Photometric reading device

A photometric reading device comprises a plurality of reading elements (30), each comprising a light emitting diode and a corresponding photodiode on opposing sides of a sample pathway along which a sample microplate (l0) can travel. The microplate (l0) includes rows of sample wells arranged transverse to the line of relative motion of the microplate (l0) and the reading elements (30). The reading elements (30) are arranged such that, during continuous relative motion of the reading elements (30) and the microplate (l0), the reading elements (30) come into registration sequentially with the wells in the first row of wells in the microplate (l0), then with the wells in the second row of wells, and so on.