Airborne Research and Innovation

Licor Li7500 IRGA

A Licor Li7500 IRGA provides fast response (20Hz) carbon dioxide and humidity measurement.

A Licor Li7500 open path infrared gas analyser is used on the ECO-Dimona for high frequency sampling of humidity and CO2. The high frequency humidity meausurement is used to support the 3D wind calculation based on the BAT turbulence probe, as well as estimation of latent heat flux by the airborne eddy covariance technique. Similiarly the CO2 measurement is used in the estimation of CO2 fluxes via eddy covariance.

The Li7500 sensor head is mounted to the side of the ECO-Dimona's left hand underwing pod. It is rigidly mounted inside a housing designed to prevent any vibration of the sensor and to provide the required ancilliary measurements of temperature and pressure within the measurement path. The mount also incorporates the intake ports for the humidity and Picarro systems, with additional intake capacity for future systems.

The left hand side underwing pod in the lab
The Li7500 sensor head housing (2019 fit) on the left hand under-wing pod, during development.

The electronics for the Li7500 system are housed in the main MET system enclosure within the pod, where they are environmentally protected and temperature-stabilised.

Basic Specifications

Detector: Thermo-electrically cooled lead selenide.

Bandwidth: 5, 10, or 20 Hz, software selectable.

Operating Temperature Range: -25 to 50°C (-40 to 50 °C verification test available on request).

User Interface: Windows® based software supports all setup, configuration and calibration functions through RS-232 serial port.

Outputs: RS-232 (20 Hz Maximum) SDM (>40Hz) 2 user scalable 16 bit DACs updated at 300 Hz.

Auxiliary Inputs: 2 channels for temperature and pressure sensors (during calibration). Auxiliary Input with pressure sensor: 0-4.096V (±5V common mode rejection).

Power Requirements: 10.5 to 30 volts DC.

Power Consumption: 30 W during warm-up, 10 W in steady state

Weight: Head: 0.75 kg (excluding mount)