A Miniaturized Turn-Counting Sensor Using Geomagnetism for Detecting Flight Range of Ammunition

This paper presents a miniaturized turn-counting sensor (mu-TCS), where geomagnetism and high-rpm rotation of ammunition fired by a rifled gun are used to detect the turn number of the ammunition based on Faraday´s law. The mu-TCS, composed of a coil and Co-based amorphous cores, is designed to effectively decrease the range error of small-caliber ammunition. The robust structure with no moving part makes it possible for mu-TCS to survive in a gunfire environment of ~30,000 g´s. The mu-TCS has been designed on the basis of the simulation results of Maxwell^reg 3D. In the experimental studies: static mu-TCS test using a solenoid-coil apparatus and dynamic mu-TCS test (firing test), the fabricated mu-TCS has shown that an induction voltage of 6.5 mV_p-p is generated at a magnetic flux density of 0.05 mT and a rotational velocity of 30,000 rpm, achieving a SNR of 44.0 dB, a nonlinearity of 0.59% and a frequency-normalized sensitivity of 0.26plusmn0.01 V/T-Hz in a temperature range of -30 to +43degC. Firing test has verified the shock survivability of the mu-TCS in a high-g environment.