Design of microsensor for gases and liquids flow measurements (original) (raw)
Related papers
Microthermocouples Sensors for Velocity and Temperature Measurements in Gas Flow
Volume 2: Applied Fluid Mechanics; Electromechanical Systems and Mechatronics; Advanced Energy Systems; Thermal Engineering; Human Factors and Cognitive Engineering, 2012
This paper presents the development of two classes of sensors based on microthermocouples with different wire diameters (from 7.6 µm to 25.4 µm). The first one uses the pulsed-wire technique for the couple velocity/temperature measurement. These sensors are used with three different techniques we developed in our laboratory: the time of flight method, the oscillation frequency method and the phase method. Because the purpose of this kind of sensor is to be introduced in different microdevices, it is realized with two thermocouple wires and does not use the micromachining technologies. Its working principle is close to that of the hot wire anemometer and it presents the same advantages such as very small dimensions and weak response time. The sensor is developed in order to measure flows and temperatures in microsystems like small channels (width < 500 µm), microtubes (diameter < 53 µm) and small structures (volume < 100 µm 3 ). The second class of sensors are based on the multiwire thermocouple technique. In this paper we present a probe using two wires of same nature but different in diameter located close together at the measurement point. This probe is used to measure simultaneously the temperature and the velocity of flowing gas. Results will focus on oscillating flows of gas.
2014
To design an integrated thermoresistive micro calorimetric flow (TMCF) sensor for gases and liquids, it is essential to develop a compact analytical model as a function of Prandtl number (Pr). In this paper, we present a simple one-dimensional (1D) model of a thin film based TMCF sensor for different fluids. The proposed model, validated by the CFD simulations and experimental data, is used for systematically studying the effect of key design parameters on the sensor performance. The normalized 1D model can be applied to the system-level design of TMCF sensors for different types of fluids.
Thermal and mechanical analysis of micromachined gas sensors
Journal of Micromechanics and Microengineering, 2003
In this paper, we present a complete thermomechanical study of a micromachined gas sensor substrate. The work has been carried out combining coupled electrothermomechanical three-dimensional finite element modelling simulations with electrical, infrared thermography and interferometric microscopy experimental measurements. The performances predicted by simulations, such as the power consumption (heating efficiency in air of 5.7 • C mW −1), the time response (19 ms), the membrane deflection during operation and the preferential failure sites in the micromachined substrate have been confirmed by experience. Their good agreement validates the model, and allows us to consider the adaptability of this design as a micromachined substrate for integrated gas sensors.
Microfluidics and Nanofluidics, 2009
Micro-electro-mechanical system (MEMS) devices integrate various mechanical elements, sensors, actuators, and electronics on a single silicon substrate in order to accomplish a multitude of different tasks in a diverse range of fields. The potential for device miniaturization made possible by MEMS micro-fabrication techniques has facilitated the development of many new applications, such as highly compact, non-invasive pressure sensors, accelerometers, gas sensors, etc. Besides their small physical footprint, such devices possess many other advantages compared to their macro-scale counterparts, including greater precision, lower power consumption, more rapid response, and the potential for low-cost batch production. One area in which MEMS technology has attracted particular attention is that of flow measurement. Broadly speaking, existing micro-flow sensors can be categorized as either thermal or non-thermal, depending upon their mode of operation. This paper commences by providing a high level overview of the MEMS field and then describes some of the fundamental thermal and nonthermal micro-flow sensors presented in the literature over the past 30 years or so.
Modelling and design of microflow sensors based on measuring of temperature
2008 16th Mediterranean Conference on Control and Automation, 2008
The paper presents the design and experimental experience with the gas flow measurement instrument for the range of (5-25) ml/hr. The aimed application area is in a biochemical laboratory for the study of reaction kinetic of sediments decomposition in waste water. The time-of-flight type of sensor with one upstream and one downstream temperature sensor has been chosen for the study. We explain the basic operation principles of the tiny flow measurement and the sensor structure. In the numerical model paragraph, we are describing the basic configuration model and the modelling results. As the three-dimensional simulation would be very time consuming process, we have simplified the simulation for only two-dimensional task. The presented diagrams are derived for different gases (air, nitrogen, carbon oxide and chlorine) and sensor tube materials, namely steel, copper, and plexi-glass. We present also the experimental setup including the design and sensor parameters. The paragraph with experimental results and discussion on them illustrates the good correspondence with expected values. The paper concludes with the employment of designed gas flowmeter in the biochemical laboratory.
Single element thermal sensor for measuring thermal conductivity and flow rate inside a microchannel
Sensors and Actuators A-physical, 2021
The increasing development of continuous-flow applications in the field of microfluidics generates demand for in-line monitoring methods. The thermal conductivity (κ) of a liquid has been proven to be a valuable measurand for quality control, process monitoring, and analytical testing. However, most available methods for measuring κ of microliter-sized samples are limited for use on stagnant samples. In this work, a novel method and associated prototype device for measuring κ under flow conditions is presented. The so-called Transient Thermal Offset (TTO) method requires only a single metal resistive structure that is excitated with direct current (DC) pulses. To demonstrate the working, proof-of-principle experiments are performed on liquids with various κ under different flow rates. The results show that, after calibration, the presented microfluidic device can be used for accurately measuring κ of liquids under flow, as well as for determining the flow rate of liquids with a known κ. Within the explored ranges, both parameters can be determined with an average error of approximately 2.6%. The results confirm that, also under flow conditions, uncertainties concerning probing depth are eliminated with the TTO method.
Sensors and Actuators A-physical, 1993
A snnple to reahse micro-hqmd flow sensor wth hrgh senativlty 1s presented The sensor IS based on well known thermal anemometer pnnclples An analytIca model for the sensor behavlour apphcable for gas/hqmd fluids 1s presented The reahsatlon process of the sensor 1s described Model and expenmental results agree well The sensor 1s simple to Integrate Hrlth other micro-hqmd handling components such as pumps, mixers, etc @ 1993 -E&W Sequoia All nghts reserved
ACCURATE EXTRACTION OF THE TEMPERATURE OF THE HEATING ELEMENT IN MICROMACHINED GAS SENSORS
The sensitivity and selectivity of micromachined gas sensors strongly depend on the temperature of the heating element; therefore an accurate determination of this temperature is required. In this paper, a simple analytical model of the thermal behavior of a heating element placed onto a thermally insulated dielectric membrane is presented. It is demonstrated that simple resistance vs. power measurements are sufficient for a precise determination of the sensor temperature. These measurements performed "once and for all" at the wafer-level on the statistically relevant number of heaters, allowed us to determine a "universal" temperature vs. power curve.
International Journal of Thermophysics, 2010
A new method was proposed to measure the thermal conductivity of liquids with infinitesimal samples, which are much smaller than those required in conventional methods. The method utilizes a micro-beam-type MEMS sensor fabricated across a trench on a silicon substrate. Numerical analysis of heat conduction within and around a uniformly heated sensor showed that the temperature of a 10 µm long sensor reached a steady state within approximately 0.1 ms, after the start of heating. It was also revealed that the average temperature of the sensor at the steady state was higher in liquids with lower thermal conductivity. These results demonstrate a new idea of measuring the thermal conductivity of liquids within an extremely short time at a steady state before the onset of natural convection.