A high sensitivity single-probe heat pulse soil moisture sensor based on a single npn junction transistor

作者：Dias Pedro Carvalhaes; Roque Wellington; Ferreira Elnatan Chagas; Siqueira Dias Jose A

来源：Computers and Electronics in Agriculture, 2013, 96: 139-147.

DOI：10.1016/j.compag.2013.05.003

• Soil moisture sensors
• Heat dissipation sensors
• Single probe heat pulse sensors
• Precision agriculture

The classic technique for measuring soil water content using heat dissipation properties was employed to develop a new single probe heat pulse sensor (SPHP). The novel sensor is comprised of only one element, a npn junction bipolar transistor, which works as both heating and temperature sensing elements. The variations of V-BE(T) as a function of the temperature are used to measure the temperature of the sensor and, since the behaviour of V-BE(T) is one of the most well studied expressions that describe the bipolar transistor, the sensor's temperature can be easily measured, with high accuracy. A technique which increases simultaneously the collector-base voltage V-CB and the collector current I-C of the transistor allows for the application of the heat pulse with low level currents, in the order of 6 mA. The sensor developed in this work presented a Delta T-max range of 9.1 degrees C between wet and dry soil conditions (theta(nu) between 5% and 35%), while the current available heat pulse probe sensors present a typical Delta T-max range of only 1.5 degrees C, showing the potential benefits of using a single bipolar junction transistor as a high sensitivity soil water content measurement sensor.

• 出版日期2013-8