Abstract: A high-frequency dynamic pressure transducer calibration system and method is provided. The method directs a source onto a diaphragm of a dynamic pressure transducer. An oscillating voltage at a target frequency (or range of frequencies) is generated. The oscillating voltage is coupled to an electrical connector of the dynamic pressure transducer. A deflection pattern of the diaphragm is recorded. The dynamic pressure transducer is calibrated by correlating magnitude of the deflection pattern with the oscillating voltage as a function of the target frequency (or range of frequencies).

Abstract: Disclosed are a system and methods for calibrating wall shear stress sensors. The system includes an oscillating plate coupled to an actuator and mounted on a rolling elements, and one or more sensors coupled to a height adjusting device. The system can further comprise a height control rod coupled to a height control base and a sensor holder configured to house the one or more sensors and supported on a connector, the connector configured to be rotatably disposed about the height control rod. The system can be calibrated by causing the actuator to oscillate the oscillating plate at a frequency, sensing, using the one or more sensors, shear stress at a wall, the shear stress at the wall being associated with a velocity field, and determining a theoretical wall shear stress based on fluid properties, the frequency, and the height of the one or more sensors above the oscillating plate.

Abstract: Systems, methods, and apparatuses for taking pressure measurements are provided. A multi-hole pressure sensor probe can include a probe tip having a plurality of probe tip holes. The probe tip holes can lead to probe tip channels that convey fluid from the measurement environment to pressure transducers. The pressure transducers can operate using optical transduction techniques. A light source can be applied to the diaphragm, and the light reflected from the diaphragm changes as the position of the diaphragm changes. Further, a reflective material can be applied on the backside of the diaphragm to increase its reflective properties. The light can then be collected and analyzed using a photodiode to determine the environmental pressure acting on the different holes of the probe.

Abstract: A high-frequency dynamic pressure transducer calibration system and method is provided. The method directs a source onto a diaphragm of a dynamic pressure transducer. An oscillating voltage at a target frequency (or range of frequencies) is generated. The oscillating voltage is coupled to an electrical connector of the dynamic pressure transducer. A deflection pattern of the diaphragm is recorded. The dynamic pressure transducer is calibrated by correlating magnitude of the deflection pattern with the oscillating voltage as a function of the target frequency (or range of frequencies).

Abstract: Disclosed are a system and methods for calibrating wall shear stress sensors. The system includes an oscillating plate coupled to an actuator and mounted on a rolling elements, and one or more sensors coupled to a height adjusting device. The system can further comprise a height control rod coupled to a height control base and a sensor holder configured to house the one or more sensors and supported on a connector, the connector configured to be rotatably disposed about the height control rod. The system can be calibrated by causing the actuator to oscillate the oscillating plate at a frequency, sensing, using the one or more sensors, shear stress at a wall, the shear stress at the wall being associated with a velocity field, and determining a theoretical wall shear stress based on fluid properties, the frequency, and the height of the one or more sensors above the oscillating plate.

Abstract: A sensor system comprising a Micro-Electro-Mechanical Systems (MEMS)-based capacitive floating element shear stress sensor, the associated packaging, and the interface circuitry required for operation as an instrumentation-grade sensing system is disclosed herein. One implementation of the interface circuitry is an analog synchronous modulation/demodulation scheme enabling time-resolved measurements of both mean and dynamic wall shear stress events, where a modulation section couples to the sensor for sensing wall shear stress at the surface of an object in a fluid and generates at least one bias signal from the sensor output signal. In response to the bias signal, a demodulation control circuit adjusts the phase of the bias signal and generates a demodulation control signal from the phase adjusted signal. Consequently, in response to the demodulation control signal, a demodulation section synchronizes the rectification of the sensor output signal, while the phase information is maintained.

Abstract: Systems, methods, and apparatuses for taking pressure measurements are provided. A multi-hole pressure sensor probe can include a probe tip having a plurality of probe tip holes. The probe tip holes can lead to probe tip channels that convey fluid from the measurement environment to pressure transducers. The pressure transducers can operate using optical transduction techniques. A light source can be applied to the diaphragm, and the light reflected from the diaphragm changes as the position of the diaphragm changes. Further, a reflective material can be applied on the backside of the diaphragm to increase its reflective properties. The light can then be collected and analyzed using a photodiode to determine the environmental pressure acting on the different holes of the probe.

Abstract: Methods and apparatuses for measuring static and dynamic pressures in harsh environments are disclosed. A pressure sensor according to one embodiment of the present invention may include a diaphragm constructed from materials designed to operate in harsh environments. A waveguide may be operably connected to the diaphragm, and an electromagnetic wave producing and receiving (e.g., sensing) device may be attached to the waveguide, opposite the diaphragm. A handle may be connected between the diaphragm and the waveguide to provide both structural support and electrical functionality for the sensor. A gap may be included between the handle and the diaphragm, allowing the diaphragm to move freely. An antenna and a ground plane may be formed on the diaphragm or the handle. Electromagnetic waves may be reflected off the antenna and detected to directly measure static and dynamic pressures applied to the diaphragm.

Abstract: Flush mount sensor packages and packaging methods for micromachined transducers, which can be used for fluid flow measurements, are provided. A sensor package can include a substrate, a sensor mounted on a front side of the substrate, a wire bond coupled to the sensor and passing through the substrate, and a shim cap positioned around the sensor. The wire bond does not protrude above the topside of the sensor, and the shim cap and the sensor can be substantially flush.

Abstract: Microelectromechanical systems (MEMS)-based devices capable of measuring wall shear stress vectors in three-dimensional aerodynamic flow fields are provided. A device can include a sensor that senses wall shear stress vectors in two in-plane axes and an interface circuit including a modulation section and a demodulation section. The device can be capable of making direct, real-time wall shear stress measurements without any need for using secondary measurements and/or models for validation.

Abstract: Flush mount sensor packages and packaging methods for micromachined transducers, which can be used for fluid flow measurements, are provided. A sensor package can include a substrate, a sensor mounted on a front side of the substrate, a wire bond coupled to the sensor and passing through the substrate, and a shim cap positioned around the sensor. The wire bond does not protrude above the topside of the sensor, and the shim cap and the sensor can be substantially flush.

Abstract: Methods and apparatuses for measuring static and dynamic pressures in harsh environments are disclosed. A pressure sensor according to one embodiment of the present invention may include a diaphragm constructed from materials designed to operate in harsh environments. A waveguide may be operably connected to the diaphragm, and an electromagnetic wave producing and receiving (e.g., sensing) device may be attached to the waveguide, opposite the diaphragm. A handle may be connected between the diaphragm and the waveguide to provide both structural support and electrical functionality for the sensor. A gap may be included between the handle and the diaphragm, allowing the diaphragm to move freely. An antenna and a ground plane may be formed on the diaphragm or the handle. Electromagnetic waves may be reflected off the antenna and detected to directly measure static and dynamic pressures applied to the diaphragm.

Abstract: Microelectromechanical systems (MEMS)-based devices capable of measuring wall shear stress vectors in three-dimensional aerodynamic flow fields are provided. A device can include a sensor that senses wall shear stress vectors in two in-plane axes and an interface circuit including a modulation section and a demodulation section. The device can be capable of making direct, real-time wall shear stress measurements without any need for using secondary measurements and/or models for validation.

Abstract: A sensor system comprising a Micro-Electro-Mechanical Systems (MEMS)-based capacitive floating element shear stress sensor, the associated packaging, and the interface circuitry required for operation as an instrumentation-grade sensing system is disclosed herein. One implementation of the interface circuitry is an analog synchronous modulation/demodulation scheme enabling time-resolved measurements of both mean and dynamic wall shear stress events, where a modulation section couples to the sensor for sensing wall shear stress at the surface of an object in a fluid and generates at least one bias signal from the sensor output signal. In response to the bias signal, a demodulation control circuit adjusts the phase of the bias signal and generates a demodulation control signal from the phase adjusted signal. Consequently, in response to the demodulation control signal, a demodulation section synchronizes the rectification of the sensor output signal, while the phase information is maintained.

Abstract: A capacitive microphone and method of fabricating the same are provided. One or more holes can be formed in a first printed circuit board (PCB). A diaphragm can be surface micromachined onto an interior surface of the first PCB at a region having the one or more holes. Interface electronics can also be interconnected to the interior surface of the PCB. One or more spacer PCBs can be attached to a second PCB to the first PCB, such that appropriate interconnections between interconnect vias are made. The second PCB and first PCB with spacers in between can be attached so as to create a cavity in which the diaphragm and interface electronics are located.

Abstract: A capacitive microphone and method of fabricating the same are provided. One or more holes can be formed in a first printed circuit board (PCB). A diaphragm can be surface micro-machined onto an interior surface of the first PCB at a region having the one or more holes. Interface electronics can also be interconnected to the interior surface of the PCB. One or more spacer PCBs can be attached to a second PCB to the first PCB, such that appropriate interconnections between interconnect vias are made. The second PCB and first PCB with spacers in between can be attached so as to create a cavity in which the diaphragm and interface electronics are located.

Abstract: A capacitive microphone and method of fabricating the same are provided. One or more holes can be formed in a first printed circuit board (PCB). A diaphragm can be surface micro-machined onto an interior surface of the first PCB at a region having the one or more holes. Interface electronics can also be interconnected to the interior surface of the PCB. One or more spacer PCBs can be attached to a second PCB to the first PCB, such that appropriate interconnections between interconnect vias are made. The second PCB and first PCB with spacers in between can be attached so as to create a cavity in which the diaphragm and interface electronics are located.

Abstract: A micro-sensor package is provided that includes a micro-sensor and printed circuit board (PCB), or that includes an array of micro-sensors and PCB. The micro-sensor includes a first substrate having opposing front and back surfaces, a sensing element on the front surface of the first substrate, and a through-chip via disposed within the first substrate and electrically connected to the sensing element. The PCB includes a second substrate to which the back surface of the first substrate is bonded. The second substrate defines a recess within which a bond pad is disposed, and the through-chip via of the micro-sensor is electrically connected to the bond pad of the PCB. The micro-sensor package may further include a shim bonded to the PCB, and that may surround an outer boundary of the micro-sensor and have approximately the same thickness as the micro-sensor.

Abstract: A shear-stress sensing system can include a floating element whose displacement can be detected through use of optical measurements. The system can utilize high temperature materials to deliver the optical signal to the structure to be measured, which can also utilize high temperature materials. In one embodiment, an intensity modulation or phase modulation of a reflected signal can be measured to determine the shear stress. In another embodiment, a Moire fringe pattern can be used to determine the shear stress.

Abstract: A floating element shear sensor and method for fabricating the same are provided. According to an embodiment, a microelectromechanical systems (MEMS)-based capacitive floating element shear stress sensor is provided that can achieve time-resolved turbulence measurement. In one embodiment, a differential capacitive transduction scheme is used for shear stress measurement. The floating element structure for the differential capacitive transduction scheme incorporates inter digitated comb fingers forming differential capacitors, which provide electrical output proportional to the floating element deflection.