A reader system for analysing one or more analytes in a fluid sample comprised in a vertically oriented immunoassay device aligned to gravity, the system comprising: a. a removable cartridge comprising the vertically oriented immunoassay device for analysing one or more analytes in a fluid sample; b. a holster, in which are located i. the removable cartridge comprising the vertically oriented immunoassay device for analysing one or more analytes in a fluid sample; and ii. alignment features for ensuring alignment of the cartridge within the holster such that the vertically oriented immunoassay device is aligned to gravity; and c. a casing with at least one port leading to the holster; and d. an optical system with excitation optics comprising at least one light source and at least one excitation lens configured to transmit light from the light source and thereby excite a region of the vertically oriented immunoassay device, and collection optics comprising at least one photosensor and at least one collection lens configured to collect emitted light from the vertically oriented immunoassay device; e. an electromechanical motor system configured to move the holster in a direction aligned to gravity and vertically with respect to the optical system so that the optical system can interrogate different regions of the vertically oriented immunoassay device when said device is aligned to gravity; and f. one or more digital processors and associated electronics configured to receive data from and control the optical system and to control the electromechanical motor system; wherein the vertically oriented immunoassay device comprises multiple immunoassay channels, the excitation optics comprises multiple light sources, each with a different central wavelength, the collection optics comprises multiple photosensors, and the light sources and photosensors are configured in pairs so that they can simultaneously transmit light to and collect emitted light from different immunoassay channels, wherein the multiple immunoassay channels are spatially separated such that cross talk between different immunoassay channels and different photosensors is substantially absent when the multiple immunoassay channels are interrogated simultaneously by the multiple light sources and the multiple photosensors. a. a removable cartridge comprising the vertically oriented immunoassay device for analysing one or more analytes in a fluid sample; b. a holster, in which are located i. the removable cartridge comprising the vertically oriented immunoassay device for analysing one or more analytes in a fluid sample; and ii. alignment features for ensuring alignment of the cartridge within the holster such that the vertically oriented immunoassay device is aligned to gravity; and i. the removable cartridge comprising the vertically oriented immunoassay device for analysing one or more analytes in a fluid sample; and ii. alignment features for ensuring alignment of the cartridge within the holster such that the vertically oriented immunoassay device is aligned to gravity; and c. a casing with at least one port leading to the holster; and d. an optical system with excitation optics comprising at least one light source and at least one excitation lens configured to transmit light from the light source and thereby excite a region of the vertically oriented immunoassay device, and collection optics comprising at least one photosensor and at least one collection lens configured to collect emitted light from the vertically oriented immunoassay device; e. an electromechanical motor system configured to move the holster in a direction aligned to gravity and vertically with respect to the optical system so that the optical system can interrogate different regions of the vertically oriented immunoassay device when said device is aligned to gravity; and f. one or more digital processors and associated electronics configured to receive data from and control the optical system and to control the electromechanical motor system;