Abstract:Vacuum equipment has a wide range of applications, and vacuum monitoring in such equipment is necessary in order to meet practical applications. Pirani sensors work by using the effect of air density on the heat conduction of the gas to cause temperature changes in sensitive structures, thus detecting the pressure in the surrounding environment and thus vacuum monitoring. In past decades, MEMS Pirani sensors have received considerable attention and practical applications because of their advances in simple str… Show more
“…With the development of micromachining technology, the microelectromechanical systems (MEMS) thermal vacuum sensors demonstrate advantages of small size, fast response and low power consumption. Compared with MEMS piezoresistive and capacitive vacuum sensors, they do not need a vacuum cavity in terms of structure and pose a relatively wide pressure range with regard to performance [3,4], so they have been widely applied in many academic and industry fields [5,6].…”
MEMS thermal vacuum sensors have been widely applied in many academic and industry fields, and pressure range is a key performance of MEMS thermal vacuum sensors. To extend the pressure range, a combined MEMS thermal vacuum sensor that consists of two diode-type MEMS thermal vacuum sensors in series is proposed in this work. The two diode-type sensors are designed to have different areas of sensitive region and distances between sensitive region and heat sink, and their responses to the pressure are from 3.0 × 10−3 to 3 × 104 Pa and from 1.7 × 10−2 to 4.4 × 105 Pa, respectively. By series-connecting them, the combined sensor achieves a pressure range of 1.3 × 10−3 to 6.9 × 105 Pa without any additional control circuit. In addition, it possesses a relatively small size of 400 × 300 μm2. These indicate that the combined MEMS thermal vacuum sensor has the characteristics of wide pressure range, high sensitivity and small size.
“…With the development of micromachining technology, the microelectromechanical systems (MEMS) thermal vacuum sensors demonstrate advantages of small size, fast response and low power consumption. Compared with MEMS piezoresistive and capacitive vacuum sensors, they do not need a vacuum cavity in terms of structure and pose a relatively wide pressure range with regard to performance [3,4], so they have been widely applied in many academic and industry fields [5,6].…”
MEMS thermal vacuum sensors have been widely applied in many academic and industry fields, and pressure range is a key performance of MEMS thermal vacuum sensors. To extend the pressure range, a combined MEMS thermal vacuum sensor that consists of two diode-type MEMS thermal vacuum sensors in series is proposed in this work. The two diode-type sensors are designed to have different areas of sensitive region and distances between sensitive region and heat sink, and their responses to the pressure are from 3.0 × 10−3 to 3 × 104 Pa and from 1.7 × 10−2 to 4.4 × 105 Pa, respectively. By series-connecting them, the combined sensor achieves a pressure range of 1.3 × 10−3 to 6.9 × 105 Pa without any additional control circuit. In addition, it possesses a relatively small size of 400 × 300 μm2. These indicate that the combined MEMS thermal vacuum sensor has the characteristics of wide pressure range, high sensitivity and small size.
“…A typical Pirani gauge and thermistor gauge measure the change in filament temperature with pressure through the change of the resistance, and a thermocouple gauge measures the temperature of filament by means of a thermocouple [ 14 ]. The thermal conductivity vacuum gauges have experienced an improvement from having large volumes and difficulty in mass production to miniaturization of gauges by introducing MEMS (Micro-Electro-Mechanical-Systems) technology [ 15 – 17 ]. However, the MEMS thermal conductivity gauges have complex structures, and the fabrication process of some devices may be incompatible with the CMOS (the complementary metal oxide semiconductor) process, which increases the cost of gauges and relatively reduces their performance [ 17 ].…”
Section: Introductionmentioning
confidence: 99%
“…The thermal conductivity vacuum gauges have experienced an improvement from having large volumes and difficulty in mass production to miniaturization of gauges by introducing MEMS (Micro-Electro-Mechanical-Systems) technology [ 15 – 17 ]. However, the MEMS thermal conductivity gauges have complex structures, and the fabrication process of some devices may be incompatible with the CMOS (the complementary metal oxide semiconductor) process, which increases the cost of gauges and relatively reduces their performance [ 17 ]. Therefore, it is necessary to develop new types of vacuum sensors with a simple fabrication process.…”
A traditional thermal conductivity vacuum gauge mainly detects low pressure (the degree of vacuum) by measuring the temperature change of a filament heated by the electric current. We propose a novel pyroelectric vacuum sensor that utilizes the effect of ambient thermal conductivity on the pyroelectric effect to detect vacuum through the charge density of ferroelectric materials under radiation. The functional relationship between the charge density and low pressure is derived, which is validated in a suspended (Pb,La)(Zr,Ti,Ni)O
3
(PLZTN) ferroelectric ceramic-based device. The charge density of the indium tin oxide/PLZTN/Ag device under 405 nm of 60.5 mW cm
−2
radiation at low pressure reaches 4.48 μC cm
−2
, which is increased by about 3.0 times compared with that at atmospheric pressure. The vacuum can improve the charge density without increasing the radiation energy, confirming the important role of ambient thermal conductivity on the pyroelectric effect. This research provides a demonstration for ambient thermal conductivity effectively tuning pyroelectric performance, a theoretical basis for pyroelectric vacuum sensors, and a feasible route for further optimizing the performance of pyroelectric photoelectric devices.
“…Micro Electro Mechanical Systems (MEMS) technology has led to the development of miniature vacuum sensors with many advantages over conventional vacuum gauges such as lower power consumption, higher measurement sensitivity, improved dynamic range, smaller volume, and lower fabrication costs. The common type of MEMS vacuum pressure sensor is based on thermal conductivity or membranebased measurements like a, Pirani gauge [2], ionisation gauge [3] or based on change in resonance frequency [4]. Touch mode capacitive vacuum pressure sensors to detect absolute [5] and differential vacuum pressures have also been reported * Author to whom any correspondence should be addressed.…”
Knudsen forces are gas molecular forces, generated due to the presence of a thermal gradient between two surfaces in rarefied gas and can be effectively used for the measurement of low pressures. This work reports on a Knudsen force based MEMS low pressure sensor consisting of two stacked beams of polysilicon- one acting as a heater while the other as a sensor. The structure is fabricated using a double sacrificial layer surface micromachining process. The thermal gradient across the two stacked beams is induced by resistive heating of the heater beam. The effect of using two separate beams for heating and sensing has been investigated at different heater current and the results are compared with the existing works. The provision of two beams has resulted in the sensor functioning at very low pressure of less than 0.1 Pa with an improved sensitivity of 15.5 fF/mPa.
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