LI-820 Description

Operating Principle

The LI-820 analyzer is a single beam, dual wavelength NDIR sensor. The CO2 measurement is a function of the absorption of IR energy as it travels through the optical path.

The IR source emits radiation into the optical path, where CO2 absorbs photons of a certain wavelength. The CO2 sampling channel uses an optical filter centered at 4.26 micrometers, corresponding to the absorption band for CO2. A filter with a center wavelength of 3.95 micrometers serves as a reference channel. The detector measures the strength of the signal that passes through the optical path; the ratio of the sample and reference signals indicates the amount of light absorption by CO2, and thus, the gas concentration.

Optical benches can be easily cleaned.

Making Measurements

The LI-820 is a very simple gas analyzer to use.  A pump is used to connect to the inlet port so that air will pass through the optical path and exit through the outlet port.  You have a choice of Windows® software (included), a datalogger, such as the LI-1400 Datalogger, or the XML communication protocol to set up your measurement protocol and collect data.  Real time numeric or graphic data can be viewed using the Windows® software.  You can also use either the Windows® software or the XML communication protocol to zero and span the analyzer.

Sophisticated Measurement Technology

The LI-820 optical path is a thermostatically controlled IR detection system that provides excellent stability over both time and temperature, which extends the required interval for calibration. Integrated thermistors and a pressure transducer provide for high accuracy in the concentration calculation over the entire measurement range.