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EEVblog 1415 - Reverse Engineering the DP10007 Differential Probe

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EEVblog:
Reverse engineering the Micsig DP10007 high voltage differential probe.
Turning the PCB into a schematic.



Reverse enginering how-to for the Rigol oscilloscope:
DIY light box for PCB photography:

BrianHG:
     Old fashioned 'Paint Shop Pro' allows adding multiple graphics layers and geometry layers for text and arrows which you can adjust the transparency between them and their layer order and layer-layer alignment on the fly.  In fact, I would use and still use today my old Paint Shot Pro 6 from the year 2000 to do exactly what you want.  It also has the edge outline filters if you want such image processing.

     Also, if you have equal spacers at the 4 corners of the pcb, some flatbed scanners will generate a perfectly square edge-edge accurate image even though the spacers lift the PCB off of the glass so that the components don't sit in a bumpy random height from the flatbed scanner.

voltsandjolts:
Regarding the relay, using a latching type avoids thermal emfs on the contacts generated by the heat from a continuously powered coil.
Although, being post-amplifier here the signal levels aren't tiny....ah, but that amp is unity gain of course.

Regarding the SMD input dividers, board cleanliness is going to be critical to get any flux out from under those components.
SMD is obviously good for automated assembly, so I might have used larger parts with slots underneath for more effective cleaning.

tszaboo:
There aren't too many things in this differential probe. Still probably a bunch could be shaved off from the BOM, if we throw out the digital part, replace it with a slider switch and two comparators. Not that it matters probably, as most of the cost is the injection moulds/distribution.
I wonder how hard can be to make a DIY version of it.

floobydust:
I reverse-engineered a Pintek DP15K-Q high-voltage differential probe. Specs 15kVp-p 35MHz Input impedance 30MEG (I think), x100, x1000.
Pintek is an OEM you might want to take a look at Dave.

The circuit is your usual instrumentation three op-amps config with AC and DC CMRR adjust, relay for x100 atten, DC-DC converter to make +/-12VDC with 6-12V in (typ. 9V), a DC servo for offset.
I didn't get all the circuit, the numbers were sorta sanded off IC's and traces running around under things. Input op-amps THS4631D, TL062? for servo, THS3091 for the diff amp - all the same circuit as many others. No MCU.

Making one of these would be a good kit. I couldn't believe the markup on American private label versions of the same product. What a cash cow. It's just too expensive for what it is then.

edit: added pics of the HV front-end, it's just two 10kV rated resistors and comp caps likely rated as not as much  :P  The probe is rated 15kVp-p differential and 5.5kV RMS common-mode Cat. II/Cat.III

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