, 2019, 02:29:33 am ---Yes the 100V and 1kV ranges have bandwidth limited by the huge 10Meg divider. Internal changes when going from 100V and 1kV can make those differ a bit as well. The divider wasn't AC balanced because most of the user base doesn't do high voltage at high frequency generally.
--- End quote ---
The 100V range behaves very strangely.
For example, I see a reaction from a change in input resistance.
At 10 MΩ - 750 μV
At Auto - 65 uV
At the same time (Auto) it can be seen that emissions appear on the noise track :(
Is there any difference between 10 MΩ and Auto?
If you select a range of 1000V there is no such effect.
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