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Enabling better global research outcomes in soil, plant & environmental monitoring.


The basic AGRI-THERM II Model 100L is Everest's simplest handheld infrared thermometer for taking temperature measurements outdoors in the natural environment. It is designed to measure only the surface temperature of the target.

The AGRI-THERM II (Model 100L) Infrared Thermometer takes readings in a fraction of a second over a temperature range of -40°C to 100°C with 0.1° resolution.

One standard feature on this instrument is the SKY-SPY™ System. To increase the accuracy of the AGRI-THERM II™, the SKY-SPY™ has been added to the original sensor. Errors from 1-2°C can result when an infrared sensor is calibrated indoors and then used outdoors. This is because the cold sky reflects off of the target’s surface and into the temperature sensor. This reflection combines with the target’s radiation signal, causing an error. This error is dynamic and unpredictable and can vary from 0.5°C to 2.0°C in a matter of minutes. For this reason, the SKY-SPY™ is vital to the accuracy of this particular sensor.

The AGRI-THERM II™ also incorporates the TTL/SLR Intra-Optical Light Sighting System wherein a light goes directly through the infrared optics, illuminating the exact target area being measured. The sighting of the actual target is not possible with conventional infrared thermometers. Since the infrared signal beam is not visible to the human eye, this light sighting feature is necessary to be sure that the target is being measured and not the target and the background. All infrared thermometers average the temperature of the first thing they see. With the TTL/SLR Intra-Optical Light Sighting, it is possible to know exactly what the thermometer is seeing.

The VARIO-ZOOOM™ Field-Variable-Focus System allows the operator to change the field of view of the infrared thermometer in the lab or field. This is accomplished by simply pulling the optics out or pushing them in. The TTL/SLR Intra-Optical Light Sighting will indicate when the instrument is in focus when the target spot size is clear. The optics will remain where they are focused as there are two rubber gaskets con-straining their movement.

The output of the AGRI-THERM II™ is Analogue Millivolt with 10mV/°C. Its standard Field of View (FOV) is four degrees with an optional fifteen (15) degree FOV available.


Temperature Measurement

Scale Range: -40°C to 100°C
Resolution: 0.1°C
Accuracy: ±0.25°C from 0°C to 50°C & ±0.5°C from -40°C to 0°C or 50°C to 100°C
Repeatability: ±0.1°C
Temperature: All functions in °C, corresponding to voltage output
Noise Effective Temperature: <0.1°C
Temperature Measurement Modes: Surface Temperature

Optical Considerations

Optical Configuration: Robust, aerospace-quality, double-coated zinc selenide optics
per military specification MIL-C-13508
Spectral Pass Band: 8 < Wavelengths < 14 Microns
Sighting: TTL/SLR Instra-Optical light sighting: Visible light illuminates field of view (Patent no. 4,494,881)
Illumination Source: Light Emitting Diode- Safe- No Lasers!
Field of View: Variable from 4° to 20° with Vario-Zoom™ field-variable-focus (Patent no. 7,355,178)
Display: Numeric Liquid Crystal Display on rear panel

Operating Conditions

Operating Environment: -20°C to 65°C (+14°F to 150°F), up to 99% relative humidity, non-condensing
Storage Temperature: Same as operating environment temperature

Electrical Interface

Power Sources: Rechargeable nickel metal hydride batteries.
10 hours continuous use on full battery charge.
Output Signal: Analogue Millivolt (-400mV to 1000mV at 10.0mV/°C)


Response Time: <1 second
Emissivity Compensation: Settable from 10% to 99% on rear panel
Sky Radiation Detection/Correction Standard Sky-Spy™ system for detection & correction of unwanted sky reflection (U.S. patent no. 4,420,265)
Operating Distance: 2cm to infinity
Embedded Data Logger (Optional): Custom made data logger; easy USB connection; Microsoft Excel format.
Warranty: One-year limited warranty on parts and labour

Ajayi, A. E., & Olufayo, A. A. (2004). Evaluation of Two Temperature Stress Indices to Estimate Grain Sorghum Yield and Evapotranspiration. Agronomy Journal, 96(5), 1282–1287. https://doi.org/10.2134/agronj2004.1282

American Society for Testing and Materials 2001, ‘Standard Test Methods for Radiation Thermometers (Single Waveband Type). Designation: E 1256 ñ 95 (Reapproved 2001)’, in 2001 Annual Book of ASTM Standards, American Society for Testing and Materials,, West Conshohocken.

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Irmak, S., Haman, D. Z., & Bastug, R. (2000). Determination of Crop Water Stress Index for Irrigation Timing and Yield Estimation of Corn. Agronomy Journal, 92(6), 1221–1227. https://doi.org/10.2134/agronj2000.9261221x

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Sadler, E. J., Bauer, P. J., Busscher, W. J., & Millen, J. A. (2000). Site-Specific Analysis of a Droughted Corn Crop: II. Water Use and Stress. Agronomy Journal, 92(3), 403–410. https://doi.org/10.2134/agronj2000.923403x