We have developed a device which employs parallel dc electric and magnetic fields in combination with an array of collectors and accompanying electronic circuits to measure simultaneously the momentum distributions of different ion species from a laser produced plasma. This diagnostic system automatically separates the ion species according to mass to charge ratio and utilizes the cyclotron motion to provide the momentum separation. The principle of operation, design configuration, and circuitry for the system are presented along with representative data obtained from a series of laser-induced plasma experiments.