| 摘要 |
PROBLEM TO BE SOLVED: To surely judge the position of a shutter without operating the shutter by providing a control circuit generating a current command to a driving circuit, a current amplifying outputting circuit amplifying the output of the control circuit, and a measuring circuit measuring the self-inductance variation of a detecting coil. SOLUTION: At the time of confirming the position of the shutter 2, the control circuit 81 outputs a fixed current command to the current amplifier 82 to make a driving current Id flow through an energizing coil 62 to superpose magnetic fluxesϕA,ϕB generated by permanent magnets 5A and 5B and a magnetic fluxϕC generated by the coil 62. Then at the time of making the driving current Id flow through the coil 62, an operating point in an area S moves and by setting the driving current to be proper, the area S is made a saturated area and a non-saturated area. Then, the area S is also the magnetic circuit of a detecting coil 7, the self-inductance of the coil 7 can be measured by a self-inductance measuring circuit 83 to judge the position of the shutter 2.
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