Specifications

LI-720 Carbon Flux Sensor

General

  • Weight: 2.02 kg

  • Power Requirements:

    • Voltage: 9 – 33 VDC nominally; Can be powered from a standard USB port (2.0 or newer) for calibration and firmware updates. Outdoor operation from a 5 V USB power supply is not supported.

    • Power Consumption: 1.5 W

  • Communication Interface: SDI-12, RS-232 (10 Hz data); compatible with LI-COR IoE Modules and some data loggers

  • Operating Temperature Range: -25 – 50 °C

CO2 measurement

  • Calibration Range: 0 to 1500 µmol mol-1

  • Accuracy: Within 1.5% of reading

  • Zero Drift per °C: ±0.15 ppm typical, ±0.3 ppm maximum

  • RMS Noise: @10 Hz: 1.0 ppm (typical @ 400 µmol mol-1 CO2)

  • Direct Sensitivity to H2O: ±2.00E-05 typical, ±4.00E-05 maximum

  • Reporting Frequency: 10 Hz (samples per second)

H2O measurement

  • Calibration Range: 0 to 60 mmol mol-1

  • Accuracy: Within 1.5% of reading

  • Zero Drift (per °C): ±0.03 mmol mol-1 typical, ±0.05 mmol mol-1 maximum

  • RMS Noise: @10 Hz: 0.05 mmol mol-1 (typical @ 10 mmol mol-1 H2O)

  • Direct Sensitivity to CO2: ±0.02 typical, ±0.05 maximum

  • Reporting Frequency: 10 Hz (samples per second)

Wind speed measurements

  • Measurement Axes: U, V, W

  • Measurement Range: 0 – 30 m s-1 (horizontal wind)

  • W Offset at Zero Wind: ±0.06 m s-1

  • W Noise (1 standard deviation): <0.1 m s-1 at 5 m s-1, <0.15 m s-1 at 15 m s-1

  • Sonic Temperature Accuracy: ±0.7 °C maximum offset at 20 °C

  • Reporting Frequency: 10 Hz (samples per second)

Biomet measurements

  • Photosynthetic Photon Flux Density:

    • Range: 0-3000 µmol m-2 s-1

    • Accuracy: ±5% of reading

    • Cosine Correction: Corrected up to 75° angle of incidence

  • Air Temperature:

    • Range: -40 to 60 °C

    • Accuracy: ±1.5 °C; No solar load conditions

  • Atmospheric Pressure:

    • Range: 50 – 110 kPa

    • Accuracy: ±0.2 kPa

  • Relative Humidity:

    • Range: 0-100% – non-condensing

    • Accuracy: ±1% typical

Position and orientation

  • GPS: Provides location and precise time, including for edge flux processing

  • Magnetometer: Reports orientation relative to magnetic north (°)

  • Accelerometer: Reports instrument tilt (°)

Specifications subject to change without notice.

LI-720 dimensions.

Figure 11‑1. LI-720 dimensions. Additional clearance is required for the cable.

IoE Module

General

  • Operating Temperature Range: -25 to 50 °C
  • Operating Humidity Range: 0 to 95%, non-condensing
  • Storage Temperature Range: -40 to 65 °C; 85% RH
  • Ingress Protection: IP24 Rating
  • Enclosure Flame Rating: UL94-V-0
  • GNSS (GPS) Support: GPS receiver for time synchronization and location information.
  • Display: 35 x 55 mm; monochrome

Auxiliary power input

  • Input Voltage Range: 9 to 33 VDC (>11 V recommended for startup)
  • Maximum Current: 3.0 A

Digital inputs/outputs

  • SDI-12 ports: 2
    • Output Voltage: 12 V
    • Maximum Total Current: 2.5 A
  • Sensor Ports (SDI-12 'plus'): 1 (combined SDI-12 with fast serial T/R)
  • USB port: Micro-B connector

Structure and load

  • Ground Area Required:
    • Without Guy Wires: 42 × 107 cm (16.25 × 42 inches)
    • With Guy Wires at 15°: 244 × 244 cm (96 × 96 inches)
  • Maximum Load on Mast: 4.54 kg (10 lbs.)
  • Maximum Battery Weight: 45.4 kg (97 lbs.)
  • Soil Types for Anchors: 1 to 4

Weights

  • System (total): <45.4 kg (<100 lbs.)
  • Battery: 24.9 kg (55.0 lbs.)
  • Solar Panel: 7.5 kg (16.5 lbs.)
  • Frame: 13 kg (28.7 lbs.)

Data

  • Data Storage: Removable Micro SD card; 8 GB. If the modem is offline, data are stored until connectivity is restored (storage for 2 weeks of data).
  • Data Format: Text; Comma-separated values (CSV)

Cellular

  • Wireless Protocols: LTE CAT1