TI has two high speed (2MSPS) 16 bit analog to digital converters (ADCs), the ADS8411 and ADS8412. One is differential, the other is single ended.
A PIC 18F2550 (with USB) can read the ADC and send data to a PC for display.
2 MHZ of speed isn't that great, but its faster than a multimeter :)
USB full speed is 12 Mbps
I guess I can sustain about 8Mbps of data through the USB, leaving 4 bits of control layer for every 8 bits of data.
At full ADC speed (2MSPS) samples would have to be limited to 4 bits resolution (and combined into a single byte?) to hit the 8Mpbs mark.
8 bit resolution = 1 million samples/s max (8mbps)
16 bit resolution = 500K SPS max (@ 8 mpbs throughput)
The ADS841x interfaces with some control lines and a 16 bit bus - a low instruction count can be used to move the value from the PORTS to the USB peripheral.
@ 48MHZ the pic does 12 million instructions/s.
@ 2 MSPS (or 2 MHZ acquisition speed, 4 bits resolution) there is a 6 instruction limit to move data from port to USB. This could be considered 12 instructions @ 4 bits because 6 instructions would just move 4 bits into a byte, other operations could be done during this time.