An interface to input analogue signals to a digital computer.

An electrical control unit is described which permits analogue signals from most sources to be made compatible with, and optimise the use of, an A/D converter. This circuitry enables the signal to be offset, relative to the electrical zero, and to be reset to zero using a push button. Extension of this unit has enabled mechanical movement, such as rotation of a shaft, to be measured. In order to make the most efficient use of the A/D converter the gain of the output can be varied.