Test sensor with grating for determining the temperature of the sensor

An assembly determines an analyte concentration in a sample of body fluid. The assembly includes a test sensor (100) having a fluid-receiving area (110) for receiving a sample of body fluid, where the fluid-receiving area (110) contains a reagent (115) that produces a measurable reaction with an analyte in the sample. The assembly also includes a meter (200) having a port or opening (210) configured to receive the test sensor (100) ; a measurement system (220) configured to determine a measurement of the reaction between the reagent and the analyte; and a temperature-measuring system (250) configured to determine a measurement of the test sensor (100) temperature when the test sensor (100) is received into the opening (210). The meter (200) determines a concentration of the analyte in the sample according to the measurement of the reaction and the measurement of the test sensor temperature.