Abstract
This study proposes a wireless remote weather monitoring system based on Micro-Electro-Mechanical Systems (MEMS) and wireless sensor network (WSN) technologies comprising sensors for the measurement of temperature, humidity, pressure, wind speed and direction, integrated on a single chip. The sensing signals are transmitted between the Octopus II-A sensor nodes using WSN technology, following amplification and analog/digital conversion (ADC). Experimental results show that the resistance of the micro temperature sensor increases linearly with input temperature, with an average TCR (temperature coefficient of resistance) value of 8.2 × 10−4 (°C−1). The resistance of the pressure sensor also increases linearly with air pressure, with an average sensitivity value of 3.5 × 10−2 (Ω/kPa). The sensitivity to humidity increases with ambient temperature due to the effect of temperature on the dielectric constant, which was determined to be 16.9, 21.4, 27.0, and 38.2 (pF/%RH) at 27 °C, 30 °C, 40 °C, and 50 °C, respectively. The velocity of airflow is obtained by summing the variations in resistor response as airflow passed over the sensors providing sensitivity of 4.2 × 10−2, 9.2 × 10−2, 9.7 × 10−2 (Ω/ms−1) with power consumption by the heating resistor of 0.2, 0.3, and 0.5 W, respectively. The passage of air across the surface of the flow sensors prompts variations in temperature among each of the sensing resistors. Evaluating these variations in resistance caused by the temperature change enables the measurement of wind direction.
Highlights
In recent years, emerging Micro-Electro-Mechanical Systems (MEMS) technology and micromachining techniques have been a popular approach to the miniaturization of sensors
The piezoresistors used in the pressure sensor [Figure 2(c)] and the resistors utilized in the flow sensor [Figure 2(d)] were deposited over silicon nitride membranes of the same dimensions (3,000 μm × 3,000 μm), which were released by a back-etching process to form a heat insulating membrane over the thermal flow sensor
This study conducted a systematic investigation of the performance of the fabricated sensor array of the MEMS-based weather monitoring system (Figure 4)
Summary
In recent years, emerging Micro-Electro-Mechanical Systems (MEMS) technology and micromachining techniques have been a popular approach to the miniaturization of sensors. Previous studies have reported on the use of MEMS sensors for monitoring individual weather parameters, such as pressure [1], flow rate [2,3], humidity [4,5], temperature, and multi-parameters (two or more) [6,7,8,9,10]. Lee et al [11] described the use of Pt resistors as temperature sensors in MEMS-based temperature control systems. Lee and Lee [12] proposed micromachine-based humidity sensors, with integrated temperature sensors, for signal drift compensation. This study developed a MEMS-based device using thin-film platinum resistors as temperature sensing elements and a nitride-silicon microstructure suspended at a short distance above the surface of a glass substrate (with a stationary electrode) as the movable electrode of a capacitor
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