An assembly for determining an analyte concentration in a fluid sample, comprising: a test sensor comprising a fluid-receiving area for receiving a fluid sample, the fluid-receiving area containing a reagent that produces a measurable reaction with an analyte in the sample, the test sensor having a test-sensor temperature and the reagent having a reagent temperature; and a meter comprising: an opening configured to receive the test sensor; a measurement system configured to determine a measurement of the reaction between the reagent and the analyte; and a temperature-measuring system configured to determine a measurement of the test-sensor temperature when the test sensor is received into the opening,, wherein the meter determines a concentration of the analyte in the sample using the measurement of the reaction and the measurement of the test-sensor temperature, characterized in that: the test sensor has a grating disposed along a surface of the test sensor, the grating including a series of parallel linear structures equally separated by a distance that changes in response to temperature, and the temperature-measuring system includes a light source and a light detector, the light source being configured to direct incident light to the grating, and the detector being configured to receive, from the grating, diffracted light that changes according to changes in the distance separating the linear structures of the grating, the temperature-measuring system determining the measurement of the test-sensor temperature according to the diffracted light. a test sensor comprising a fluid-receiving area for receiving a fluid sample, the fluid-receiving area containing a reagent that produces a measurable reaction with an analyte in the sample, the test sensor having a test-sensor temperature and the reagent having a reagent temperature; and a meter comprising: an opening configured to receive the test sensor; a measurement system configured to determine a measurement of the reaction between the reagent and the analyte; and a temperature-measuring system configured to determine a measurement of the test-sensor temperature when the test sensor is received into the opening,, an opening configured to receive the test sensor; a measurement system configured to determine a measurement of the reaction between the reagent and the analyte; and a temperature-measuring system configured to determine a measurement of the test-sensor temperature when the test sensor is received into the opening,, wherein the meter determines a concentration of the analyte in the sample using the measurement of the reaction and the measurement of the test-sensor temperature, the test sensor has a grating disposed along a surface of the test sensor, the grating including a series of parallel linear structures equally separated by a distance that changes in response to temperature, and the temperature-measuring system includes a light source and a light detector, the light source being configured to direct incident light to the grating, and the detector being configured to receive, from the grating, diffracted light that changes according to changes in the distance separating the linear structures of the grating, the temperature-measuring system determining the measurement of the test-sensor temperature according to the diffracted light.