| 摘要 |
PROBLEM TO BE SOLVED: To provide a length measuring device capable of performing highly accurate length measurement with a simple constitution. SOLUTION: Each pair of a first detection part 242 and a second detection part 243 is provided at unchangeable intervals with a support 241 made of a low expansion material on one end of a low-expansion magnetostrictive delay line 210 having a magnetostrictive characteristic. A pulse current is supplied into the magnetostrictive delay line 210 by a pulse current generation means 220, to thereby generate an ultrasonic wave by an ultrasonic wave generation magnetic body 230 provided integrally on a movable body. Voltage pulses are generated respectively at the first detection part 242 and the second detection part 243 by the ultrasonic wave propagating in the magnetostrictive delay line 210. Propagation times from supply of the pulse current to generation of the voltage pulses are operated respectively by performing time integration at an integration part, and the distance from the ultrasonic wave generation magnetic body 230 to the first detection part 242 is operated by a calculation part 330 based on the distance between the first detection part 242 and the second detection part 243. COPYRIGHT: (C)2004,JPO&NCIPI
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