Randy_Shirts_Microwave Distance Sensor

8/7/2019 Randy_Shirts_Microwave Distance Sensor

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Microwave Distance Sensor

Randy ShirtsECE 5320

Mechatronics Assignment #1


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Ou

tline Reference list

Major Applications

Basic principle Typical configuration

Specifications

Limitations Choosing a sensor

Cost & Availability


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Reference List www.radatec.com/radatec/products2.html

www.sensorsmag.com/articles/1299/50_1299/main.shtml


data.engin.umich.edu/faculty_staff/faculty/Ruf/index.html

ccrs.nrcan.gc.ca/resource/tutor/fundam/chapter3/01_e.php

www.crisp.nus.edu.sg/~research/tutorial/mw.htm

nsidc.org/data/docs/daac/nsidc0165_clpx_gbmr/


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Fu

rther References http://ccrs.nrcan.gc.ca/resource/tutor/funda

m/chapter3/01_e.php

http://www.crisp.nus.edu.sg/~research/tutorial/mw.htm

http://www.radatec.com



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Major ApplicationsActive Sensors

When the distance betweensensor and the measuringsurface are large. Such as trainspeed control and heavyequipment testing

Vehicle speed and position

In very harsh conditions. Such

as a distance measurement in anengine

Passive Sensors Meteorology

Hydrology Oceanography


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Basic Working Principle Active Sensors (Close Range)

Active Sensors (Long Range)

Passive Sensors


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Active Sensors

(Large Distances) Noncontact microwave

sensors, or radar, sensorsare based on the Dopplereffect. Using the

frequency shift of a wavereflected from a movingsurface, microwavesensors are able tocalculate speed and

distance.


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Active Sensors(Small Distances)

The schematic below shows how the technology works.

First, a radio wave is emitted from the microwave sensor and impinges on thevibrating object. The signal is reflected and sensed in the radio receiver embedded in the sensor. This signal is then acted on by specialized electronics and an algorithm that

converts the electrical signal to a calibrated measure of displacement. The measured distances resulting from these techniques are on the order of

microns, not miles.


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Passive Sensors All objects emit microwave energy of some

magnitude, but the amounts are generallyvery small. A passive microwave sensordetects the naturally emitted microwaveenergy within its field of view. This emittedenergy is related to the temperature andmoisture properties of the emitting object orsurface. Passive microwave sensors aretypically radiometers or scanners and operatein much the same manner as active

microwave sensors except that an antenna isused to detect and record the microwaveenergy.

The microwave energy recorded by a passivesensor can be emitted by the atmosphere (1),reflected from the surface (2), emitted fromthe surface (3), or transmitted from thesubsurface (4). Because the wavelengths areso long, the energy available is quite smallcompared to optical wavelengths. Thus, thefields of view must be large to detect enoughenergy to record a signal. Most passivemicrowave sensors are thereforecharacterized by low spatial resolution.


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Aircraft Turbine Health

Monitoring Waveforms of blade profile, comprised of distance measurements across blade tip as it

passes the sensor at 18,000 rpm.

The R2000 Displacement Sensor measures displacement by launching a continuous-wave microwave signal towards a target of interest and comparing the received signal

with the transmitted signal. The sensor extracts information on the target movement from the return signal.


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The first figure represents profiles of bladetaken over time. The variability in bladelength for this blade is representative ofnormal blades.

The second figure represents a blade with anabnormal amount of length variability due topreviously undetectable fatigue in the bladeroot.

This system is used to predict failures inturbine blades, disks, and rotors for jetaircraft turbines. The environment involvesblades rotating at 18,000 rpm within flamingnatural gas, carbon, oil and othercontaminants. The system employed iscomprised of the 2000F high tempcylindrical probe, nickel alloy cable, and highspeed data acquisition electronics. For thisapplication, the system takes data at 25 MHzand provides a data point every 0.0007across each blade on each revolution. Thesedata-rich waveforms enable maintenancepersonnel to predict blade creep fatigue,blade cracking, disk cracking, and othercatastrophic failures


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Microwave Motion Sensors for

Off-Road Vehicle Velocity Data and Collision Avoidance

Ground Speed Measurement Theconventional way to determine ground speedis to measure a wheel's rotational velocity andcompute the speed based on thecircumference of the tire. There are twoproblems with this method. First, calibration

depends on the type and age of the tire;second, wheel slippage depends on soilconditions and the load on the vehicle. Wheelslippage can average 20%--25% in the field,although 11%--14% is optimum for the stresson the vehicle and soil compaction [2]. Tohelp tractor operators optimize vehicleperformance, John Deere has developed aunit that incorporates a microwave sensorwith a wheel tachometer to calculate wheelslippage. This unit also provides true groundspeed. According to an extensive study byCalifornia Polytechnic State University atSan Luis Obispo, there is no correlationbetween wheel slippage and true groundspeed [3].


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Environmental Specifications. Any sensor designed to be used in theagricultural environment must meet stringent specifications forresistance to vibration, salt spray, high humidity, fertilizers,pesticides, and so on. A group of specifications has beendeveloped to address this requirement , among them:

Operating voltage: 10 VDC16 VDC Power consumption:


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TOPEX Altimeter Sensor/Instrument

TOPEX/Poseidon (T/P) is a jointNASA/CNES mission which imagesglobal distributions of sea level withunprecedented accuracy andprecision. The primary instruments areradar altimeters designed to determinethe radial distance between the satellite

and the ocean su

rface by a precisemeasurement of the round trip time offlight of the radar signal. This distancecan be translated into a measurement ofthe sea level along the T/P ground trackgiven accurate knowledge of thelocation of the satellite in earthorbit. Critical to the success of themission are corrections for the variable

propagation delay caused by theintervening atmosphere. The correctionfor columnar water vapor are measuredby the TOPEX Microwave Radiometer


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Major SpecificationsClose Active

Range(0.01 to 2.0) Resolution 0.0004 inches Linearity 0.75% (Deviation-from-straight-line) Power +12 VDC (2A) Operating Temperature

Probes: Up to 2000 FRF Module: 0 to 185 FTeflon Coaxial Cable: 350 FMineral Insulated Coaxial Cable: 1500 F

Humidity0 to 100% non-condensing

Contaminant ImmunityImmune to dust, dirt, oil, and other industrial debris

EMIImmune to EMI


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Typical Long Range Active Min-Max Speed: 3 to 309 mph

Accuracy: 1% PowerOutput: 5 mW Power Required: 10 to 26 VDC,

3 W Size/Weight: 4 4 8 inches/2

lbs.

Typical Passive Sensors Frequencies: 1 to 100 GHz

Measurement Range: 0 Km to350 Km

Absolute Accuracy: 0.5 K, 0.4K (RMS) over 10 minutes/ea

Resolution: 0.3 Km min

Antenna Beam Width: 10 deg.(FWHM) Beam Efficiency: 98% min Cross Polarization: 0.1% max Sidelobe level: -40 dBi max Polarization: V & H (23.8 GHz

only V) IF Bandwidth: 200 MHz


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Active Sensor LimitationsClose Range Offered by only one

company Work only with vibrating

objects

Long Range Possible health problems

related to electromagneticradiation (not proven yet)

Wet surfaces causeproblems because of thedielectric constant

The geometric shape ofthe reflective surface maycause error (can be limitedby signal processing)


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Passive Sensor Limitations Physical factors such as the dielectric constant of

the surface materials which also depends stronglyon the moisture content

Geometric factors such as surface roughness,slopes, orientation of the objects relative to theradar beam direction

The types of landcover (soil, vegetation or man-

made objects) Microwave frequency, polarisation and incidentangle all aaffect the output


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Choosing a SensorActive Close Range

Contact Radatec

Determine the rangeneeded

Optional features Opto-isolated digital inputs

Relay outputs

Data memory

Clock

Active Long Range

Determine the range

Operating frequency Temperature requirements

Power consumption

Signal processing

elements


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Where to Bu

y Active Close Range Radatec

www.radatec.com

Active Long Range Search www.globalspec.com for proximity or

velocity microwave sensors

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