Helpful hardware ideas

We present some hardware features which we have found to be very helpful. You might want to incorporate some or all of these ideas (or none, possibly) into a homebuilt spectrometer or you may wish to specify these features in commercial spectrometers. 

The first feature is a display of the current number of scans in real time. We find it very convenient to have the current number of scans showing at all times. This is especially true for a series of fairly short accumulations of the order of half an hour because misestimating the duration of the run by a few minutes wastes a significant fraction of the total time. Without a counter readout, you either have to interrogate the computer (thus interrupting the data taking process) or just wait around for the accumulation to finish. 

This is an easy feature to implement. You need a display device (like LED s with decoders included) and a latch which will remember what the number is. The computer will output the updated count each cycle to the latch. 

A second useful feature is a set of analog inputs into the computer from knobs. The knob readings are digitized 

The construction of such circuits is also quite easy. The knobs operate variable resistors which feed variable voltages into a multiplexed ADC. The latter should have a latched output, i.e., it should put out the last value converted until the new conversion. The speed of the ADC is not critical and you can use an inexpensive one. 

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