A device for analysing a polymerase chain reaction in a fluid sample, the device comprising: a current source configured to cause the polymerase chain reaction by heating the fluid sample within a target zone; a camera imaging device configured to record a plurality of images of the fluid sample in the target zone while the current source causes the polymerase chain reaction; and a controller configured to, for at least one of the plurality of images, (i) virtually divide the target zone in the respective image into a plurality of bins without the bins being separated by physical barriers, (ii) distinguish wanted objects in the plurality of bins from an unwanted object in the plurality of bins by comparing a size or shape of objects in the respective image to an average size or an average shape of blood cells, and (iii) determine whether the fluid sample tests positive or negative for a bacteria or virus based on the wanted objects by selecting at least two of the plurality of bins that overlap a cluster of wanted objects and calculating a mean fluorescence value of the at least two of the plurality of bins, wherein the wanted objects include cells, and the unwanted object includes an object that does not have at least one of the average size or the average shape of the cells, and wherein the controller is configured to at least one of (a) exclude at least one of the plurality of bins from the mean fluorescence value calculation if the at least one of the plurality of bins overlaps the unwanted object, or (b) assign a weight to at least one of the plurality of bins used in the mean fluorescence value calculation based on the proximity of the at least one of the plurality of bins to the unwanted object. a current source configured to cause the polymerase chain reaction by heating the fluid sample within a target zone; a camera imaging device configured to record a plurality of images of the fluid sample in the target zone while the current source causes the polymerase chain reaction; and a controller configured to, for at least one of the plurality of images, (i) virtually divide the target zone in the respective image into a plurality of bins without the bins being separated by physical barriers, (ii) distinguish wanted objects in the plurality of bins from an unwanted object in the plurality of bins by comparing a size or shape of objects in the respective image to an average size or an average shape of blood cells, and (iii) determine whether the fluid sample tests positive or negative for a bacteria or virus based on the wanted objects by selecting at least two of the plurality of bins that overlap a cluster of wanted objects and calculating a mean fluorescence value of the at least two of the plurality of bins, wherein the wanted objects include cells, and the unwanted object includes an object that does not have at least one of the average size or the average shape of the cells, and wherein the controller is configured to at least one of (a) exclude at least one of the plurality of bins from the mean fluorescence value calculation if the at least one of the plurality of bins overlaps the unwanted object, or (b) assign a weight to at least one of the plurality of bins used in the mean fluorescence value calculation based on the proximity of the at least one of the plurality of bins to the unwanted object.