Device and associated methods for performing luminescence and fluorescence measurements of a sample

An optical reader subassembly comprising:

• a housing including an internal area;
• a container configured to hold a fluid sample at a sample position, placement of the container within the housing creating a light tight seal for the fluid sample at the sample position within the internal area of the housing;
• a light source configured to project light onto the fluid sample within the container;
• and
• an optical sensor configured to move between different sensor positions while the fluid sample remains stationary at the sample position, the different sensor positions including (i) at least one of a first sensor position for taking a luminescence reading of the fluid sample or a third sensor position for taking a fluorescence reading of the fluid sample, and (ii) a second sensor position that is optically isolated from the fluid sample for taking a dark current or other background measurement even when the light source is projecting light onto the fluid sample.