Abstract: Analytical apparatus includes a pyroelectric or other thermo-electric transducer element (10) in strip form. Thin film electrodes (12,14) are provided and one or more dots of reagent (16) are deposited on the transducer surface. A small amount of biological or other sample is deposited over the reagent dots which undergo selective colorimetric changes. The transducer is illuminated from below by LED light sources (24) and light absorption in the reagent regions is detected as microscopic heating at the transducer surface. The electrical signal output from the pyroelectric transducer is processed to derive analyte information.