(19)

(11)

EP 0 257 054 A1

(12)

(43) Date of publication: 02.03.1988 Bulletin 1988/09 (21) Application number: 87901088.0 (22) Date of filing: 04.02.1987

(51) International Patent Classification (IPC):  G01L 7/ 08( . ) G01L 11/ 00( . ) (86) International application number: PCT/GB1987/000079 (87) International publication number: WO 1987/004789 (13.08.1987 Gazette 1987/18)

(84) Designated Contracting States: AT BE CH DE FR GB IT LI LU NL SE (30) Priority: 07.02.1986 GB 19860003078 (71) Applicant: SEETRU LIMITED Hanover Place Bristol BS1 6UT (GB)	(72) Inventors: VARGA, Otto, Herman Bradford-on-Avon Wiltshire (GB) GODDARD, Robert, William Bristol BS8 4QG (GB)