Evaluation of a wireless infrared thermometer with a narrow field of view

Abstract

Many agricultural studies rely on infrared sensors for remote measurement of surface temperatures for crop status monitoring and estimating sensible and latent heat fluxes. Historically, applications for these non-contact thermometers employed the use of hand-held or stationary industrial infrared thermometers (IRTs) wired to data loggers. Wireless sensors in agricultural applications are a practical alternative, but the availability of low cost wireless IRTs is limited. In this study, we designed prototype narrow (10 •) field of view wireless infrared sensor modules and evaluated the performance of the IRT sensor by comparing temperature readings of an object (T obj) against a blackbody calibrator in a controlled temperature room at ambient temperatures of 15 • C, 25 • C, 35 • C, and 45 • C. Additional comparative readings were taken over plant and soil samples alongside a hand-held IRT and over an isothermal target in the outdoors next to a wired IRT. The average root mean square error (RMSE) and mean absolute error (MAE) between the collected IRT object temperature readings and the blackbody target ranged between 0.10 and 0.79 • C. The wireless IRT readings also compared well with the hand-held IRT and wired industrial IRT. Additional tests performed to investigate the influence of direct radiation on IRT measurements indicated that housing the sensor in white polyvinyl chloride provided ample shielding for the self-compensating circuitry of the IR detector. The relatively low cost of the wireless IRT modules and repeatable measurements against a blackbody calibrator and commercial IR thermometers demonstrated that these wireless prototypes have the potential to provide accurate surface radiometric temperature readings in outdoor applications. Further studies are needed to thoroughly test radio frequency communication and power consumption characteristics in an outdoor setting.

A crop water stress index and time threshold for automatic irrigation scheduling of grain sorghum

“…The system for remotely sensing crop water status with IRTs and meteorological instrumentation is variable depending on the number of IRTs and the manufacturer. However, with the advent of low-cost wireless sensors (Mahan et al, 2010;O'Shaughnessy et al, 2011) and sensor network systems (O'Shaughnessy and Evett, 2010), the cost is closer to the lower-end of the purchase price for a single neutron probe. Additionally automated systems using the center pivot as a platform for IRTs can be used to provide crop canopy temperature maps on a frequent basis (Peters and Evett, 2007), which will have better spatial and temporal resolution than weekly neutron probe readings.…”

Plant-Based Methods for Irrigation Scheduling of Woody Crops

“…There are non-expensive, robust, wireless models of IRT that are installed in the field for collecting T c readings with a frequency of seconds or minutes, and storing average values every minute or fractions of an hour [72,73]. Infrared thermometers perform better with low, homogeneous crops growing in regions with rather constant weather conditions [67].…”

Temperature Measurement of Photovoltaic Modules Using Non-Contact Infrared System

“…The MLX90614 is delivered factory calibrated with a digital output. Since the accuracy is specified when the sensor is in thermal equilibrium and under isothermal conditions, Melexis developed xCx series of sensors which internally measure the thermal gradients and the measured object temperature is compensated for them [18,19]. All this makes the MLX90614 superior over specifically made Pt100s and any other contact sensor in terms of costs, accuracy and simplicity because it is cheaper than a specifically made Pt100, it is compensated for ambient temperature in contrast to contact sensors, it does not have to be calibrated and it requires less of additional electronics.…”