(19)

(11)

EP 0 592 660 A1

(12)

(43) Date of publication: 20.04.1994 Bulletin 1994/16 (21) Application number: 93911886.0 (22) Date of filing: 29.04.1993

(51) International Patent Classification (IPC):  G01F 3/ 08( . ) (86) International application number: PCT/GB1993/000891 (87) International publication number: WO 1993/022631 (11.11.1993 Gazette 1993/27)

(84) Designated Contracting States: AT BE CH DE DK ES FR GB GR IE IT LI LU MC NL PT SE (30) Priority: 29.04.1992 GB 19920009250 (71) Applicant: ABB KENT PLC Luton Bedfordshire LU1 3AE (GB)	(72) Inventors: BARROW, Mark, Sutherland 166 Grampian Way Luton Bedfordshire LU3 3HU (GB) ROGERS, Ivor, Thomas 58 Hazelwood Close Luton Bedfordshire LU2 8AR (GB) (74) Representative: Garratt, Peter Douglas  Mathys & Squire 100 Grays Inn Road London WC1X 8AL London WC1X 8AL (GB)