LI-840A Frequently Asked Questions

Q What is the measurement range for the LI-840A?

A The LI-840A measures CO2 ranging from 0 to 20,000 ppm. The H20 measurement ranges from 0 to 60 mmol/mol.

Q What is the difference between the LI-840 and the LI-840A?

A The LI-840A offers scalable digital-to-analog outputs and an extended range for measuring CO2. The original LI-840 had the capability to measure from 0 to 3,000 ppm whereas the LI-840A measures from 0 to 20,000 ppm. The LI-840A also offers new Windows Interface software.

Q Is there an upgrade available from the LI-840 to the LI-840A?

A There is an upgrade available for the new software. If you currently have an LI-840, you will need to send your instrument into LI-COR to receive the upgrade. To do this, please contact a representative at: or by phone at: 1-800-447-3576.

Q What are the main differences between the LI-840A and the LI-820?

A The LI-840A measures both CO2 and H2O, whereas the LI-820 only measures CO2. Because the LI-840A measures both CO2 and H2O, the accuracy of the CO2 measurement is higher for the LI-840A than the LI-820. Both instruments measure CO2 concentrations ranging from 0 to 20,000 ppm. LI-840A and LI-820 Comparison

Q Do I need a pump with my LI-840A?

A An external pump is required for the LI-840A. The pump should provide a flow rate between 0 and 1 liters per minute with this instrument. LI-COR offers a list of parts and vendors that offer pumps to move air through the analyzer. Specifications for this and a list of parts and vendors can be found at:

Q How do I power my LI-840A

A Power can be supplied by a 10.5-30VDC input voltage. Batteries or an optional AC adapter (part number 800-401) can also be used to power the LI-840A.

Q How can I log data with my LI-840A?

A Data can be logged to a computer with the LI-840A software or to a data storage device using XML, analog outputs (0-2.5 V or 0-5 V), or current outputs (4-20 mA). The LI-1400 Data Logger or other data logger would be suitable.

Q Can the LI-840A send an alert if my CO2 or H2O levels are out of my desired, set range?

A The high and low alarms can be configured to activate if CO2 or H2O levels are outside of a desired range. The alarms are typically used to activate an electronic trigger, which could control exhaust fans in a greenhouse, automatic dialers, audible alarms, pumps, or valves in industrial applications.

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