United States Patent [w]
 APICAL POSITION DETECTION APPARATUS
 Inventor: Masahiro Otsuka, Kawasaki, Japan
 Assignee: Toei Electric Co., Ltd., Kanagawa,
 Appl. No.: 09/190,829
 Filed: Nov. 12, 1998
 Foreign Application Priority Data
Aug. 24, 1998 [JP] Japan 10-237262
 Int. C I. A61C 19 04
 U.S. CI 433/72; 128/776
 Field of Search 433/72, 75, 27;
 References Cited
U.S. PATENT DOCUMENTS
5,017,134 5/1991 Saito et al 433/72
5,096,419 3/1992 Kobayashi et al. .
5,211,556 5/1993 Kobayashi et al. .
FOREIGN PATENT DOCUMENTS 4126753C2 ol 0000 Germany .
4139424C2 ol 0000 Germany . 19854223 5/1999 Germany .
Primary Examiner—Nicholas D. Lucchesi
Attorney, Agent, or Firm—Laff, Whitesel & Saret, Ltd.; J.
The present invention provides an apical position detection apparatus for accurately detecting the lact that a measuring electrode arrives at the apical position. The apparatus has a first current value measuring means for measuring a first frequency value by supplying a first frequency signal between the measuring electrode and the oral electrode, a second current value measuring means for measuring a second frequency value by supplying a second frequency signal between the measuring electrode and the oral electrode, arithmetic means for obtaining logarithmically converted calculation value by using a first measurement signal and a second measurement signal, and position signal formation means for obtaining an apical position detecting signal by addition or subtraction of the first measurement signal and the arithmetic value.
8 Claims, 8 Drawing Sheets