Patent ID: 6064196
Filing Date: 2000-05-16
Classification: G01P

Abstract:
Apparatus for measuring the muzzle velocity of a projectile, comprising:a washer-shaped magnet having a north pole and a south pole that is positioned on a projectile body so that its outside diameter is located close to that of the projectile's outside diameter, and the south pole of said magnet faces the direction in which the projectile will exit the muzzle;a position sensor having a first and a second inductive coil mounted a known separation apart, wherein a voltage is induced in each coil when said magnet passes through said inductive coil;a first and a second wide bandwidth preamplifier, each having an input and an output;first and a second comparator pairs, each comparator in said comparator pairs having a positive input, a negative input connected to and electrically coupled to ground voltage, and an output;a digital counter having a start input, a stop input, an in input, a reset input and an output; anda high precision frequency source connected to and electrically coupled to the input of said digital counter to provide a clock signal to said digital counter;wherein the input of said first wide bandwidth preamplifier is connected to and electrically coupled to said first inductive pickup coil to amplify the voltage induced in said first inductive coil when said magnet passes through it and the input of said second wide bandwidth preamplifier is connected to and electrically coupled to said second inductive coil to amplify the voltage induced in said second coil when said magnet passes through it;wherein the positive inputs of said first comparator pair are connected to and electrically coupled to the output of said first wide bandwidth preamplifier and the positive inputs of said second comparator pair are connected to and electrically coupled to the output of said second wide bandwidth preamplifier;wherein the outputs of said first comparator pair are connected to and electrically coupled to the start input of said digital counter to start said counter when the voltage induced in said first inductive coil crosses zero; andwherein the outputs of said second comparator pair are connected to and electrically coupled to the stop input of said digital counter to stop said counter when the voltage induced in said second coil crosses zero, and thereby generate a velocity count signal, corresponding to the velocity of the projectile, on said output of said digital counter.