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Category: LI-820/LI-840A

Zero and Span Gas Guidelines

Zero and Span Gas Guidelines

LI-COR technical support often receives questions about choosing a set of CO2 calibration gases for our analyzers.   While we realize that every customer’s measurement situation may be slightly different, we do have a few suggestions for selecting a set of calibration gases.

We recommend having a zero gas, or the equipment to perform a chemical zero at the very least.  A zero gas is best if the gas is really CO2-free.   It’s not necessary to purchase pure nitrogen or argon…

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Temporary Fix for a Bad IR Source

Temporary Fix for a Bad IR Source

The infrared (IR) source for the LI-8xx series analyzers has an operational life of better than 20,000 hours, or about two years of continuous use. The IR source is essentially an incandescent light bulb, and fails as a result of the filament thinning with use as it burns away. Eventually the filament becomes thin enough that it cracks and breaks, at which point the source no longer works.

The permanent fix for a failed source is to replace it with…

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LI-820, LI-840/A, LI-8100/A, and terrible, horrible, no good, very bad data

LI-820, LI-840/A, LI-8100/A, and terrible, horrible, no good, very bad data

There are four common causes for bad readings on LI-8xxx instruments:

  1. Incorrect zero and span calibration parameters.
  2. IR light source that is failing or has failed.
  3. Contamination (dirt, corrosion, liquids) in the optical path.
  4. Failed detector.

1)  Incorrect zero and span calibration parameters:

Check these values using the LI-COR interface software for each instrument by going to:

For LI-820 and LI-840, LI-840A: View – Calibration – Advanced

For the LI-8100, LI-8100A: Utilities…

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Obtaining Calibration Coefficients for Your LI-COR Gas Analyzer(s) Online

Obtaining Calibration Coefficients for Your LI-COR Gas Analyzer(s) Online

The calibration coefficients for LI-COR gas analyzers are factory installed, or may be re-entered if the instrument is returned for service at LI-COR. If the original calibration certificate that was sent with the instrument is misplaced, you can get a copy of it from LI-COR’s technical support web page by following these steps:

1. Go to http://www.licor.com/env/support/ and scroll down until you see the following:

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Carbon Isotope Considerations for LI-COR Gas Analyzers

Carbon Isotope Considerations for LI-COR Gas Analyzers

Carbon isotope tracing and analysis can provide valuable information about the path of specific molecules through a plant or an ecosystem.   Typically, a naturally-occurring isotope is introduced at a different concentration than that which is normally present in the natural environment, and then the isotope is traced through the system in question to illuminate ecosystem or plant processes.

All LI-COR infrared gas analyzers are designed to measure the three most common isotopes of carbon (12C, 13C, and 14C), but their…

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