infrared temperature sensor

Apogee IRT sensor for plant canopy and leaf temperature


  • An infrared thermometer, or radiometer, for continuous measurements of canopy or leaf temperature
  • Ideal for continuous, non-contact measurements of leaf and/or plant canopy temperature
  • Measurements are related to plant water use, crop water stress, drought-strategies, and nutrient uptake
  • Measure leaf-to-air temperature differences for plant physiological and research projects
  • SDI-12 outputs
  • Monitor related variables such as meteorological, transpiration and soil moisture

The Apogee IRT infrared temperature sensors offers intelligence in a rugged, easy-to-use package. The IRT sensor is centered around a high-speed microprocessor that continuously monitors and adjusts the complete system. While performing the complex algorithms determining the output, it calibrates itself about once every second, removing any concerns over drift or sudden changes.

Other advanced features include emissivity shift compensation and ambient radiation error correction. The rugged housing withstands thermal and mechanical shocks. The built-in air purge prevents dust, dirt, or condensing vapors from depositing on sensor optics, assuring long-term accuracy under all environmental conditions. The integral heat exchanger eliminates drift by automatically warming (or cooling) supply air to match the optical aperture temperature.

The output cable length should be specified in the order if required.

Every sensor is individually tested and calibrated within the measurement range.


canopy temperature and plant water potential

Canopy Infrared Temperature Water Potential

An example of the strong correlation between canopy temperature (Tc-Ta) and leaf water potential. (Image source: Gonzalez-Dugo et al, 2012, Fig.5)

A common application for the Apogee IRT Canopy Temperature Sensor is to measure leaf, or plant, water potential. A large amount of scientific research has demonstrated that there is a direct, and strong, correlation between the temperature of a leaf/canopy and water potential (see example figure to the right). Therefore, the Apogee IRT Canopy Temperature Sensor can be used to measure the water status of plants.

Canopy temperature increases and decreases throughout the day with ambient air temperature. A healthy canopy, with access to ample soil moisture, will have a high rate of transpiration which acts as a cooling effect. The process is similar to how humans sweat or perspire when we exercise to remain cool. A well irrigated and healthy plant will show a large temperature difference when compared with ambient air temperature. This is also known as the Leaf-to-Air, or Canopy-to-Air, Temperature Difference (also commonly expressed as Tc - Ta).

A plant under stress, particularly soil moisture stress, will show a lower Canopy-to-Air Temperature Difference. When soil moisture becomes limiting, the stomata on leaves begin to close which limits the rate of transpiration. Under this scenario, plants have a limited ability to cool the canopy via transpiration loss. In other words, plants are still exercising yet their perspiration has decreased. Therefore, the canopy temperature increases.

Scientific research has demonstrated that the increase in canopy temperature is directly related to the water status of the plant. As plant's become less hydrated, or as leaf water potential becomes more negative, the Canopy-to-Air Temperature Difference also decreases.

Leaf to Air Temperature Difference

An example of how canopy temperature is related to ambient air temperature over a 24 hour cycle.

The close relationship between canopy temperature and leaf water potential has significant benefits for researchers and growers. Measuring leaf water potential, for example with a pressure chamber, can be time consuming and laborious. Sensors that can continuously measure leaf water potential, such as a psychrometer or Zim probe, are also unreliable, expensive and extremely fragile. The Apogee IRT Canopy Temperature Sensor has advantages over these techniques because it is:

  • low cost
  • low maintenance
  • easy to install
  • and can connect to a data logger for continuous monitoring

Furthermore, Edaphic Scientific can install a infrared temperature sensor system with an alarm or SMS alert. When canopy temperature becomes high, an alarm or alert is sent and growers can undertake management to decrease canopy temperature and prevent crop stress.


whole system monitoring solutions

Edaphic Scientific is a one-stop shop for a whole system monitoring solution. We provide plant and soil monitoring systems for researchers and growers.

Our systems not only support dendrometers, but related sensors such as sap flow, soil moisture, weather parameters, and more.

At Edaphic Scientific we want to work with you from the start of your project through to its completion. We can provide:

  • Assistance with project and experimental design
  • Procurement of all monitoring equipment, including sensors, data loggers and data management software. Edaphic Scientific is a one-stop shop where we can source and find any necessary equipment for your project from our preferred suppliers or third party suppliers
  • Installation and training
  • On-going assistance with data interpretation and equipment maintenance
  • Data correction and analysis, including statistical analysis with the R-package
  • Report and publication preparation including tables, figures, graphs, and manuscript writing


advanced data collection and management solutions

Edaphic Scientific recognises the need for flexible and adaptable sensor and data logging solutions for experimental or environmental monitoring projects.

Data can be downloaded directly in the field from data loggers. A direct connection between the data loggers and your computer, via a USB cable, can be used for manual downloading of data.

Alternatively, data can be downloaded over the internet on your iPhone, iPad or desktop computer with the cloud-based, data management software solutions. Through this remote based downloading capabilities, you can download, view and manage your data, and system, anywhere in the world and at anytime.


feature specification
Measurement Range -30 to 65 ℃
Measurement Accuracy ±0.2 ℃
Repeatability < 0.05 ℃
Output SDI-12
Supply Voltage 5.5 to 24 VDC
Current Draw 1.5 mA (quiescent), 2.0 mA (active)
Field of View (FOV) 22 degrees
Update Time 0.6 seconds
Emissivity Setting 0.9, Fixed
Spectral Response 5.5 to 14 μm
Operating Temperature -50 to 80 ℃
Relative Humidity 100% non-condensing
Dimensions 23 mm diameter, 60 mm length
Probe Weight 190 g (with 5m cable)
Cable length between signal conditioner and data logger 5 m (standard) | maximum: 60m for SDI-12
Warranty 1 year

manual & docs

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