Overview of the Optical Source, Detector, and Optical Path

The LI-840A analyzer was designed for easy replacement of parts as they reach the end of their life cycle or if they are damaged from environmental elements (water pulled into the Analyzer, electrical surges, etc).

The LI-840A’s source has an expected life-cycle of 18,000 hours. This would equate to just over two years if the instrument is used in continuous operation. When the Source begins failing, there may be highly variable spikes in the CO₂ concentration data. Eventually the Source will burn out and the Analyzer will only read zero or negative values for the CO₂ concentrations.

The detector will normally have an indefinite life cycle, but it can be cut short by water ingress or electrical surges.

The optical path can be easily cleaned using a mixture of alcohol and water as described in the LI-840A Instruction Manual (Section 5). However, if the Analyzer was ever to pull in a corrosive solution, this might permanently damage the gold-plating of the optical path. In this case, the optical path can easily be replaced.

After replacing any of the above components, the LI-820 Analyzer would need to be re-calibrated by setting the 'zero' (with a CO₂-free gas, such as nitrogen) and setting the 'span' (with a known and accurate standard CO₂ concentration).

Click on the following link for parts and instructions on replacing the source, detector, and/or optical path.

Contact LI-COR to obtain the replacement parts.