Simple, Easy Operation

Measurements with the LI‑840A are as simple as connecting a pump to the air inlet and passing the sample gas through the instrument's optical path. Data output features include:

  • Windows® Interface Software
  • Analog Outputs
  • Digital Outputs
  • XML Communications Protocol
LI-840A Software Main Window Screenshot
The LI‑840A communications software main window displays CO2 and H2O concentration, and status of settings.

The LI-840A easily integrates into control systems. User-defined 0-5 V high and low alarm relay outputs allow control of CO2 and/or H2O within a desired range. For example, the analyzer can be configured to trigger exhaust fans in a greenhouse to vent excess CO2 or H2O. These relays can also trigger devices such as automatic dialers, audible alarms, pumps, or valves in industrial applications. Activated alarms are also indicated by LEDs on the instrument top panel.

The LI-840A is powered by a 12-30 VDC source. Batteries or AC power can be used to power the instrument. Low power consumption (~ 0.3 A @ 12 V average after warm-up) makes the LI-840A suitable for a wide range of applications where power is limited.

Proven Technology

The LI-840A optical path is a thermostatically controlled IR detection system that provides excellent stability. Integrated thermistors and a pressure transducer provide for high accuracy in the concentration calculation over the entire measurement range.

Key Features of the LI-840A Optical Bench:

LI-840A detector
  • Gold-plated reflectors and optical path increase energy transmission.
  • Narrow band optical filters allow simultaneous measurement of CO2 or H2O in a single path.
  • The optical path is in direct contact with the source and detector housings to achieve thermal equilibrium.
  • A pressure transducer within the gas flow path minimizes variability due to changes in barometric pressure.
  • A foam enclosure surrounding the optical path maintains a controlled thermal environment and protects the bench from mechanical shock and vibration.

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