/diy/ - Do It Yourself

>>2039080
the ref pin is "just" another input to the in amp, but one that isn't multiplied by the amp's set gain. what you're describing is like the offset-null pins of early op amps, back before laser trimming was cheap and easy

>>2039081
you will need a hell of a power supply
just 1 Form C? that sounds rough. some 2 Form C contact units would help with RAM and math and multiplexing
so at bare minimum you'd need 30 nybbles for 10 digits each of result, input accumulator, and one scratchpad (mul/div), and a handful of small scratchpad registers and counter registers which you'd have to get a bit further into the design to quantify
>DIP switches for ROM
better: plug diodes into a matrix of pin sockets. you'll need the diodes on the switches anyway to keep 1-bits from backfeeding through other switches. diodes will be happier at lower current therefore higher voltage is preferred
I would try to make certain tasks as hardware-driven as possible, and reserve the program store for cycling through the big number arrays, normalizing results, etc. maybe the entire process of inputting a stream of digits into a storage register could be handled without CPU intervention. halt-until-event processor instructions were pretty common in mechanical calculators as an implementation technique, in discrete CPUs on mainframes and minicomputers as a cost-saving and virtualization-assisting measure, and in portable devices today as a power-saving measure. the whole project would look less like the sort of general-purpose processor we're used to, but it would be a lot quieter at idle

>>2039140
you need a cookbook. look up "op amp cookbook" and you'll find a Nuts & Volts article series, a book published by Sams, and a TI app note, among many others. then go to the roll page in the OP and get an application to assemble them in

>>2039171
it's so the internals of the inamp don't distort the intended ref voltage

>>2039172
I meant the high end OF UNI-T, ~equivalent to mid-low Fluke