Morgan R J, Karnowka T P, Solie T N
Biomed Sci Instrum. 1989;25:261-5.
The Macintosh II has the hardware to make a good scientific data acquisition and data processing machine. The data acquisition boards currently available do not sample multiple channels simultaneously. They are also relatively slow. We have designed a fast Analog-to-Digital Board for the Macintosh II that samples eight channels at once. This board acquires data with sampling periods from 1 microsecond to 1.6777215 seconds in increments of 100 nanoseconds. Any jitter is due to the stability of the clock which is about one part per billion. The actual analog-to-digital conversion time is 500 nanoseconds with another 500 nanoseconds taken up by the track-and-hold amplifier acquisition time and the multiplexer setting time. The board samples as many as eight channels, giving 12-bit resolution for signals between plus and minus 2.5 volts. For eight channels the maximum Nyquist frequency is 62.5 KHz. The board will acquire single-channel data that has frequencies up to 500 KHz. Simultaneous comparisons of two channels can be made for signals that have a highest frequency component of 250 KHz. Thirty-eight integrated circuits were used on a single-slot board that connects to the Macintosh II's 32-bit NuBus.
麦金塔II型计算机具备成为一台出色的科学数据采集与数据处理机器的硬件条件。目前市面上的数据采集板无法同时对多个通道进行采样。而且它们相对较慢。我们为麦金塔II型计算机设计了一款快速模数转换板，它能一次对八个通道进行采样。这块板以1微秒至1.6777215秒的采样周期采集数据，增量为100纳秒。任何抖动都归因于时钟的稳定性，其约为十亿分之一。实际的模数转换时间为500纳秒，另外500纳秒用于采样保持放大器的采集时间和多路复用器的设置时间。该板可对多达八个通道进行采样，对于正负2.5伏之间的信号提供12位分辨率。对于八个通道，最大奈奎斯特频率为62.5千赫。该板将采集频率高达500千赫的单通道数据。对于最高频率分量为250千赫的信号，可对两个通道进行同步比较。在一块连接到麦金塔II型计算机32位NuBus的单插槽板上使用了38个集成电路。
