open dvm as an open frame

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I just discovering your open dvm project.Great idee !!!
I think that projet as a frame  :
a display (a led, several lines of 7 segments or a unic big graphic LCD ),
 a keyboard (4 buttons for exemple)
and several plugins slots.Theses slots could be locked with screws (safety reason ).For exemple, you can have an unique voltmeter slot, at the early begining...
Dont get glued with an unic CPU .Dont get glued with a fix resolution or sample rate.Use a standard very efficient open programing language ( I would choose FORTH , witch is  very compact (2kbyte) ).
So, the same frame should be extendable without any limitation.The same frame for the hand dvm 3.5digit and the very powerful 1ppm bench dvm and possilbly for the open oscilloscope, the open , the open 64 thermocoupler thermometer, signal generator...!
No limitation for the screen resolution, the number off button, the number of slot...
Sise can be an very big problem for an pocket dvm but not for an bench dvm.So you  can start with a bench dvm ( 0.1% accuracy 4.5 digits for exemple).
The slot connector :
I would use a small transformer (2 or 3 pins for +5V or +/-5V),
 2 opto couplers (signal in, signal out) or more (I2C, SPI, ?).It would be nice to use ADC as ltc2400 (24 bits sigma delta less than 10$, ideal for a bench dvm !).I/O pin in a I2C or SPI IC could be used for auto range etc...