The present disclosure, among other things, describes a reader system for analyzing one or more analytes in a fluid sample, comprising a casing (204) with at least one port (201) leading to a holster (301) which is configured to receive a cartridge (107) comprising a vertically oriented immunoassay device for analyzing one or more analytes in a fluid sample, an optical system (121) with excitation optics comprising a light source (302) and an excitation lens (305) configured to transmit light from the light source (302) and thereby excite a region of the vertically oriented immunoassay device when a cartridge (107) is placed in the holster (301), and collection optics comprising a photosensor (306) and a collection lens (307) configured to collect emitted light from the vertically oriented immunoassay device when a cartridge (107) is placed in the holster (301), an electromechanical motor system (106) configured to move the holster (301) in a vertical direction with respect to the optical system (121) so that the optical system (121) can interrogate different regions of the vertically oriented immunoassay device when a cartridge (107) is placed in the holster (301), and one or more digital processors (104a, 104b) and associated electronics configured to receive data from and control the optical system (121) and to control the electromechanical motor system (106).