Apparatus for measuring the muzzle velocity of a projectile

Claim 2

Apparatus for measuring the muzzle velocity of a projectile comprising a gun barrel, a measuring system at the muzzle of said gun barrel having two relatively spaced coils through which the projectile passes for inducing two signal pulses, bars on which said coils are mounted, said bars changing their length with a variation of temperature, means for measuring the time interval between said induced signal pulses, a temperature sensing element on said measuring system and means utilizing the output of said sensing element to vary the measured time interval.

Claim 3

Apparatus according to claim 1 wherein said sensing element comprises a temperature-dependent resistor, a phase-inverting stage, a modified monostable multivibrator, two AND-gates, an OR-gate, a bistable multivibrator and a monostable multivibrator, said signal pulses being applied to said phase-inverting stage and the output of said phase-inverting stage being connected to the input of said modified monostable multivibrator, said temperature-dependent resistor producing a compensating voltage which is applied to said modified monostable multivibrator for varying the time the modified monostable multivibrator remains in its quasi-stable state, the input and the output of said modified monostable multivibrator being each connected to one of the inputs of said AND-gates, the other inputs of said AND-gates being connected to the two outputs of said bistable multivibrator, the outputs of the two AND-gates are taken through said OR-gate to the input of said monostable multivibrator, which delivers the corrected signal pulses in its output and which corrected signal pulses are fed back to the symmetrical inputs of the bistable multivibrator.

Claim 4

Apparatus according to claim 2, wherein said modified monostable multivibrator comprises a first and a second transistor, said first transistor being normally in the conductive state, said first transistor having a base connected to a constant current supply and said second transistor being normally non-conducting, said second transistor having the collector applied to the compensating voltage.

Claim 5

Apparatus according to claim 2 comprising an operational amplifier, wherein said temperature-dependent resistor is included in the input circuiT of said operational amplifier, wherein the feedback circuit of said operational amplifier contains a non-linear relationship existing between the spacing of the coils of the measuring system and the change in temperature, and wherein the output of said operational amplifier is connected to the collector of said second transistor.