LONG-PULSE ANALOG INTEGRATION

The presence of variable offsets at the input stage of analog integrators produces drifts in the output which limit the duration for which integration can be carried out at specified accuracy. In this article an integration system is demonstrated, accurate to within a few millivoltseconds over a time scale of several hours, with no special temperature control of the environment. The principle is to alternate between two individual integrators. While one integrates the signal, the other performs a drift measurement. This provides information sufficient to construct a continuous integral, and to perform time-dependent drift compensation. Estimates are given to show that the scheme could meet the magnetic diagnostic requirements of the next generation long-pulse devices for the magnetic confinement of thermonuclear plasmas. Modifications to the system tested are suggested, which could significantly further extend the period of accurate integration.