The present invention provides methods and devices for determining end of life of a light fixture by comparing the light output of a control LED of the fixture with the light output of an illumination LED of the fixture. The control LED is energized for a short period of time for the purpose of measuring its light output. The illumination LED is energized for the duration of time of the light fixture itself. In this way, the amount of degradation of the illumination LED can be determined by comparison with the control LED. If the light output of the illumination LED falls below a threshold level, actions may be take, such as, for example, sounding an alarm.

Systems and methods are disclosed for detecting the concentrations of constituent gases in a sample. Systems may include a sample chamber configured to contain a volume of a gas, a light source configured to emit infrared light through the volume of the gas, a reference channel, a plurality of active channels, and processing circuitry. The reference channel and the active channels can each include a bandpass optical filter configured to receive light from the light source and selectively pass a portion of the light within a unique range of wavelengths, and a photodetector configured to detect infrared light from the light source that passes through the bandpass optical filter. The processing circuitry can be configured to calculate the concentrations within the sample gas of a plurality of constituent gases based at least in part on the light detected at each of the photodetectors.

Method of generating a correction function for a light-emitting diode (LED) testing process, including: detecting light emitted by a reference LED and reflected from inactive LEDs on a panel within a field of view of a detector; varying a number of the inactive LEDs to derive uncorrected values of an optical parameter as a function of the number of inactive LEDs; detecting light emitted by the reference LED, or by an active LED having identical optical properties, in the absence of any other LEDs, to determine at least one reference value for each optical parameter; and calculating differences between the uncorrected values and each reference value to generate the correction function, the correction function being based on the number of inactive LEDs which are arranged within the field of view of the detector in the light detecting step.