WO2007014400A2 - Three dimensional anemometer comprising thick film segmented thermistors - Google Patents

Three dimensional anemometer comprising thick film segmented thermistors Download PDF

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Publication number
WO2007014400A2
WO2007014400A2 PCT/YU2006/000015 YU2006000015W WO2007014400A2 WO 2007014400 A2 WO2007014400 A2 WO 2007014400A2 YU 2006000015 W YU2006000015 W YU 2006000015W WO 2007014400 A2 WO2007014400 A2 WO 2007014400A2
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Prior art keywords
temperature
wind
sensor
segmented
thermistors
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PCT/YU2006/000015
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French (fr)
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WO2007014400A3 (en
Inventor
Obrad Aleksic
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Center For Multidisciplinary Studies Of The Belgrade University
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Publication of WO2007014400A3 publication Critical patent/WO2007014400A3/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01W—METEOROLOGY
    • G01W1/00—Meteorology
    • G01W1/02—Instruments for indicating weather conditions by measuring two or more variables, e.g. humidity, pressure, temperature, cloud cover or wind speed
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K3/00—Thermometers giving results other than momentary value of temperature
    • G01K3/08—Thermometers giving results other than momentary value of temperature giving differences of values; giving differentiated values
    • G01K3/14—Thermometers giving results other than momentary value of temperature giving differences of values; giving differentiated values in respect of space
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P13/00—Indicating or recording presence, absence, or direction, of movement
    • G01P13/02—Indicating direction only, e.g. by weather vane
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P13/00—Indicating or recording presence, absence, or direction, of movement
    • G01P13/02—Indicating direction only, e.g. by weather vane
    • G01P13/04—Indicating positive or negative direction of a linear movement or clockwise or anti-clockwise direction of a rotational movement
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
    • G01P5/10—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring thermal variables
    • G01P5/12—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring thermal variables using variation of resistance of a heated conductor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01W—METEOROLOGY
    • G01W1/00—Meteorology
    • G01W1/17—Catathermometers for measuring "cooling value" related either to weather conditions or to comfort of other human environment
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Definitions

  • the invention belongs to the field of sensors, which measure non-electrical properties using electrical measurements. It belongs to meteorological sensors because it measures the speed of wind, humidity and temperature of air. In the classification of materials it belongs to low temperature thermistors based on metal oxide semiconductors. In the classification of manufacturing technologies it belongs to thick film sensors. In the international patent classification it belongs to: G Ol P5/ 01 and G 01 P13 / 00.
  • the invention solves measuring of the vector of wind speed by sensors and electronics, without moving parts, in the x, y, z- coordinate system oriented under a compass or in a spherical coordinate system, under different climatic conditions including rain, snow, ice-rain and ice shower, immediately defines by electronic means data of speed intensity and direction on each axes or angles in the spherical coordinate system, and gives temperature and humidity data, showing the start or end of rainfalls.
  • This sensor system that occupies a few dm 3 of space provides more accurate measuring of the vector of wind speed using self - heated thick film segmented thermistors and takes account of the influence of the air temperature and humidity. It also provides continual and autonomous measuring without monitoring person presence, data remote control and transfer, intelligent PC data processing.
  • Wind speed meters-anemometers are produced today in a variety of shapes. Generally they could be divided in two groups: electro-mechanical and electro-resistive.
  • the first group of anemometers electro-mechanical has a small propeller arround 5 cm in diameter making revolutions caused by wind blowing. Friction in the bearings is very small, the propeller speed (number of revolutions) is measured optically, electro-magnetically or using a Hall probe. They could be hand sized, have a digital display, send data by a mobile phone or hand transmitter unit. The wind speed is measured integrally. Inaccuracy of measurement is arround 5 %. Temperature thermistor disc sensors could be built in a hand unit. Usually they are not used below -10 0 C because of consumer electronics and battery instabilities.
  • the second group of anemometers has a Pt resistor with a positive temperature coefficient (PTC), disc thermistors or thin miniaturized semiconducting sensors with a negative temperature coefficient (NTC).
  • PTC positive temperature coefficient
  • NTC negative temperature coefficient
  • Heated electro-resistive sensors have a self-temperature of at least 30-50 degrees higher than the air flowing mat cools them and increases resistivity. If the voltage supply is constant, the current is decreasing in that case.
  • a dual pivoting vane having a miniature dual bead thermistor anemometer at its upstream extremity and with light beam angular position sensors on the pivot axes provides a sensitive velocity vector sensor for measuring both magnitude and
  • the present invention is a heated element sensor for detecting the flow rate of the fluid or outer physical characteristics of a fluid.
  • the invention teaches driving the thermo-resistive element along a profile having at least two states and measuring the power and temperature of the sensor at each state. In this way a dissipation coefficient can be determined and fluid flow and outer physical characteristics 100 determined without the need for ambient temperature to be defined.
  • the method and apparatus include a bridge circuit configured to develop a bridge voltage Vb such that the magnitude of the bridge voltage Vb is indicative of the amount of flow.
  • the bridge circuit is configured without having an ambient temperature sensor, thus the bridge voltage is uncompensated with respect to ambient temperature.
  • a thermistor circuit is configured to generate a temperature reference
  • a conditioning circuit is configured to receive the uncompensated bridge voltage and the temperature reference voltage to process the same and generate a compensated bridge voltage with respect to ambient temperature.
  • the compensated bridge voltage is indicative of fluid flow.
  • An airflow sensor formed on a silicon chip comprises a silicon base covered with an insulating polyamide layer, a lineal resistance heater on the chip energized with current pulses to propagate thermal waves, and a thermistor on the chip
  • Circuitry determines flow rate as a function of the measured propagation time of the thermal wave.
  • the thermistor may be replaced by a bridge of four resistive elements of which only one or two are sensitive to the thermal wave.
  • the thermistor material is platinum, polycrystalline silicon or amorphous silicon, which exhibit high
  • Such a device has specific application in an optical air pollution monitor to give a continuous indication of a fluid flow thus ensuring that the monitor is sampling fresh batches of fluid from a monitored space.
  • a flow sensor comprising a pair of thin film heat sensors and thin film heater is disclosed.
  • the flow sensor further comprises a semiconductive body with a depression therein and structure connecting the heater and the sensors to the body and
  • the structure connecting comprising two thin films members bridging the depression, each member comprising one sensor and portion of the heater.
  • An illustrative embodiment includes a microphone positioned to engage wind pressure from a first relative direction and a controller coupled to receive an audio signal from the microphone.
  • the controller
  • 155 compares the audio signal with plural threshold values, representative of wind pressure levels, and determines a first wind pressure level incident upon the microphone. Filtering and gain controls are used to condition the audio signal output from the microphone. Plural microphones are employed to allow that detection of wind direction and magnitude about a compass of directions. Digital signal
  • the wind direction and magnitude data are used to recommend a golf club size adjustment and a golf swing direction adjustment to the user, who has taken a measurement of the wind with respect to reference golf swing direction.
  • a temperature sensor is added and controller calculates a wind chill factor.
  • sensor temperature is determined by sampled measurement of its resistance.
  • Sensor temperature is controlled by varying the voltage applied to the sensor with an error value determined by the difference between actual sensor resistance and the desired resistance.
  • the probe sensing elements are a selfheated thermistor and solid state temperature sensing device, that are separately but simultaneously exposed in use of the instrument, to the air flow, with the energy
  • the solid state temperature sensing device is a temperature sensing transistor, and develops a signal that is proportional to the air stream temperature. Two signals are
  • thermal type flow meter for measuring the mass flow rate of a fluid medium especially that of a gas in a duct, said meter comprising a plurality of thermistors operated electrically in the "self-heated" mode located on the trailing edge of rigid, rectangular members oriented with the long axis perpendicular to the
  • the thermistors are located strategically throughout transverse plan of the duct. Each sensor (thermistor) is located substantially at the center of the downstream end of right circular cylinder. The voltage drops through all of the thermistors located in a two dimensional array oriented normal to the flow direction and summed electrically using an operational amplifier. Due to both the
  • the voltage drop across each sensor is linearly proportional to the local mass flow velocity. This allows the summed output from all of the flow dependent sensors to represent a true average of the flow in a duct providing a sufficient number of sensors exist to reveal the overall flow patterns in the duct.
  • An apparatus comprises a sensor including a heater, an upstream detector 220 and downstream detector.
  • An AC signal source excites the heater to generate propagating heat signals that are received by the upstream and downstream detectors.
  • a first detecting circuit provides a first output signal responsive to the propagating heat signals received by the first detector and second detecting circuit provides a second output signal responsive to the propagating heat signals received by 225 downstream detector.
  • a difference circuit subtracts the first and second signals to obtain a difference signal and an output circuit provides an output signal responsive to the difference signal, which reflects both magnitude and phase. The resulting output signal has improved resolution and provides for improved sensor stability.
  • a system for measuring the flow rate of gas includes a flow head having a sensor thermo resistor mounted transversely to the flow of gas, and a reference thermoresistor mounted parallel to the flow of gas, both thermoresitors having equal
  • thermoresistor is connected in a feedback control circuit, in which each thermoresistor is separately supplied with current to heat it, the current first passing through a fixed resistance in series with each of thermoresistors.
  • the current supplies are servo controlled to equalize the resistance of each thermoresistor with that of its associated fixed resistance.
  • thermoresistor 240 power consumed by each thermoresistor at its equilibrium resistance is measured to provide a power indicative signal associated with each thermoresistor.
  • the two power indicative signals are compared to generate a delta power signal.
  • An empirically - derived flow rate versus delta power curve is stored as a look up table in a computer memory. The value of delta power signal is supplied to address the look -up table to
  • the flow meter 250 having a laser Doppler anemometer (LDA) which measures instantaneous center line velocity of fluid flow in a pipe.
  • LDA laser Doppler anemometer
  • the flow meter may process the instantaneous velocity so obtained to compute the volumetric flow rate , mass rate, and /or other flow characteristics (e.g., as instantaneous quantities and/or integrated over a time interval).
  • the flow meter may use an electronic processing method.
  • processing method may provide essentially an exact solution to the Navier-Stokes equations for any periodically oscillating flow.
  • a disk probe veloci meter is formed by multiple orthogonal disks fitted with pressure transducers positioned to measure dynamic pressure differences between the center of one disk face and the center of the other face on each disk.
  • the velocimeter can measure reasonably accurately three component of velocity where the approximate direction of the flow is not known. Where the dominant velocity component is known the velocimeter may be combined with a Pitot probe to 265 form a compact anemometer.
  • the proposed flow rate meter based on a heat loss anemometer contains thermistor temperature transducers , resistors, an alternating current amplifier , a phase detector, a null comparator, a control unit, a square pulse generator, a voltage regulator, a switch, a high-frequency timing pulse generator, and additionally a main oscillator and bus former.
  • the first output of the main oscillator is connected to the
  • the second output is connected to the corresponding input of the square pulse generator, and the input connected to the corresponding output of the voltage regulator.
  • the input of the bus former is connected to the output of the switch.
  • the thermistor temperature transducers are arranged in the planes that are perpendicular to the longitudinal axis of the monitored
  • Ultrasonic anemometer for measurement of wind speed has an improved phase measurement procedure to provide more accurate wind velocity measurements
  • the measurement procedure is based on measuring signal transit time by measuring its phase shift.
  • Each of the received signal phases is determined by counting from a delay point of the emission signal, calibrated to center the phase capture on within a signal period.
  • the delay is checked by the action of a thermistor placed in the device body to maintain temperature in the center of its range.
  • an ultrasonic anemometer device that comprises 4 electro- acoustic transducers mounted above a space in which the air flow is to be measured and a wave reflector.
  • the reflector has a porous surface favoring removal of humidity deposits.
  • the temperature-compensated constant temperature anemometer permits directionally independent and low-noise measurement of low air speed by means of NTC thermistors arranged in the bridge. Because of the small dimensions, the anemometer is practically suitable for boundary layer measurements. This is achieved 310 by particular selection of the different combination of characteristics for the voltage/current characteristic, resistance values, resistance/temperature characteristics of the measuring and compensating NTC thermistor.
  • a three dimensional anemometer configured of segmented thermistors measures the wind speed vector, gives values of projections of the wind speed vector on the space coordinate axes, shows wind speed directions both in x, y, z rectangular coordinate system and sphere coordinate system at different modest climate continental
  • a three-dimensional anemometer comprising of segmented thermistors consists of 5 sensors: three of them measure the wind speed on x, y, z —axes (placed perpendicularly one to another in the compass direction), one additional sensor is used for the air temperature measurement and one is an additional humidity sensor.
  • a three-dimensional anemometer ( Figure 1) operates on a heat loss principle of self- heated thermistors placed in the enclosures opened to air flow (wind).
  • a three- dimensional anemometer is configured as a system of 5 sensors comprising all together of 6 thick film segmented NTC thermistors equal in shape and values of
  • NTC thermistor placed along the enclosure in the airflow direction ( Figure 2).
  • Segmented NTC thermistor are powered by a constant voltage supply, and are heated by variable self-current. They are warmer in comparison to ambient air for 30- 50 0 C.
  • NTC thermistor current decreases when the wind speed increases, because thermistors are partly cooled in that moment.
  • NTC thermistor resistivity increases by cooling of the thermistor.
  • Its resistivity is measured by measuring the self-current — self-heated current of the thermistor, which changes proportionally to the wind speed, but at constant voltage supply.
  • a 10 ⁇ stable resistor is added serially to the thermistor for measuring the voltage drop and the current is calculated by dividing the measured voltage by 10 ⁇ .
  • the maximum of thermistor current is limited to 100 mA with a current protection circuit.
  • the momentary temperature on the thermistor is determined by measuring the thermistor resistivity.
  • the momentary thermistor power is then determined by the parameters mentioned above. In that way calibration curves are derived serving for direct determination of wind speed for each resistivity value or thermistor current I t h measured.
  • a constant current supply method (constant self-heating) of segmented thermistors can be performed.
  • a thermistor voltage varies with cooling caused by airflow e.g., wind blowing on a certain axis.
  • Calibration curves of wind speed are then a function of voltage U th measured on the thermistor.
  • Calibration curves for example thermistor current change vs. wind speed, in a certain quantity are dependent on the air temperature and humidity. Therefore two additional sensors were configured in the measuring anemometer system: temperature sensor (marked by T in Figure 1) and humidity sensor (marked by H in figure 1).
  • the thermistor measuring the air temperature T ( Figure 5) is not self-heated by a constant current and operates independently. It is in direct contact with air and its resistivity is a function of the air temperature.
  • the humidity sensor H (figure 6) has two equal thick film segmented thermistors marked by (1) and (2) that- are placed in a Wheatstone bridge. Both of them are heated by self-currents through them after constant voltage supply: one is compensative and another is active.
  • a current difference between compensative (2) and active (1) thermistors increases with an increase of humidity; in that way humidity vs. bridge output voltage is calibrated after air temperature is measured.
  • Thermistors are placed in the differential branches of the Wheatstone bridge, linearized and balanced prior to use: humidity changes are measured as a function of the bridge output voltage.
  • the humidity sensor is dependant on the air temperature in its operation. Using data of the air temperature from sensor T and humidity data from sensor H certain corresponding calibration curves for the wind speed on the x, y, z - axes are selected after the temperature and humidity are measured. The wind speed is determined by reading a value on a calibration curve.
  • the wind direction is determined by a temperature gradient on a segmented thermistor. Without a wind blowing, the supply voltage is nearly equally distributed over a segmented thermistor. When air is flowing through the sensors placed on x, y, z, -axes the equal distribution is changed. Half of the thermistor that is positioned closest to the airflow
  • the airflow (wind) has a direction from the colder to warmer part of a thermistor e.g. from higher to lower resistivity or measuring the voltage from higher to lower voltage. This voltage difference is measured on inner electrodes of a segmented thermistor marked
  • the wind speed and direction is determined on each axis x, y, or z and the total intensity is calculated as a vector modulus.
  • the airflow direction - wind direction on a certain axis gives a sign
  • the angles in relation to the x, y, z coordinate system, that the wind speed vector makes are determined from the vector self projections to the axes and vector modulus.
  • the wind speed vector projections are measured previously as intensities of the wind speed vector decomposed to the axes.
  • Transition from the x, y, z- axes coordinate system to a spherical coordinate system is defined in trigonometry.
  • Calibration curve selection, speed modulus calculation, determination of direction and angles, trigonometry formulae, polynomials for interpolation and measured responses recording of all sensors e.g. the total data processing for all sensors in the system is performed on a personal
  • Possibility of rainfall is staled first by a humidity sensor as an overcritical humidity. Then a vertical wind speed is monitored by a wind speed sensor placed along the z-axis (sensor response to rainfall is measured). In the moment of rainfall fast cooling of segmented thermistor starts, that is equal to a fast and extremely high
  • Thick film segmented thermistor has an alumina substrate as a sensor. PdAg electrodes are placed in two rows e.g. alternately in a zigzag order.
  • the thermistor paste was composed of thermistor powder (based on Mn, Ni, Co, Fe. -oxide mixture), an organic vehicle and glass frit. It was screen printed on alumina, dryed and sintered at 850 0 C.
  • An UI characteristic e.g. resistivity of a pair of segmented thermistors as a function of temperature is given in Figure 10.
  • the total resistivity of a thermistor is a sum of resistivity of segments.
  • the voltage supply is equally distributed over segments in the absence of wind or airflow.
  • a segmented thermistor has a large
  • surface value opened for heat transfer. It can be used for temperature gradient measurements (inner electrodes) or determination of the airflow direction. It measures temperature integrally (outer electrodes) or partially e.g. differentially on segments. It can be trimmed abrasively by a long edge L- cut to tolerances as small as 0.1 ⁇ .
  • a three dimensional anemometer configured of thick film segmented thermistors is aimed for measuring and determination of wind energy on meteorological high post locations for long term monitoring of wind speed changes and its exploiting for wind mill generators.
  • the anemometer presented above can be
  • 460 serve for direct remote control of wind energy and remote windmills adjusting to wind direction in real time.
  • NTC pastes are composed in Du Pont, ESL, Heraeus etc., and for example CMS Materials Division in Belgrade. Characterization
  • XP EXCEL and C++ for PC is a suitable tool for measuring sensor response, presenting channel (sensor) data in real 470 time, measuring time response, calculating wind speed modulus and angles, recording and presenting long term data and remote monitoring in real time.

Abstract

A three-dimensional anemometer containing thick film segmented thermistors for measuring wind speed using a heat loss method. Thick film segmented NTC thermistors are heated by their self-current under constant voltage supply. They have more segments connected in series to measure temperature in average; moreover they use internal electrodes to measure the temperature gradient and wind direction. The anemometer consists of 5 sensors: three measure wind speed on the x,y,z - axes, the fourth measures air temperature and the fifth measures humidity. The humidity sensor consists of two segmented thermistors put in Wheatstone bridge: the first is active -in contact with humidity and the second is isolated. The wind speed is obtained from calibration curves: thermistor current vs. wind speed, where temperature and humidity are parameters. The wind speed vector is obtained using projections on the axes. Then, modulo is calculated, and angles between speed vector and axes using modulo and projections on the axes. Data of 5 sensors are compared and applied using a PC for wind energy monitoring and remote control of windmill generators in real time.

Description

THREE DIMENSIONAL ANEMOMETER COMPRISING THICK FILM SEGMENTED THERMISTORS
Technical Field
The invention belongs to the field of sensors, which measure non-electrical properties using electrical measurements. It belongs to meteorological sensors because it measures the speed of wind, humidity and temperature of air. In the classification of materials it belongs to low temperature thermistors based on metal oxide semiconductors. In the classification of manufacturing technologies it belongs to thick film sensors. In the international patent classification it belongs to: G Ol P5/ 01 and G 01 P13 / 00.
The invention solves measuring of the vector of wind speed by sensors and electronics, without moving parts, in the x, y, z- coordinate system oriented under a compass or in a spherical coordinate system, under different climatic conditions including rain, snow, ice-rain and ice shower, immediately defines by electronic means data of speed intensity and direction on each axes or angles in the spherical coordinate system, and gives temperature and humidity data, showing the start or end of rainfalls. This sensor system that occupies a few dm3 of space provides more accurate measuring of the vector of wind speed using self - heated thick film segmented thermistors and takes account of the influence of the air temperature and humidity. It also provides continual and autonomous measuring without monitoring person presence, data remote control and transfer, intelligent PC data processing. Background Art
Wind speed meters-anemometers are produced today in a variety of shapes. Generally they could be divided in two groups: electro-mechanical and electro-resistive.
The first group of anemometers (electro-mechanical) has a small propeller arround 5 cm in diameter making revolutions caused by wind blowing. Friction in the bearings is very small, the propeller speed (number of revolutions) is measured optically, electro-magnetically or using a Hall probe. They could be hand sized, have a digital display, send data by a mobile phone or hand transmitter unit. The wind speed is measured integrally. Inaccuracy of measurement is arround 5 %. Temperature thermistor disc sensors could be built in a hand unit. Usually they are not used below -10 0C because of consumer electronics and battery instabilities. They are manufactured widely: Nielsen Kellerman, Kestrel, Creative Energy Technologies, Aircraft Spruce, Extech Instruments, Accu Mall etc. Professional anemometers of this type are used in meteorological measurements. A known producer of professional anemometers is also Ekopower, Vaisala. Their inaccuracy is less than 3%. [ Ref- www.vaisala.com Vaisala Products (Catalogue)m, Wind Measurement, Wind Profiling ; www.nkhome. com , Nielsen Kellerman (Catalogue), Kestrel Wind & Weather Instruments, Kestrel 1000-4000 Wind Meters, pp 1-4 ; www.ekopower.nl Ekopower (Catalogue, Wind Meters , Eko -40 Anemometer -Wind Sensor, pp 1-3; www.cetsolar.com , CET : Wind Meters for Measuring Wind, Product : SM 18 to 28 Wind Meters and 10 +MiIe FRS/GMRS Radios with Weather & Vibrating Alert (Mossy Oak Camo); www. aircraftspruce. com , Wind Meters 100 to 400; ]. www.monstermarketplace.com Wind Meters on Line (Meter Mall.com); www . acumall .com. , Accu Mall Weather Instruments, Wind Meters, TWM 271, WW- 1, etc.(Catalogue) : www .forstery-suppliers . com Forstery Suppliers Inc. , Weather Instruments ]. The second group of anemometers (electro-resistive) has a Pt resistor with a positive temperature coefficient (PTC), disc thermistors or thin miniaturized semiconducting sensors with a negative temperature coefficient (NTC). This group operates on heat loss caused by wind blowing. Heated electro-resistive sensors have a self-temperature of at least 30-50 degrees higher than the air flowing mat cools them and increases resistivity. If the voltage supply is constant, the current is decreasing in that case. They measure integrally wind speed in a certain direction. Hand units of this type of anemometers have only one measuring probe. They should be moved in different directions to find a maximum response to wind blowing as well as in the application of electro-mechanical anemometers. Usually electro-resistive anemometers measure with an inaccuracy of 5% and are not used below -10 0C, because of consumer electronics and battery instability. They apply digital electronic circuits and show a wind speed and temperature for a chosen direction on the digital display. They are widely manufactured: Extech Instruments, Digitron, Airflow, Climatronic, etc. [Ref- www.testequipmentdepot.com / extech, Extech Air Flow Vane Anemometers (Catalogue) , Product 45 118- 407 119A, Heavy Duty Hot Wire CFM Thermo- Anemometer; www.digitron.co.uk Digitron Co., Product AF 210 Anemometer; www.airflow.com TA4 Anemometer, Operating Instructions; www . climatronics . com Climatronics, Products (Sensors), Wind Speed and Direction, No 102263]. In the x-y plane three ultrasonic sensors in an equal sized triangle could be placed in order to get information about wind direction and intensity (2D anemometer, Vaisala). A humidity sensor, temperature sensor and pressure sensor is added to this system. [Ref- www.vaisala.com Vaisala Group, Product Catalogue 1998-2003, Vaisala Ultrasonic Wind Measuring Technology, Weather Multisensor System ]
A disadvantage of both groups of commercial anemometers is that wind speed measuring on the z-axis does not exist. Therefore in the mountains and on inclined plains the wind speed is measured incorrectly.
In the US Patent and EU Patents several anemometers with NTC and PTC sensors exist but they are not 3D sensors and they don't comprise of segmented thick film thermistors. US Patents contain a lot of thermistor anemometers with disc NTC and PTC thermistors or Platinum PTC sensors (resistors), thin film NTC semiconducting sensors, integrated Si- sensors and fluid flow meters for different applications but no 3D anemometers or those comprising of segmented thermistors. Lasers, ultrasonic sources and Doppler Effect, Zener diodes, platinum wire, Pitot tube, elastic membranes under wind pressures and microphones are often used for wind speed measuring.
A brief review of patents: US Patent 4, 052, 894 11. October 1977. William R. et alt. Velocity vector sensor for low speed airflows
Abstract - A dual pivoting vane having a miniature dual bead thermistor anemometer at its upstream extremity and with light beam angular position sensors on the pivot axes provides a sensitive velocity vector sensor for measuring both magnitude and
90 direction of low velocity airflow relative to three dimensional reference space of the body carrying the velocity vector sensor.
US Patent 5, 117, 691 2 June 1992. Fraser ; Allan B Heated element velocimeter
95 Abstract-The present invention is a heated element sensor for detecting the flow rate of the fluid or outer physical characteristics of a fluid. The invention teaches driving the thermo-resistive element along a profile having at least two states and measuring the power and temperature of the sensor at each state. In this way a dissipation coefficient can be determined and fluid flow and outer physical characteristics 100 determined without the need for ambient temperature to be defined.
US Patent 6, 813, 570 2 November 2004. Gee; Gregory P.
Optimized convection based mass airflow sensor circuit
Abstract- A znethod and apparatus for measuring the amount of flow of a flowing
105 medium. The method and apparatus include a bridge circuit configured to develop a bridge voltage Vb such that the magnitude of the bridge voltage Vb is indicative of the amount of flow. The bridge circuit is configured without having an ambient temperature sensor, thus the bridge voltage is uncompensated with respect to ambient temperature. A thermistor circuit is configured to generate a temperature reference
110 voltage indicative of ambient temperature. A conditioning circuit is configured to receive the uncompensated bridge voltage and the temperature reference voltage to process the same and generate a compensated bridge voltage with respect to ambient temperature. The compensated bridge voltage is indicative of fluid flow.
115 US Patent 5,243,858 14 September 1993. Erskine; James C. Fluid flow sensor with thermistor detector
Abstract- An airflow sensor formed on a silicon chip comprises a silicon base covered with an insulating polyamide layer, a lineal resistance heater on the chip energized with current pulses to propagate thermal waves, and a thermistor on the chip
120 downstream of the heater to detect the arrival of each thermal wave. Circuitry determines flow rate as a function of the measured propagation time of the thermal wave. The thermistor may be replaced by a bridge of four resistive elements of which only one or two are sensitive to the thermal wave. The thermistor material is platinum, polycrystalline silicon or amorphous silicon, which exhibit high
125 temperature coefficients of resistance.
US Patent 4, 871, 065 1 November 1988. Cole; Martin T. Solid state anemometers and temperature gauges 130 Abstract- A solid state temperature and/or anemometer measuring instrument for a fluid medium such as atmosphere the instrument including a pair of semi conductor junction means such as a Zener diode one of which is exposed to fluid flow the other being isolated and providing outputs which are a function of the temperature of the fluid and a measuring device for measuring the respective outputs the differential
135 being an indication of temperature of fluid speed. Such a device has specific application in an optical air pollution monitor to give a continuous indication of a fluid flow thus ensuring that the monitor is sampling fresh batches of fluid from a monitored space.
140 US Patent 4, 478, 077 23 October 1974. Bolirer; Philip J. Flow sensor
Abstract- A flow sensor comprising a pair of thin film heat sensors and thin film heater is disclosed. The flow sensor further comprises a semiconductive body with a depression therein and structure connecting the heater and the sensors to the body and
145 bridging the depression so that at least a major portion of the heater and the sensors are out of contact with the body. The sensors are disposed on opposite sides of the heater , the structure connecting comprising two thin films members bridging the depression, each member comprising one sensor and portion of the heater.
150 US Patent 6, 684, 174. 27. January 2004 Clark ; John M. Wind gauge
Abstract- A wind gauge apparatus and method. An illustrative embodiment includes a microphone positioned to engage wind pressure from a first relative direction and a controller coupled to receive an audio signal from the microphone. The controller
155 compares the audio signal with plural threshold values, representative of wind pressure levels, and determines a first wind pressure level incident upon the microphone. Filtering and gain controls are used to condition the audio signal output from the microphone. Plural microphones are employed to allow that detection of wind direction and magnitude about a compass of directions. Digital signal
160 processing is employed to process data. In an illustrative embodiment, the wind direction and magnitude data are used to recommend a golf club size adjustment and a golf swing direction adjustment to the user, who has taken a measurement of the wind with respect to reference golf swing direction. In another embodiment, a temperature sensor is added and controller calculates a wind chill factor.
165
US Patent 6, 905, 242 14 June 2005 Heuer; Daniel A.
Sensor temperature control in thermal anemometer
Abstract- A thermal anemometer that separates sensor heating from sensor temperature measurement through a switched sampling technique. This approach
170 demonstrates several advantages over the more typical circuitry employing a bridge, which simultaneously heats the sensor and senses the ambient and velocity sensor temperature. In a thermal anemometer in accordance with the present invention, sensor temperature is determined by sampled measurement of its resistance.. 175 Sensor temperature is controlled by varying the voltage applied to the sensor with an error value determined by the difference between actual sensor resistance and the desired resistance.
US Patent 4, 537, 068 27 August 1985 Wrobel; Stanley A
180 Thermal anemometer
Abstract- A thermal anemometer arranged to measure air velocity over a vide range of ambient temperature and velocities , and a method of measuring such air velocity free of influence of ambient temperature , in which the anemometer comprises a probe containing two separate and distinct sensing elements , and a hand held
185 electronic read out unit that contains sensing signal electronic processing circuitry, function control, and an analog read out meter, which the probe and read out unit being interconnected by a self coiling cable. The probe sensing elements are a selfheated thermistor and solid state temperature sensing device, that are separately but simultaneously exposed in use of the instrument, to the air flow, with the energy
190 consumed by the thermistor, and its resulting signal, being an indication of both the velocity of the air stream and the difference in temperature between the forced operating temperature of the thermistor and the air stream ambient temperature. The solid state temperature sensing device is a temperature sensing transistor, and develops a signal that is proportional to the air stream temperature. Two signals are
195 electronically combined at the read out unit to eliminate the effect of any ambient temperature variations, to provide an air stream velocity reading at the meter that is independent to ambient temperature.
US Patent 4,581,930. 15. April 1986. ; Komons Michael
200 Average mass flow rate meter using self - heated thermistors
Abstract- A thermal type flow meter for measuring the mass flow rate of a fluid medium especially that of a gas in a duct, said meter comprising a plurality of thermistors operated electrically in the "self-heated" mode located on the trailing edge of rigid, rectangular members oriented with the long axis perpendicular to the
205 primary direction of flow. The thermistors are located strategically throughout transverse plan of the duct. Each sensor (thermistor) is located substantially at the center of the downstream end of right circular cylinder. The voltage drops through all of the thermistors located in a two dimensional array oriented normal to the flow direction and summed electrically using an operational amplifier. Due to both the
210 geometrical location of the sensors and the characteristics of thermistors in the self- heated mode, the voltage drop across each sensor is linearly proportional to the local mass flow velocity. This allows the summed output from all of the flow dependent sensors to represent a true average of the flow in a duct providing a sufficient number of sensors exist to reveal the overall flow patterns in the duct.
215
US Patent 5, 263, 380 23 November 1993. ; Sultan Michael F. Differential AC anemometer Abstract- An apparatus comprises a sensor including a heater, an upstream detector 220 and downstream detector. An AC signal source excites the heater to generate propagating heat signals that are received by the upstream and downstream detectors. A first detecting circuit provides a first output signal responsive to the propagating heat signals received by the first detector and second detecting circuit provides a second output signal responsive to the propagating heat signals received by 225 downstream detector. A difference circuit subtracts the first and second signals to obtain a difference signal and an output circuit provides an output signal responsive to the difference signal, which reflects both magnitude and phase. The resulting output signal has improved resolution and provides for improved sensor stability.
230 US Patent 5, 460, 039 24 October 1995 Cutler; Charles W. Flow sensor system
Abstract- A system for measuring the flow rate of gas includes a flow head having a sensor thermo resistor mounted transversely to the flow of gas, and a reference thermoresistor mounted parallel to the flow of gas, both thermoresitors having equal
235 resistance versus temperature functions. Each thermoresistor is connected in a feedback control circuit, in which each thermoresistor is separately supplied with current to heat it, the current first passing through a fixed resistance in series with each of thermoresistors. The current supplies are servo controlled to equalize the resistance of each thermoresistor with that of its associated fixed resistance. The
240 power consumed by each thermoresistor at its equilibrium resistance is measured to provide a power indicative signal associated with each thermoresistor. The two power indicative signals are compared to generate a delta power signal. An empirically - derived flow rate versus delta power curve is stored as a look up table in a computer memory. The value of delta power signal is supplied to address the look -up table to
245 acquire the corresponding flow rate value.
US Patent 6, 874, 480 5. April 2005. Ismailov ; Murad M.
Flow Meter
Abstract- Various embodiments of the present invention provide a flow meter device
250 having a laser Doppler anemometer (LDA) which measures instantaneous center line velocity of fluid flow in a pipe. The flow meter may process the instantaneous velocity so obtained to compute the volumetric flow rate , mass rate, and /or other flow characteristics (e.g., as instantaneous quantities and/or integrated over a time interval).The flow meter may use an electronic processing method. The electronic
255 processing method may provide essentially an exact solution to the Navier-Stokes equations for any periodically oscillating flow.
US Patent 6, 571, 645 3. June 2003. Green ; Sheldon I. Differential pressure veloci meter with probe body having disc shape
260 Abstract - A disk probe veloci meter is formed by multiple orthogonal disks fitted with pressure transducers positioned to measure dynamic pressure differences between the center of one disk face and the center of the other face on each disk. The velocimeter can measure reasonably accurately three component of velocity where the approximate direction of the flow is not known. Where the dominant velocity component is known the velocimeter may be combined with a Pitot probe to 265 form a compact anemometer.
JP2002116220. 19. April 2002.; Inoue Norihisa
Strain-type anemometer for selection of construction location point of windmill for wind turbine generator
270 Abstract- Problem to be solved: To provide a strain-type anemometer which is suitable for observing the construction candidate point of a windmill for a wind turbine generator simultaneously in many points. Solution: In the strain type anemometer three elastic receiving plates are fixed one by one perpendicularly to respective side faces of a fixation member so as to be at right angles to each other,
275 and for each of strain gages are pasted on the respective wind receiving plates as bridge circuit which detect the wind direction and the wind velocity of a wind.
UA65258. 15. March 2004. ; Dmitryv Vasyl Tarasovych Flow rate meter based on heat loss anemometer
280 Abstract- The proposed flow rate meter based on a heat loss anemometer contains thermistor temperature transducers , resistors, an alternating current amplifier , a phase detector, a null comparator, a control unit, a square pulse generator, a voltage regulator, a switch, a high-frequency timing pulse generator, and additionally a main oscillator and bus former. The first output of the main oscillator is connected to the
285 corresponding input of the phase detector, the second output is connected to the corresponding input of the square pulse generator, and the input connected to the corresponding output of the voltage regulator. The input of the bus former is connected to the output of the switch. The thermistor temperature transducers are arranged in the planes that are perpendicular to the longitudinal axis of the monitored
290 pipeline.
FR 2800876 11. May 2001.; Lamiraux Christian
Ultrasonic anemometer for measurement of wind speed has an improved phase measurement procedure to provide more accurate wind velocity measurements
295 Abstract-The measurement procedure is based on measuring signal transit time by measuring its phase shift. Each of the received signal phases is determined by counting from a delay point of the emission signal, calibrated to center the phase capture on within a signal period. The delay is checked by the action of a thermistor placed in the device body to maintain temperature in the center of its range. The
300 invention also relates to an ultrasonic anemometer device that comprises 4 electro- acoustic transducers mounted above a space in which the air flow is to be measured and a wave reflector. The reflector has a porous surface favoring removal of humidity deposits.
305 DE 31G8021 14. October 1982.; Mayer Erhard (DD)
Abstract- The temperature-compensated constant temperature anemometer permits directionally independent and low-noise measurement of low air speed by means of NTC thermistors arranged in the bridge. Because of the small dimensions, the anemometer is practically suitable for boundary layer measurements. This is achieved 310 by particular selection of the different combination of characteristics for the voltage/current characteristic, resistance values, resistance/temperature characteristics of the measuring and compensating NTC thermistor.
Disclosure of the invention
315
A three dimensional anemometer configured of segmented thermistors measures the wind speed vector, gives values of projections of the wind speed vector on the space coordinate axes, shows wind speed directions both in x, y, z rectangular coordinate system and sphere coordinate system at different modest climate continental
320 conditions. A three-dimensional anemometer comprising of segmented thermistors consists of 5 sensors: three of them measure the wind speed on x, y, z —axes (placed perpendicularly one to another in the compass direction), one additional sensor is used for the air temperature measurement and one is an additional humidity sensor.
325 Brief description of drawings
Figure 1. Space arrangement of sensors that configure a three dimensional anemometer
- Figure 2. Cross section of the wind speed sensor for measuring one axis 330 - Figure 3. Cross section of a segmented NTC thermistor sensor
- Figure 4. Top view of a pair of segmented thermistors Figure 5. Cross section of a temperature sensor Figure 6. Cross section of a humidity sensor
- Figure 7. Block scheme of sensor connection to an acquisition card and PC 335 - Figure 8. Calibration curve of the wind speed sensor for measuring one axis
Figure 9. Time delay of the wind speed sensor response- sensor inertia
- Figure 10. UI characteristic of a segmented thermistor
Best mode for carrying out of the invention
340
A three-dimensional anemometer (Figure 1) operates on a heat loss principle of self- heated thermistors placed in the enclosures opened to air flow (wind). A three- dimensional anemometer is configured as a system of 5 sensors comprising all together of 6 thick film segmented NTC thermistors equal in shape and values of
345 room temperature resistivity. Three uniaxial wind speed sensors are placed perpendicular one to another to the x, y, z- axes (marked by X, Y, Z in Figure 1). A wind speed vector projection on an axis is measured by one segmented NTC thermistor placed along the enclosure in the airflow direction (Figure 2). Segmented NTC thermistors are powered by a constant voltage supply, and are heated by variable self-current. They are warmer in comparison to ambient air for 30- 50 0C. NTC thermistor current decreases when the wind speed increases, because thermistors are partly cooled in that moment. NTC thermistor resistivity increases by cooling of the thermistor. Its resistivity is measured by measuring the self-current — self-heated current of the thermistor, which changes proportionally to the wind speed, but at constant voltage supply. A 10 Ω stable resistor is added serially to the thermistor for measuring the voltage drop and the current is calculated by dividing the measured voltage by 10 Ω. The maximum of thermistor current is limited to 100 mA with a current protection circuit. The momentary temperature on the thermistor is determined by measuring the thermistor resistivity. The momentary thermistor power is then determined by the parameters mentioned above. In that way calibration curves are derived serving for direct determination of wind speed for each resistivity value or thermistor current Ith measured.
Instead of a method of constant voltage supply a constant current supply method (constant self-heating) of segmented thermistors can be performed. In that case a thermistor voltage varies with cooling caused by airflow e.g., wind blowing on a certain axis. Calibration curves of wind speed are then a function of voltage Uth measured on the thermistor.
Calibration curves, for example thermistor current change vs. wind speed, in a certain quantity are dependent on the air temperature and humidity. Therefore two additional sensors were configured in the measuring anemometer system: temperature sensor (marked by T in Figure 1) and humidity sensor (marked by H in figure 1). The thermistor measuring the air temperature T (Figure 5) is not self-heated by a constant current and operates independently. It is in direct contact with air and its resistivity is a function of the air temperature. The humidity sensor H (figure 6) has two equal thick film segmented thermistors marked by (1) and (2) that- are placed in a Wheatstone bridge. Both of them are heated by self-currents through them after constant voltage supply: one is compensative and another is active. A current difference between compensative (2) and active (1) thermistors increases with an increase of humidity; in that way humidity vs. bridge output voltage is calibrated after air temperature is measured. Thermistors are placed in the differential branches of the Wheatstone bridge, linearized and balanced prior to use: humidity changes are measured as a function of the bridge output voltage. The humidity sensor is dependant on the air temperature in its operation. Using data of the air temperature from sensor T and humidity data from sensor H certain corresponding calibration curves for the wind speed on the x, y, z - axes are selected after the temperature and humidity are measured. The wind speed is determined by reading a value on a calibration curve.
The wind direction is determined by a temperature gradient on a segmented thermistor. Without a wind blowing, the supply voltage is nearly equally distributed over a segmented thermistor. When air is flowing through the sensors placed on x, y, z, -axes the equal distribution is changed. Half of the thermistor that is positioned closest to the airflow
400 cools more than the second half. Measuring the voltage distribution referring to the middle point of the thermistor in the wind direction is determined as follows: The airflow (wind) has a direction from the colder to warmer part of a thermistor e.g. from higher to lower resistivity or measuring the voltage from higher to lower voltage. This voltage difference is measured on inner electrodes of a segmented thermistor marked
405 by Ui and U2 in Figure 2: in fact it gives a positive or negative sign of direction of the airflow to the certain axis.
In the way described above, using calibration curves the wind speed and direction is determined on each axis x, y, or z and the total intensity is calculated as a vector modulus. The airflow direction - wind direction on a certain axis gives a sign
410 plus or minus to a wind speed towards a certain axis. The angles in relation to the x, y, z coordinate system, that the wind speed vector makes are determined from the vector self projections to the axes and vector modulus. The wind speed vector projections are measured previously as intensities of the wind speed vector decomposed to the axes.
415 Transition from the x, y, z- axes coordinate system to a spherical coordinate system is defined in trigonometry. Calibration curve selection, speed modulus calculation, determination of direction and angles, trigonometry formulae, polynomials for interpolation and measured responses recording of all sensors e.g. the total data processing for all sensors in the system is performed on a personal
420 computer (PC) using a multi-channel acquisition card (AQ) as an input card. Data from sensors is sent by wires or wirelessly to the PC in a local station. A block diagram of the sensors connection to an AQ-card and PC is given in Figure 7. Calibration curves are given in Figure 8 for room humidity and temperature of 20 0C. Time response of the uniaxial wind speed sensor is given in Figure 9 for fast changes
425 of wind speed from 0 to 2 m/s.
Possibility of rainfall is staled first by a humidity sensor as an overcritical humidity. Then a vertical wind speed is monitored by a wind speed sensor placed along the z-axis (sensor response to rainfall is measured). In the moment of rainfall fast cooling of segmented thermistor starts, that is equal to a fast and extremely high
430 change in the wind intensity down towards the z-axis. However for overcritical humidity and a fast temperature drop the z-sensor response is not explained by the PC as wind change in the z-direction, but as the start of a rainfall. At the end of a rainfall the z-sensor becomes warmer while overcritical humidity and lower temperature remain due to rainfall cooling. The wind speed sensors and humidity sensor can't be
435 ice covered in modest climatic continental conditions because of self-heating e.g. they are much warmer than the flowing air.
A full construction of a thick film segmented thermistor is given in Figures 3 and 4. Thick film segmented thermistor has an alumina substrate as a sensor. PdAg electrodes are placed in two rows e.g. alternately in a zigzag order. A NTC thermistor
440 thick film layer is placed as a middle layer (Figure 3) e.g. between two rows of electrodes. The thermistor paste was composed of thermistor powder (based on Mn, Ni, Co, Fe. -oxide mixture), an organic vehicle and glass frit. It was screen printed on alumina, dryed and sintered at 850 0C. A top view of a pair of segmented thermistors
445 is given in Figure 4. NTC pastes are commercially available.
An UI characteristic e.g. resistivity of a pair of segmented thermistors as a function of temperature is given in Figure 10. The total resistivity of a thermistor is a sum of resistivity of segments. The voltage supply is equally distributed over segments in the absence of wind or airflow. A segmented thermistor has a large
450 surface value opened for heat transfer. It can be used for temperature gradient measurements (inner electrodes) or determination of the airflow direction. It measures temperature integrally (outer electrodes) or partially e.g. differentially on segments. It can be trimmed abrasively by a long edge L- cut to tolerances as small as 0.1 Ω.
455 Industrial applicability
A three dimensional anemometer configured of thick film segmented thermistors is aimed for measuring and determination of wind energy on meteorological high post locations for long term monitoring of wind speed changes and its exploiting for wind mill generators. The anemometer presented above can
460 serve for direct remote control of wind energy and remote windmills adjusting to wind direction in real time.
Manufacturing of thick film segmented NTC thermistors is done by the inexpensive screen-printing technique. NTC pastes are composed in Du Pont, ESL, Heraeus etc., and for example CMS Materials Division in Belgrade. Characterization
465 and calibration of sensors are done in laboratories in airflow guides and climatic chambers with humidity prior to calibration in real conditions outside. 16-channel electronic acquisition cards are manufactured elsewhere, for example ED- Electronic Design, Belgrade or any other card similar to that. XP EXCEL and C++ for PC is a suitable tool for measuring sensor response, presenting channel (sensor) data in real 470 time, measuring time response, calculating wind speed modulus and angles, recording and presenting long term data and remote monitoring in real time.
The Applicant
475
1.
480

Claims

1. A three dimensional anemometer is configured of thick film segmented thermistors , aimed to measure the speed and direction of wind, temperature and humidity of air in modest climatic continental conditions, based on heat loss of thermistors heated by self-current after constant voltage supply, to collect, process and record data by PC, characterized by, three wind speed sensors placed in space along the x, y, z - axis, one additional sensor of temperature and one additional humidity sensor (Figure 1), realized by 6 equal thick film NTC segmented thermistors (its construction is given in Figure 4).
2. Sensor of temperature based on a thick film segmented thermistor measuring the air temperature by self-resistivity change characterized by a thick film segmented NTC thermistor (Figure 4 and 5).
3. Humidity sensor based on thick film segmented thermistors characterized by application of two thick-film segmented NTC thermistors (Figure 4 and 6) placed in parallel one to another.
4. Wind speed sensor operating as a dependant sensor measuring the intensity and direction of wind, using temperature and humidity data obtained from the temperature and humidity sensor as parameters for corrections, characterized by, integral measurements with all surfaces of thick film segmented NTC thermistors placed longitudinally along the wind direction (Figure 2), measures projections of the wind speed on an axis (x, y or z), giving the intensity and direction, using measured calibration curves, where the current is changed through a thick film segmented NTC thermistor as a function of wind speed, and using the inner electrodes of the same thick film segmented sensor for measuring the gradient of temperature to define the wind direction.
5. Rainfall sensor for sensing the beginning and ending of rainfalls after claim 1, characterized by, data of overcrm'cal humidity prior to condensation and the air temperature drop, changes in intensity and direction of wind speed on the z-axis e.g. fast change in resistivity in the z-sensor caused by rainfalls.
6. Segmented thick film thermistor realized by a hybrid screen printing technology, characterized by, number of segments connected in series, having input and output terminations and inner electrodes, placed in rows over and under a NTC thick film thermistor layer in the zigzag direction, using a number of electrodes to enable measuring of temperature via measuring resistivity, integrally or gradually at the same time, having a geometrical and thermal symmetry of construction and large surface value for absorbing or dissipating heat to the ambient air, having indirect heating or self-heating for measuring temperature or wind speed, with a two mode of operation; constant power supply and variable current for self-heating or constant self-heating current and variable voltage on the thermistor after wind blowing.
The Applicant
1.
PCT/YU2006/000015 2005-07-27 2006-07-19 Three dimensional anemometer comprising thick film segmented thermistors WO2007014400A2 (en)

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