An arbitrary-waveform generator for tuning spectrometers

A microprocessor-based arbitrary-waveform generator has been designed and constructed to provide synchronised tuning for scientific instruments during collection of data. The instrument utilises a piecewise quadratic algorithm to interpolate the required values on the generated curves. It replaces existing techniques, which typically offer a range of analytical solutions to the problem, each of which is essentially inappropriate for the application. The new instrument can simultaneously provide four independent output curves, of arbitrary shape, each containing up to 4096 points having 8-bit resolution. Scanning rates as high as 1 ms per data point can be used. The instrument has been tested using electron energy-loss and photoelectron spectrometers and it is reported to satisfy requirements. The prototype has been used in a photoelectron study of molecular oxygen and has enabled improved results to be obtained.