This paper described a two-channel

APPLE II Compatible

12 bit data acquisition system. The analog input section contains two S/H amplifers

simultaneous signals may be acquired. This system is used as the data processor of measurement instruments to provide the instantaneous computed function. This system connectting with the lock-in analyzer is especially suitable for the orthogonal vector calculation

√

A

2

+B

2

and other both simulteneous signals processing. For example

the typical applications in double beam spectroscopy

A±B

A×B

A/B

Lg (A/B). Here

we discussed the composition of this system

and how to feed 12 bit data into the memory by the action of the APPLE II bus signals. The flow-chart of programming was given out.