Patent GB-1485506-A (GB)
Title: System for detecting the particular chemical composition of a fluid
IPC: G01N35/00
Filed: 1974-07-31
Abstract: 1485506 Photo-electric measurement of chemical tests OLYMPUS OPTICAL CO Ltd 31 July 1974 [31 July 1973(11) 12 Dec 1973 20 June 1974(2)] 32643/74 Heading G1A [Also in Division B8] In a system for analyzing a fluid in which a test piece carrying a plurality of reagents 11 is reacted with the fluid and the colour changes in the reagents are measured, the colour changes are measured photo-electrically and the results printed. The system can identify the test piece and hence the tests being carried out and can compare the results with stored values so that results can be printed out in the correct units. The test piece comprises a transparent substrate along which the different reagents are spaced (1 la- 11d) not all the positions necessarily being occupied. The extent of reaction is read by reflection of the signal from source 21a to detector 12e via light guides 12c, 12d, a filter preferably being interposed between 12d and 12e. A reference reflection piece is preferably placed at one end of the test piece and activates alarm circuitry when the measuring system output falls below a predetermined value. The test piece is identified by detector 13a which detects light transmitted through the substrate between the test pieces. The presence/ absence code resulting from relative movement between the test piece and the detector/source combination gives a digital signal representing the test piece.  The output of measuring detector 12e is converted at 14 to a frequency significant pulse train  which is fed to operation unit 15 comprising counting circuits in which the output is digitized. The output from detector 13a is converted at 13 to a digital code representing the type of test piece and the code selects the correct comparison data from memory 18. Comparator 16 compares the reference and test date and feeds the value to printer 19 along with details of the test. In an alternative embodiment all samples may be read together; a detector 497 and filter 496 being associated with each respective portion 492 of an enlarged measuring head 491. Illumination is from a single source 498. The test pieces may be supplied from a sealed container 460 in which they are stacked. Each piece is transferred to test fluid bath 483 for a predetermined time and then test piece 11 and measuring head 491 are moved away from the bath, upper position Fig. 44, while the measurement is performed. The test pieces may also be supplied from a single elongated strip, the pieces being cut off at the required positions. Preferably the pieces are covered with a protective film which is removed before measurement. Alternatively the test pieces may be cut transversely from a roll which comprises longitudinally extending strips of reagent. When the reaction times between test fluid and the different reagents differ, a dropping pipette and suitable control circuitry are supplied for soaking each reagent with test fluid at the correct time before measurement. The test piece is preferably moved intermittently past the reading head by a stepped cam which also carries index marks to assist in test piece identification and to ensure that the test piece is stationary during measurement.