Communications. Variable gain integrator for photomultiplier read-out

Abstract

The variable gain integrator integrates the current from a photomultiplier (PMT). The integrator is built around an Intel 82C54 chip. The PMT current is converted into a frequency which is fed to the input clocks of the timer. An interface using two bidirectional 8-bit ports on an 8086 microprocessor gives full control of the timer. The three counters in the timer are ganged together and have a high and low entry point. When very low currents are measured on-board circuitry automatically detects and amplifies the current and feeds it to a lower counter. This interface also allows the input signal to be gated.