A method for measuring optical signal detector performance that includes directing light emitted from an optical signal detector onto a first non-fluorescent surface portion in a first detection zone of the optical signal detector. A first characteristic of light detected by a first sensor of the first optical signal detector is measured while the first non-fluorescent surface portion is in the first detection zone of the optical signal detector. Light emitted from the optical signal detector is directed into a first void in the first detection zone of the optical signal detector. A second characteristic of light detected by the first sensor of the optical signal detector is measured while the first void is in the first detection zone of the optical signal detector. And an operational performance status of the optical signal detector is determined based on at least one of the first characteristic and the second characteristic.