You wrote, "I find it hard to believe that so many instrument did not really meet the spec...".
I think you ascribe too much computing intelligence to these instruments. Many of these devices run a simple "homemade" operating system, or better, a commercial single-threaded embedded operating system. I'd bet most devices have a single microcontroller that is monitoring I/O, command processing, front panel processing, and taking the measurements. And the code to handle all that wants to handle just one thing at a time. For example, if an instrument is taking a measurement, and you're sending it the next command, a lot of instruments abort the measurement because it thinks you have something new and important to say. Part of the beauty of virtual instrumentation is that you have a real operating system at your disposal, and a lot of different things can be going on in the computer at the same time without interference. Brian
