| 摘要 |
Before the measuring stage, there is a calibration stage in which the light intensity is controlled so the light detected by the photosensitive detector gives an output signal (Uc) equal to a reference signal (Up). An Independent claim is also included for an apparatus for the above process including a supply module (6), a light source (4), a photosensitive detector (5), a comparison module (7) or measuring module (8) and a display (9). Preferred Features: One or more specific reactants (2) is/are introduced in solution into a reservoir (3) containing a set dose of the sample which color the sample as a function of its concentration. The sample is then illuminated with a light source (4) and the light passing through the sample is measured using a photosensitive detector (5). The reference signal is calculated as a function of the coloration by the reactants and the response curve of the detector. The light source is supplied with current by a controlled source. The comparison module includes a chain of resistances R'0 to R'n between which are nodes U'0 to U'n. One end of the chain carries the detector and the other end an internal resistance Rp for the reference signal. It also includes comparators C'0 to C'n allowing the value at each node to be compared to Ug, the set voltage for the sample. The display is a series of electroluminescent diodes D'0 to D'n each of which lights up when the concentration threshold it represents is passed. It also includes logic circuits which only allow the diode corresponding to the last threshold passed to light up. The measuring device comprises a voltage bridge ABCDEF with two branches ABF and CDF, extended by a branch FG. The ABF branch carries the detector, a node B and a resistance Ri in series, and the CDF branch carries the reference value Rp, a node D and a resistance Ri in series. The BD branch carries a potentiometer P3 with a variable node E and the display module includes a branched voltage or amp display which is in parallel with B and E or in series with P3 depending on whether it is measuring voltage or intensity. The measuring module also includes a variable resistance Rv on the FG branch, which can increase or decrease the amplitude of values between B and D and which can make the display device coincide with the concentration unit. A selector button on the measuring device allows a variable resistance Rv to be selected simultaneously with an internal resistance Rp for the reference value and a potentiometer P1 controlling the intensity of the light source, to allow selection of a particular type of measurement. There is a light source in series with each potentiometer P1. |
