Doekle Reinder Yntema

A four particle velocity sensor device

A thermoelectric cooling apparatus includes a plurality of thermoelectric coolers each having a hot side and a cold side. The cold sides of the thermoelectric coolers are arranged to cool an object. The hot sides of the thermoelectric coolers are provided with a heat sink. The heat sink may include a eutectic material which maintains the hot sides of the thermoelectric coolers at a low temperature so that the cold sides of the thermoelectric coolers are able to maintain the object at a cold temperature. The heat sink may have fins for rejecting heat, and air moving means for moving air over the fins to aid in the rejection of heat from the hot sides of the thermoelectric coolers. The fins may be cooled by the eutectic material.

Fully integrated three dimensional sound intensity sensor

For the first time, a complete 3-dimensional sound intensity sensor - consisting of 4 particle velocity sensors and a pressure microphone - has been integrated on a single chip, providing the possibility to do nearly point measurements of acoustic particle velocity, sound pressure, and therefore sound intensity. Principally the sensor consists of two distinct designs; a pressure sensor and particle velocity sensors. In this paper the design of the sensor, fabrication and measurement results are discussed and compared with theoretical results.

A complete three-dimensional sound intensity sensor integrated on a single chip

Complete characterization of a sound field requires measurement of both sound pressure and particle velocity. In this paper, we present a three-dimensional acoustic particle velocity sensor chip. Furthermore, a sound pressure sensor was integrated on the same chip, enabling three-dimensional sound intensity measurements. The integration of multiple sensors on a single silicon chip results in highly reproducible sensors and a very small sensor-to-sensor distance allowing for accurate single-point measurements. The latter is demonstrated by measurement of the 3D particle velocity field of a very small (1 × 1 mm2) sound source.

Analysis of the performance of a particle velocity sensor between two cylindrical obstructions

The performance of an acoustic particle velocity sensor that is placed between two cylindrical objects has been analyzed both analytically and by means of finite volume simulations on fluid dynamics. The results are compared with acoustic experiments that show a large magnification of the output signal of the particle velocity sensor due to the mounting of the sensor between two cylinders. The influences of this construction consist of an attenuation of particle velocities at frequencies below a few hertz, whereas signals in the higher frequency range are amplified, up to approximately three times (10 dB) in a frequency range between 50 and 1000 Hz. The theoretical analysis is based on the derivation of the stream function for the situation of two long cylinders immersed in an oscillating incompressible viscous fluid, at low Reynolds numbers. The results lead to an improved insight into the effects of viscosity and fluid flow that play a role in acoustic measurements and open the way for further optimization of the sensitivity of the sensor.

Integrated 3D sound intensity sensor with four-wire particle velocity sensors

A new symmetrical four-wire sensor configuration has resulted in a fully integrated sound intensity sensor with significant lower noise floor and smaller size than its predecessors. An integrated sound pressure sensor was further miniaturized by using a folded ldquoback chamberpsila at both sides of the chip.

A Microflown based sound pressure microphone suitable for harsh environments

There are several cases where a sound field reconstruction or prediction is required under harsh conditions such as high temperature, humidity or chemical attack. A regular pressure microphone will not last long under these conditions. Electret based pressure microphones stop working well above 70 degrees centigrade and other type of pressure microphones often operate with a built in amplifier that does not function above 120 degrees centigrade. The functionality of a MEMS based Microflown acoustic particle velocity sensor in air lies in the use of two heated platinum wires that are resistant to high temperatures and chemical attack. The wires are supported by silicon that has no other function than provide support. A pressure microphone is made based upon the Microflown principle by putting it in the opening of an enclosure. In this paper a silicon and platinum based sound probe for harsh environments is created, combining particle velocity and pressure measurements in a harsh environment. Use of this sensor is possible up to 250 degrees centigrade, in humid and under most chemical environments. The probe realization as well as calibration measurements are presented.

An integrated 3D sound intensity sensor using four-wire particle velocity sensors: I. Design and characterization

Complete characterization of a sound field requires measurement of both sound pressure and particle velocity. In this paper, a new symmetrical four-wire sensor configuration is discussed which has a lower noise floor than its two-wire version and measures in two dimensions. With a pair of four-wire sensors, a fully integrated 3D particle velocity sensor is realized with smaller size than its predecessors. In this paper, a further investigation towards the directivity pattern of the sensor is done, revealing that a deviation is present between the expected and measured direction. Measurements of the directionality and possible solutions to the problem are presented in this first part, whereas the second part of this paper presents a more theoretical model of the deviation. Furthermore, a connection method is discussed enabling the use of the sensor for commercial purposes and measurements are presented showing the difference in performance resulting between a two-wire and a four-wire sensor configuration.

Characterization of bio-inspired hair flow sensors for oscillatory airflows: techniques to measure the response for both flow and pressure

Hair sensors for oscillatory airflow, operating in the regime of bulk flow, particle velocity or both, can be characterized by several methods. In this work, we discuss harmonic measurements on MEMS hair flow sensors. To characterize this type of flow sensor the use of three different types of oscillatory airflow source is investigated. A loudspeaker, a vibrating sphere and a standing wave tube all have specific characteristics regarding their acoustic field, frequency range, maximum velocity amplitude and the possibility to chose the ratio between pressure and flow velocity. They are compared and an overview is given with respect to which source is the most appropriate under specific conditions. Furthermore, by combining information from the flow setups used new insights into sensor operation can be gained.

Analysis of the angular sensitivity of an innovative particle velocity sensor

In this paper a novel micromachined acoustic sensor consisting of four heated wires is analyzed theoretically and experimentally. The presence of the chip surface of the probe in the vicinity of the wires influences the local fluid flow, while it also affects the temperature distribution in the probe by altering the direction of heat transport. Both effects result into a specific angular dependence of the sensor sensitivity. To explain this specific directionality of the sensitivity, an analytical model is presented that describes both the air flow around the probe and the temperature profile around the heated wires. Acoustic flow measurements on the probe sensitivity are compared with the theory and with numerical simulations on the device, showing good qualitative and quantitative correspondence.