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New MicSig/EEVblog DP10007 HV Differential Probe

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EEVblog:

--- Quote from: BreakingOhmsLaw on March 29, 2021, 01:33:31 pm ---I have a DP10007 as well.

CMRR measured and (vs spec value) on 10x

50Hz   -70dB  (-80)
20kHz -55dB  (-60)
1MHz  -52dB (-50)
10MHz -33,2dB (-40)

No information how Micsig measures the CMRR though.
Can we agree on a common setup? Input leads twisted x-times, input signal etc.?

--- End quote ---

I'll shoot a video on this in a few day when I have time. MicSig are still looking into it.
My setup is a 50ohm terminator on the scope, 10MHz sine from the function gen as large as possible, measured and confirmed on one scope channel.
Leads of both inputs twisted reasonably tightly and both inputs shorted and connected across the 50 ohm load. Then using 20*Log (output p-p / Vgen p-p)
I use a HVP70 for comparison which is supposed to have indentical CMRR specs and the Micsig is way higher.
They say they are still working on it, but have not confirmed mt setup is correct or what setup they are using.

BreakingOhmsLaw:
Okay, repeated the measurement with what I think Dave meant:


Some remarks:
 - Scope is set to 20MHz Bandwith limit
 - V/div fine adjustment used to maximize amplitude in order to optimize ADC quantization.
 - Lead of DP10007 twisted 8x.
 - Measurements below 1MHz are difficult because the common mode signal is swamped in the noise. I used persistence and color grading and estimated the amplitude of the "cloud". 
 - The BNC splitters will introduce an error, ignoring that for now.

            x10    x100    Spec
50  Hz      -70    -56     -80
20 kHz      -50    -54     -60
 1 MHz      -49.5  -37.6   -50
10 MHz      -32.2  -20     -40

A final note: My DP10007 has a slight positive DC offset. Does anyone else see this?

mr.os:
I also made a measurement with my DP10007. I measured it with a HP 89410A and have so some graphs:

The green trace is the CMRR of the x10 range and the blue trace is the CMRR of the x100 range (the analyzer has done the math that the graphs are the direct CMRR). Some points (measured partially in another mode where I can't generate such a nice plot):
x10x10050Hz-82dB-79dB20kHz-59dB-57dB100kHz-56dB-57dB1MHz-50dB-42dB10MHz-37dB-22dB
So at least the x10 spec are in my measurements not so far away from the manufacturers spec. My probe is also relative new, maybe they have changed something.
My measurement setup:


Also checkd for DC offset and with shorted inputs the x10 range has around 360µV and the x100 range around 280µV. So this is fine.

mf_ibfeew:
>A final note: My DP10007 has a slight positive DC offset. Does anyone else see this?
I had a similar problem with my DP20003, more than 12V ofset (with the 200:1 range)
After complaint I got no new shiny probe, instead I got an email with the following instructions:
procedure for Micsig Auto-offset-calibration:
- connect probe to power (USB), switch on, short both input leads
- push down both range buttons simultaneous, after some time you will hear some relays clicking inside. The offset-error should be zero now
- switch off, switch on, test offset, be happy
- if my english is to bad: look at 
Maik

mrprecision:
Could anyone review my noisemeasurement?

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