Fri 26 May 2006
Sometimes it is necessary to probe two sides of a single PCB with multiple probes while keeping your hands free to turn some knobs. This can be accomplished by using expensive PCB vices with specialized probes, or you can make your own using some optical breadboard equipment and old micromanipulators. I put this one together by using some spare Thorlabs parts that were lying around the lab and some electrode micromanipulators from the early 80s.
The unit under test here is a digitally-controlled, 12 channel amplifier. The gain and offset for each channel is programmed using an x9250ts24 quad pot from Intersil. Since the whole board interfaces a National Instruments PCI-6229 board, I used the digital I/O on that board to program the pots. What is strange is that some of the pots refuse to set the gain properly, something like a misalignment in the SIO/SCLK waveforms. Unfortunately, I have a slightly different board in the lab setup as compared to the acquisition setups, and the system is less heavily loaded, so after all of this work, I am unable to reproduce the bug. Maybe I will come up with a good way to abuse the computer to try to corrupt the digital waveforms over dinner.
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