Patent ID: 7180594

Claim:
A method to test a photometric device usable for a light absorbance application, the method comprising the steps of: i) changing a signal supplied to a light source of the photometric device, the supplied signal usable to activate the light source to emit light; ii) obtaining a first signal representative of the light emitted from the light source; iii) obtaining a second signal representative of the light emitted from the light source after at least some of the emitted light has passed through an optical gap of the photometric device; and iv) determining whether the photometric device is operating properly based on a comparison between: a) an obtained value, associated with either one or both of the first and second signals, and b) at least one reference value, wherein the determining can be performed independently of whether any of the emitted light is absorbed as it passes through the optical gap, and wherein steps i) through iv) are automatically performed in-situ while at least a portion of the photometric device is immersed in a medium having cells growing therein and wherein the results of steps i) through iv) are logged by a control system.