Search

In this article, a 3-D printed mechanical wind sensor with reduced measurement errors is demonstrated. This sensor consists of a cylindrical sensing structure arranged vertically in the center of a cross-shape cantilever. Eight strain gauges are symmetrically designed on the four beams of the cross cantilever to measure the airflow-induced cantilever deformation. With these eight strain gauges, two sets of Wheatstone full-bridge circuits can be constructed, enabling the measurement errors of the mechanical wind sensor to reduce remarkably. The experimental results indicate that, compared with the four-strain-gauge mechanical wind sensor in the previous work, the eight-strain-gauge design presented in this article can achieve a 62.4% sensitivity improvement for wind speed measurement. This increased sensitivity allows the wind sensor to realize a maximum speed measurement error of 0.53 m/s in the range of 0–30 m/s, achieving a 39.1% reduction compared with 0.87 m/s of the previous four-strain-gauge sensor. In addition, the test results also show that the proposed full-bridge sensor can define the airflow direction over the full range of 360° with a maximum error of 6°, which is 2° less than the four-strain-gauge device. [ABSTRACT FROM AUTHOR]

In this paper, the effect of sensing-structure taper ratio on two-dimensional (2-D) mechanical wind sensors is demonstrated for the first time. The mechanical wind sensor consists of a sensing structure vertically arranged in the center of a cross cantilever. It detects the wind speed and direction by measuring the airflow-induced cantilever deformation with eight strain gauges attached to the beam surface. Five forms of sensing structures with different taper ratios are designed and manufactured to investigate their effects on the performance of 2-D mechanical wind sensors. A series of experiments are conducted and the results reveal that the taper ratio of the sensing structure can affect the measurement range and the sensitivity of the 2-D mechanical wind sensor. A lower taper ratio results in a higher critical wind speed, which makes the mechanical wind sensor a wider measurement range. Moreover, the results also show that a wider measurement range usually means a lower sensitivity for a single device, and hence the measurement range and the sensitivity of the mechanical wind sensor are a contradiction. The effect rule of the taper ratio presented in this paper can provide a valuable reference for the design and manufacture of 2-D mechanical wind sensors. [Display omitted] • This paper systematically investigates the effect of sensing-structure taper ratio on two-dimensional (2-D) mechanical wind sensors for the first time. In previous work, our group found that once the wind speed exceeded a certain critical value, the cylinder sensing structure of the mechanical wind sensor would vibrate violently, causing the sensor output to shake severely. The presence of this vibration makes the motion of the sensing structure deviate from the prediction of Bernoulli law, and the detection capability of the mechanical wind sensor for higher wind speed is limited. • In the field of fluid mechanics, the wind-induced vibration of circular cylinders placed normal to the flow has been investigated extensively, and the taper ratio of the cylinder has been proved to have important impacts on the critical wind speed. Therefore, in this paper, cylinder sensing structures with different taper ratios are utilized to construct the mechanical wind sensors, and the effects of the taper ratios on the sensor performance are systematically explored by experiments. Based on this investigation, the relationship between the sensing-structure taper ratio and the sensor performance can be clarified, and the mechanical wind sensors can achieve optimized performance. The experimental results presented in this paper can provide a valuable reference for the design and manufacture of 2-D mechanical wind sensors. [ABSTRACT FROM AUTHOR]

In this paper, the design, fabrication, and characterization of a robust MEMS thermal wind sensor utilizing ceramic film packaging are proposed. The ceramic film is fabricated by means of low temperature co-fired ceramic (LTCC) technology, achieving the excellent adhesion between silicon substrate and ceramic film without any thermal adhesive. The most important is that the adverse effects of the packaging on the performance of the thermal wind sensor can be minimized by adjusting the thickness and thermal conductivity of the ceramic film during the preparation of the ceramic slurry. The influences of thickness and thermal conductivity of ceramic film on the performance of sensor have been simulated by finite element method, and the results are in reasonable agreement with theoretical analysis. The proposed sensors were tested and calibrated in a wind tunnel. Experiments results demonstrate that the sensitivity of the proposed sensor is decreased only 4.7%, compared with the sensor without ceramic film. The maximum measurement error of the proposed sensor in wind speed and direction is 0.66 m/s and 5°, respectively. Compared with the sensor packaged with $250\mu \text{m}$ ceramic carrier, the heating power of the proposed sensor is reduced by nearly 50% and the sensitivity is increased by an order of magnitude at the same time. [ABSTRACT FROM AUTHOR]

This paper presents a semi-empirical model for the temperature effect of a micromachined 2-D anemometer. The anemometer consists of a self-heated double Wheatstone bridge. Eight thermistors are symmetrically arranged in two orthogonal directions, and four of them in each direction make up a Wheatstone bridge. The eight thermistors simultaneously act as both heating and sensing elements. The terminal voltage across the bridge and the bridge output voltage, under the constant current supply, are utilized to measure the wind speed and direction, respectively. The semi-empirical model has taken the thermal physical properties of the air, sensor substrate, and thermistors into account. It shows that the measurement of wind direction has a weak temperature dependence due to the symmetric config uration of the self-heated double Wheatstone bridge, which suppresses the temperature drift. The temperature compensation has been performed by means of the semi-empirical model. The experimental measurements demonstrate that, when the air temperature changes from 270 to 310 K, the wind speed varies from 0 to 30 m/s with an error less than ±1.5 m/s while the wind direction spans from 0° to 360° with the weak temperature dependence. [ABSTRACT FROM AUTHOR]

A self-heated double Wheatstone bridge configuration for a 2-D wind sensor is presented. Without a central heating element, eight thermistors are symmetrically arranged in two orthogonal directions, and four of them in each direction make up a Wheatstone bridge. The eight thermistors simultaneously act as the heating sources and temperature sensing elements. By applying the constant current supply to the bridge, the terminal voltage across the bridge and the bridge output voltage are utilized to measure the wind speed and direction, respectively. The 2-D wind sensor has been simulated numerically and fabricated directly on the ceramic substrate. Experiments demonstrate that the measured speed varies from 0 to 40 m/s with an error less than ±2 m/s while the measured direction spans from 0° to 360° with an error less than ±3° after calibration. The double bridge configuration greatly simplifies the measurement and control circuits for the 2-D wind sensor. [2018-0171] [ABSTRACT FROM AUTHOR]

This paper introduces a novel sensing element scheme to improve the accuracy of 2-D micromachined thermal wind sensor. The sensing element consists of eight heaters and eight thermistors placed on ceramic substrate. The octagon-arranged sixteen resistors are divided into two wind sensing groups, cross-type group and saltire-type group. These two groups monitor wind independently, and the final measured wind speed and direction are extracted from the measurement results of the two groups. Based on this octagon-sensing design, the sensor achieves higher accuracy for wind measurement, which is verified by the experiment. The results show that for the wind speed up to 33 m/s, the sensor has a measurement error less than ±1%, and the airflow direction over the full range of 360° is determined with a maximum error of ±1.5°. [2018-0045] [ABSTRACT FROM AUTHOR]

This paper presents the design, fabrication, and performance of a micromachined silicon thermal wind sensor with improved sensitivity. Deep reactive ion etching (DRIE) trenches are fabricated between the heater and the thermistors to suppress the lateral heat conduction in the chip. In addition, eight thermistors symmetrically arranged in four directions around the heater form two Wheatstone full-bridges, resulting in about 50% increase of the sensitivity with respect to four thermistors. Based on these two methods, the sensitivity of the micromachined silicon thermal wind sensor is improved remarkably, which is verified by the experiment. The results show that the measurement wind speed range is up to 33 m/s in constant voltage (CV) mode with the initial heating power of 256 mW. The sensitivity is measured to be 29.37 mV/ms−1 at the wind speed 3.3 m/s, achieving improvement of about 226%, compared with that of the traditional wind sensor. Wind direction measurement results show that airflow direction over the full range of 360° is determined with an accuracy of ±5°. [2017-0052] [ABSTRACT FROM AUTHOR]