| 摘要 |
1. A measuring arrangement for determining the concentration of dissolved organic substances in a liquid which also contains suspended solids, in particular sewage, comprising - a radiation source (S), radiating in the visible and ultra-violet spectral regions ; - a measuring vessel (5) which contains the test liquid (14) and has radiation-transmissive windows (6, 6a) arranged opposite to one another which delimit the measuring section in the path of rays from the radiation source (S) ; - first means for splitting the radiating into a visible and an ultra-violet radiation component ; - second means for detecting the radiation component after passage through the measuring path ; and - a circuit arrangement for the formation of quotients from the detector output signals, characterised in - that the first means has a filter device (8, 9, 10) which alternately allows the ultra-violet radiation component, namely the radiation of a first spectral region, which includes absorption bands of suspended solids and dissolved organic substances, and the visible radiation component, namely the radiation of a second spectral region, which only contains absorption bands of suspended solids, to enter the measuring path ; - that, in order to shorten the effective optical path length (I1 ) in the test liquid, a radiation-transmissive displacement body (4) can be periodically inserted into the measuring path for the duration of at least one filter alternation cycle ; - that the second means has a non-selective radiation detector (D) which is arranged after the outlet window (6a) of the measuring path ; - and that the evaluation circuit consists of an evaluation circuit (13) which is fed by the radiation detector (D) and in which the proportion of dissolved organic substances in the test liquid is calculated from the four detector output signals which result as functions in the two different spectral regions with two different optical path lengths (11 , 12 ), and is indicated. |
