(19)

(11)

EP 0 581 896 A1

(12)

(43) Date of publication: 09.02.1994 Bulletin 1994/06 (21) Application number: 92913613.0 (22) Date of filing: 23.04.1992

(51) International Patent Classification (IPC):  G01F 1/ 68( . ) G01F 5/ 00( . ) G01F 1/ 684( . ) G01F 25/ 00( . ) (86) International application number: PCT/US1992/003341 (87) International publication number: WO 1992/020006 (12.11.1992 Gazette 1992/28)

(84) Designated Contracting States: AT BE CH DE DK ES FR GB GR IT LI LU MC NL SE (30) Priority: 26.04.1991 US 19910692181 (71) Applicant: UNIT INSTRUMENTS, INC. Yorba Linda, CA 92687 (US)	(72) Inventors: DOYLE, Michael, John Villa Park, CA 92667 (US) VU, Kim, Ngoc Yorba Linda, CA 92686 (US) VAVRA, Randall, James Orange, CA 92667 (US) LEMAY, Dan, Brown Palos Verdes Estates, CA 90274 (US) (74) Representative: Cross, Rupert Edward Blount, et al  BOULT, WADE & TENNANT 27 Furnival Street London EC4A 1PQ London EC4A 1PQ (GB)