Optimized MEMS Pirani sensor with increased pressure measurement sensitivity in the fine and high vacuum regime

Abstract

An optimized microelectromechanical systems Pirani sensor with increased sensitivity for pressure measurements in the fine and high vacuum regime (from 100 to 10−6 Torr) is presented. Theoretical calculations of the signal voltage as a function of pressure are in good agreement with the measured voltage–pressure response. Fabrication technologies, design optimization using thermal modeling and finite element method simulations, and measurement results are presented.

Design and Simulation of a Wireless SAW–Pirani Sensor with Extended Range and Sensitivity

“…The equilibrium equation can be expressed as [3] P=T−T0Gr+Gc+Ggp where P is the heating power supplied to the sensor, T is the equilibrium temperature, T0 is the initial temperature, Gr is the radiative thermal conductance, Gc is the solid thermal conductance of the sensor’s carrier, and Gg is the gas conductance. Gr=εσT4−T04AT−T0 where ε is the emissivity of the sensor exterior surface, σ is the Stefan–Boltzmann constant, and A is the sensor’s emitting surface.…”

“…In the case where the sensor is suspended by one cylindrical wire, the solid conductance can be expressed as [4] Gc=λπ⋅r2l where λ is the thermal conductivity of the wire material, r is the radius of the wire, and l is the length of the wire. The gas conductance is expressed as follows [3]:Ggp=λp,hAh, with λfalse(p,hfalse) the thermal conductivity of the gas at pressure p, and A the sensor’s surface. λp,h=λp01+2⋅2−al¯pa⋅h9.56−1, where λfalse(p0false) represents the thermal conductivity of the gas at atmospheric pressure, a is the energy accommodation coefficient of the gas ...…”

The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments

“…Because the MOMA MS operates at fundamentally higher pressures than heritage QMS instruments, a micropirani pressure gauge (based on a commercial Heimann transducer) was qualified for the ExoMars mission. This device, defined by two temperature- and pressure-sensitive resistors contained within shared silicon housing, operates at pressures ranging from 10 0 to 10 −6 torr and consumes on the order of ∼0.5 mW (Völklein et al , 2013 ). Although the response time of the gauge is limited by its heat capacity, which dictates the time required for the resistors to reach equilibrium, a physics-based algorithm enables the sensor to accurately predict pressures under dynamic conditions associated with LDMS operation at Mars ambient pressures.…”

Highly Sensitive Diode-Based Micro-Pirani Vacuum Sensor with Low Power Consumption

“…Another important method is micro-hotplate (MHP) technology, for which the sensitivity of a micro-Pirani vacuum sensor has reached 230 μV/Pa (0.02 V/W/Pa) in the vacuum pressure range of 1–10 2 Pa with power consumption of 4900 μW [19]. Previous works have made great contributions to the development of micro-Pirani vacuum sensors, especially regarding theoretical analysis and structural design [20,21,22]. However, for complex sensor systems, the power consumption of a single micro-Pirani vacuum sensor is still too high and needs to be reduced, especially for battery-powered sensor systems.…”