We a planning to control a large laboratory setup by LV. It is a "really wet" chemical process, with a lot of water and also some highly active solvents around. It should be possible to quickly react to process changes and adjust some parameters by hand. We came to conclusion that mouse, keyboard, touchscreen are not suitable for the purpose, and that good old push buttons and rotary knobs are what we need.
We would set the initial parameters in the LV program using mouse/keyboard, thus we need to get only relative changes of the parameter from the rotary knob during the experiment. Thus a potentiometer looks like not the optimal thing for this job, whereas an incremental rotary encoder is exactly what we need. Such encoders cost just a couple of $€, e.g. # 623-4237 from RS Components.
I know how to interface a quadrature encoder to a counter. However we may need something like 5-7 knobs, and most NI DAQs have just one or two counters, and it looks like it's going to cost like 500$€ per channel, which is a bit expensive for the simple task. Specialized pulse counter DAQs by NI are in the PCI card form, which I'd like to avoid (and not exactly cheap, too). Are there any reasonable alternatives? The maximum expected pulse frequency would be below 100 Hz.
