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Ultrasonic Sensor for Smart Meters Aid Conservation

MTC ElectroCeramics introduced its piezoelectric ceramic components and ultrasonic sensors for flow measurement of utilities, including gas, heat and water. Ultrasonic flow measurement devices can be a key component of “smart meters” designed to display hour-by-hour real time information about energy usage and pricing, facilitating residential and commercial energy conservation efforts.

Smart meters are being promoted by a $3.4 billion Smart Grid Investment Grant under the American Recovery and Reinvestment Act. It will be matched by industry, for a total investment worth more than $8 billion. More than 40 million smart meters are expected to be deployed in American homes as part of this initiative.

MTC ElectroCeramics’ piezoceramic components for measuring flow, distance and level have excellent acoustic sensitivity and mechanical strengths to withstand high pressures. Their tightly controlled resonant frequencies are key to achieving consistently good sensitivity levels. MTC ElectroCeramics offers a range of electrode materials and geometries to help customers with efficient high volume manufacturing.

MTC ElectroCeramics also uses its piezoceramic materials to design and manufacture ultrasonic sensors for metering both gas and liquid flow measurement, taking into consideration customer-specific requirements for sensor housing that operates reliably under high pressure and a wide range of temperatures. The sensors are supplied in custom designed housings complete with acoustic matching layers that enhance sensitivity and also provide the required protection from the environment. MTC ElectroCeramics’ in-house sensor test facilities ensure the best possible design solutions for specific customer needs.

Ultrasonic flowmeters are a solid state technology with no moving parts, making them more reliable than conventional mechanical meters. They suffer no pressure loss, offer nearly maintenance-free operation and are more accurate than many competing systems. In addition, they are more adaptable to the type of useful electronic display of energy use envisioned by champions of smart meters.

MTC ElectroCeramics has been supplying piezoelectric ceramic components and ultrasonic sensors to major utilities conducting ultrasonic measurement of hot and cold water, heat and natural gas flows for nearly twenty years. The use of ultrasonics for metering has been widely adopted, with more than 3 million meters installed annually in the European market.

Sensors May Warn Troops of Vehicle Damage

Scientists at the U.S. Army Tank Automotive Research, Development and Engineering Center are researching armored vehicles made with built-in sensors that automatically report when they are damaged. The aim is to give troops real-time situational awareness of the health, condition and structural integrity of their vehicle’s armor.

Currently, the standard procedure is to go out of the vehicle, walk around and look at it.

Normal wear and tear can cause damage lamination and produce cracks that are invisible to the naked eye, and noise on the battlefield can prevent an armored vehicle’s occupants from hearing when small-arms fire causes damage.

Tiny sensors called piezoelectric transducers are manufactured right into armored plate materials and detect changes in the plates’ condition.

Basically the U.S. Army is using ultrasonic waves through the material as our probe on the health assessment of the armor. The sensors send automated reports to graphical displays in the crew compartment. TARDEC developers have devised a color-coded system: green indicates the armor is healthy, black points out damage such as cracks, and red shows spots where the armor has been hit, for example, by ground fire. The system runs a self-check each time the vehicle is turned on, and evaluations can be run manually at any time. Initial tests have been successful and show the sensors are energy-efficient.

Little voltage is generally needed to supply to the transducers to get them to send ultrasonic waves through the material and, in fact, they can even use piezoelectric transducer strips as a kind of energy harvesting device. Just driving the vehicle around could cause the sensors’ piezoelectric fibers to generate energy. When there’s any kind of strain or stress, those fibers will convert the mechanical deformation to a voltage, then that voltage can be stored in a battery, which can later be used.

Other future uses for the sensors go beyond signaling when armor is damaged. They also could be used to monitor temperature, act as antennas and perform other functions that would contribute to the survivability of U.S. servicemembers, including monitoring the condition of body armor.

The first phases of testing involved shooting armored plates made with the sensors inside TARDEC’s lab and analyzing the results. The next step is to test their durability in the field.

www.defense.gov

DNA Nanosensor Detects Disease

A portable instrument based on an ultrasensitive nanoscale sensor could detect bacteria in minutes, helping to catch infectious diseases early and prevent their spread. The simple, low-cost device should be available within three years, says Benjamin Miller, professor of dermatology and biomedical engineering at the University of Rochester Medical Center, and codeveloper of the sensor.

Right now, diagnosing common bacterial infections requires growing cultures in a laboratory over a period of days, but diagnosis could be greatly speeded by a number of new sensors based on various nanomaterials that are being developed for ultrasensitive, rapid DNA detection. The new instrument would take from 15 minutes to two hours for a diagnosis and could be used in doctor’s offices, hospitals, and homes.

Each sensor is a hairpin-shaped strand of DNA, complementary to the genetic sequence being targeted, that is fixed on a gold film. Gold quenches the glow of a fluorescent molecule attached to one end of the DNA. The DNA stays folded over until a target genetic sequence links to it. Its unfolding results in the fluorescent molecule moving away from the gold film and glowing, which can be seen under a fluorescent microscope.

Lighthouse Biosciences in West Henrietta, NY, is commercializing disposable cartridges to be used with the nanosensor technology. A blood or urine sample to be tested would be placed directly on the cartridge. The cartridge will be a lab-on-a-chip, with rapid, miniaturized ways to prepare the sample for testing. “In the cartridge there are steps for cleaning up samples, that is, extracting material you’re interested in and amplifying the [bacterial] DNA,” Miller says. The cartridge will then be placed in a small portable instrument that does the fluorescence imaging and analysis. Each cartridge should cost a few dollars, Miller says.

By attaching different DNA strands on the gold film, the same cartridge could screen for multiple pathogens, Miller says. So far, the researchers have made a sensor to detect antibiotic-resistant staph bacteria that cause skin infections. They are now working on detecting bacteria responsible for common urinary-tract infections. The sensors could also be used to quickly spot bacteria in food or bioterror agents in water supplies, or even to screen for genetic disorders or cancer.

In a newer version of the sensor, Miller and colleagues stick DNA strands on silver nanoparticles. The silver nanoparticles make the fluorescent signal 10 times brighter. Plus, because thin layers of silver nanoparticles are transparent, the sensor could be coated on glass and optical fibers to make new types of detecting instruments, Miller says.

Understanding Infrared Thermometry

John R. Gyorki
Editorial Director

Infrared (IR) thermometry appears to be rather straight forward: point, press the button, and read the temperature. However, measurement results will be quite disappointing without a thorough understanding of the instruments’ principle of operation and specifications.

Temperature measurement instruments can be divided into contact and noncontact types. Sensors used in contact-type instruments include thermocouples, resistance temperature detectors (RTDs), thermistors, and semiconductor temperature sensors. Since contact sensors measure their own temperature they require physical contact with the measured object to bring the sensor body to the object’s temperature.

In some applications this contact creates problems: The measured object or media may be located at a distance or in a hazardous environment with no easy access. Measurements of moving objects are also difficult. A small object’s temperature may be altered when a relatively large sensor touches it and acts as a heat sink.

Noncontact infrared (IR) thermometers, if used properly, offer convenient solutions for these and many other measurement applications. However, you should select the measuring instrument and measurement techniques to be compatible with the application.

How IR Thermometry works
Heat is transferred from one body to another through conduction, convection, or radiation. Radiation is a process where heat energy in a form of electromagnetic waves is emitted by a hot object and absorbed by a colder object. Most of this radiation is in the infrared (IR) region of the electromagnetic spectrum, but some also spreads into the visible light band. The IR wavelength band stretches from 0.7 to 1000 microns, however practical IR measurement systems use only certain wavelength bands between 0.7 and 14 microns because the radiation is the strongest in this range.

If an object is exposed to IR energy radiated by a heat source, such as an electric heater, light bulb, sun, or other source, the energy reaching the object is called incident energy.  Part of this energy is reflected off the object surface. Theoretically, the object’s coefficient of reflectivity can vary from 0 (no reflection) to 1.0 (100% reflection). Rough, matt surfaces have low reflectivity. Polished and glossy surfaces, especially metals, have high reflectivity.

Depending on the object material, thickness, and the radiation wavelength, part of the radiation can go through the object or be transmitted. The coefficient of transmission can vary from 0 (no energy transmitted through object) to 1.0 (100% energy transmitted through object). High transmittance examples include glass, quartz, plastic film, and various gasses. Materials opaque in the IR spectrum have close to zero transmission coefficients.

The remaining energy is absorbed by the object and raises its temperature. A hypothetical body that has no reflection or transmission and absorbs all incident energy across the entire spectrum has a coefficient of absorption equal to 1.0 and is called a blackbody. Real-life objects, referred to as gray bodies, have coefficients of absorption that fall between 0 and 1.0.

Incident energy, W_I, is defined as:

W_I = W_R + W_T + W_A

Where:
W_I =  incident energy received by the object, W
W_R = energy reflected off the object’s surface, W
W_T = energy transmitted by the object, W
W_A = energy absorbed by the object, W

As the object absorbs energy and heats, it also emits energy.  When an object is in a state of thermal equilibrium, the amount of energy it absorbs (W_A) equals the amount of energy it emits (W_E): W_A = W_E. When an object absorbs more energy and its temperature increases, the amount of radiation it emits also increases.

IR thermometry is based on the fact that any body (solid, liquid, or gaseous) that has a temperature above absolute zero (0^oK or -273^oC) emits radiant energy. This energy is proportional to the forth power of the body temperature, and the body’s ability to absorb and emit IR energy is called emissivity. Energy radiated by a body can be expressed as follows:

W = E σ T4 A

Where:

W = energy, W
E = emissivity
σ = Stefan-Boltzmann Constant = 5.6703 10^-8, W/m²K⁴
T = absolute temperature, ^oK
A = emitting area, m²

Emissivity can range from 0 to 1 for various bodies. A hypothetical blackbody emits and absorbs all energy and thus has an emissivity equal to 1. Real-life objects have an emissivity between 0 and 1.

When an IR thermometer measures an object’s temperature, consider the energy that actually enters the lens. That is, in addition to emitting energy related to its own temperature, the object may reflect energy coming from another source, or transmit energy passing through it from a source behind it. For accurate measurements, survey the surrounding area for possible sources of extraneous IR radiation and choose the thermometer position and aiming angle to minimize the effects of those sources.

IR Thermometers
Infrared temperature measurement instrument design varies from simple hand-held thermometers that can be purchased for less than a hundred dollars to complex special-purpose instruments that cost hundreds and even thousands of dollars. However, some building blocks are common for most designs.

A typical infrared thermometer consists of optical components, IR detector, electronics, and a display or interface output stage. Optical parts focus radiation energy onto the IR detector and filter out radiation outside the desired wavelength band.  These components include collecting optics, lenses, fiber optics, and spectral optical filters.

IR Detectors
The majority of IR detectors are either single-wavelength (also called single-color), or dual-wavelength (also called two-color) type. The single-wavelength detectors measure IR energy within a certain wavelength band, and the instrument calculates object temperature based on the detector output and the preset emissivity. Some thermometers have adjustable emissivity, and most simple units have fixed emissivity.

Dual-wavelength detectors measure energy at two different wavelength bands, and the instrument calculates temperature based on the ratio of the two readings. If emissivity or the energy changes by the same amount at both bands, the measurement accuracy is not affected. Emissivity or the amount of radiated energy may change due to object change or movement, lens contamination or misalignment, or view obstruction.  The dual-wavelength detector’s drawback is higher cost and lower accuracy under certain conditions.

Emissivity of many materials and surfaces remains relatively constant over the IR wavelength range, and measuring energy in any narrower band will be acceptable. Other materials have wavelength bands with higher and lower emissivity due to high reflectivity or transmission, and require narrow band detectors tuned to high emissivity wavelengths.

Another factor is the atmosphere. Its transmission coefficient vs. wavelength curve has many peaks and valleys, which swing from almost 1.0 to near zero and block the IR energy transmission. Most general-purpose IR thermometers use the largest high-transmission band between 7 and 14 microns to minimize atmospheric attenuation.

To measure temperature of objects with emissivity that varies greatly over the IR wavelength spectrum and objects obscured by glass, smoke, steam, or other barriers, engineers need to use narrow band IR detectors. For example, short-wavelength detectors handle variable emissivity objects, lens contamination, and measurements through glass windows. Long-wavelength detectors are more prone to errors due to emissivity changes, but have a wide temperature range.

Special applications, such as measuring the temperature of glass, crystal, flame, gas, and thin film require detectors with specific narrow bands.  For example, detectors with a narrow band centered on 5 microns give the best results when measuring glass temperature.  Metals and metallic foils usually require 1 micron detectors where they have the highest level of radiation.

Based on the principle of operation, IR detectors fall into one of two categories: thermal detectors and photo detectors (photodiodes). Thermal IR detectors absorb the incident energy, raise the sensing element temperature, and change the detector’s electrical properties: thermopiles generate thermoelectric voltage, bolometers change resistance, and pyroelectric devices change their polarization. In general, they are slower than photo detectors.

A thermopile is made by connecting several thermocouples in series and placing their hot junctions in contact with a black body that absorbs the incident IR energy and heats the hot junctions. The cold junctions are placed in the area of the detector with adequate heat sinking. These detectors have fast response, broad band, large dynamic range, and are frequently used in general-purpose, automotive, air conditioning, and human-body thermometers.

Bolometers use a slab of material that changes its resistance in response to a change of temperature. The circuit converts resistance change to a voltage change, which is further processed by the instrument. Bolometers are frequently used for measuring low-level IR energy, often as an attachment to a telescope.

Pyroelectric devices become electrically charged when their body temperature changes. To produce a usable signal, the incident IR energy has to “pulse”. The output peak-to-peak AC signal is proportional to the pulse energy. Since energy emitted by measured objects is usually steady, thermometers that use pyroelectric detectors have a mechanical or optical chopper in front of the sensor. These sensors are used in many home security systems.

Photo detectors are built on a silicon substrate with an IR sensitive area that releases free electrons when impacted by the photons. The flow of electrons produces electrical signals proportional to the incident energy. These detectors are often used as arrays in thermal imaging systems.

A detector needs protection from the environment, and the selected window material must allow the correct wavelength band to pass through with minimum attenuation. A zinc sulfide or germanium window is best for the long-wavelength detectors, glass is suitable for short-wavelength detectors, and quartz for the mid-wavelength spectrum. Some instruments use a fiber-optic light guide to direct the radiation to the detector.

Since all types of IR detectors produce signals in the microvolt range, a high-gain amplifier should follow the detector.  Detector output vs. temperature curves are not linear and fluctuate greatly with a change in ambient temperature. To remedy this a signal-conditioning circuit stabilizes the temperature and linearizes the signal. Many applications require an analog-to-digital converter (ADC) to convert the temperature reading to a digital format.

Hand-held and many other instrument types have a built-in display, while other devices connect to a computer, data acquisition system, or temperature control system via an RS232 or RS-485 cable.  Some instruments simulate a thermocouple output, others have a 0 – 20 mA or 4 – 20 mA current loop, or voltage output.

The key specifications and considerations for any IR thermometer application are field of view (FOV) and distance; spectral band; response time; accuracy and repeatability; emissivity of the object or media being measured; media between the object and IR thermometer, such as vacuum, air, steam, gas, glass, or other; object temperature range; mounted or hand-held application; and type of output signal or display.

The FOV characterizes the diameter of a circle (target) that the IR detector will “see” at a certain distance from the measured surface. However, there is always a minimum target diameter that depends on the optical system and detector size. The detector measures and averages temperatures of all objects within the target area.  FOV is commonly called distance-to-spot size ratio and is a ratio of the distance between the meter and the target to the diameter of the target.

For example, a 10:1 distance-to-spot size ratio means that if a measured surface is located 10 inches from the thermometer it will measure and average the temperature of a circle with 1 in.diameter. Move the thermometer away to 20 in. and the target will increase to 2 in., and so on. A thermometer with a 1:1 ratio will measure within a one-foot diameter circle when held one foot away from the target.

Thermometers designed for measurements of small areas have a very narrow FOV and measure temperatures of objects less than a tenth of an inch. For example, such a thermometer held near a component on a pc board will measure the temperature of just that component and ignore the
components around it.

Other optical systems allow accurate temperature measurement of a spot several inches in diameter at a distance of tens of feet. However, such measurements require accurate pointing. Though notches on top of the instrument provide some help, aiming lights and built-in laser pointers prove to be most helpful.

Unfortunately, a laser pointer may occasionally lead to erroneous measurements if the user is not familiar with the IR thermometer operation and the FOV concept. Some first-time users mistakenly think that the laser beam that they see has something to do with the process of measuring temperature.  They presume that the instrument displays the temperature of the tiny spot where the laser beam meets the surface. Such measurements will not yield satisfactory results.

Practical considerations

Here are some helpful tips:
• Avoid degrading measurement accuracy by environmental elements, such as dirt, dust, smoke, steam, other vapors, extremely high or low ambient temperatures, and electromagnetic interference from other devices.
• Select an IR thermometer with a wavelength band compatible with the measured object (especially high reflectivity objects) and with the media between the thermometer and measured object (especially glass, smoke, or steam).
• Select an instrument with a temperature range not much greater than the maximum application temperature. Wider than needed temperature ranges lead to lower accuracy or higher instrument cost.
• An IR thermometer averages the temperature of all objects within its field of view: Select the instrument with an appropriate FOV, and calculate the proper distance so that only the desired area is measured.
• Avoid hot objects near the measured object. They radiate energy that can be reflected or transmitted by the measured object into the thermometer FOV.

For more information go to:

www.omega.com

www.watlow.com

www.gesensing.com

www.raytek.com

www.murata.com

Ultrasonic Distance Measurement Sensor

Minneapolis, MN – SICK launches the UM30-2 Ultrasonic Distance Measurement Sensors, featuring a new EasyTouch display and keypad that enables easier setup, configuration, and access to advanced problem solving features. The UM30-2 line offers increased measurement performance and is 25% shorter, providing more installation options. These sensors are ideal for detection and distance measurement applications, such as roll diameter control, level control, clear bottle detection, and collision avoidance.

The sensors’ increased performance includes actual measurement enhancements and valuable advanced features that can be activated to solve common application problems. The sensors’ resolution has been improved and now offers 0.18 mm resolution throughout the entire measurement range of the UM30-2 family. The new EasyTouch display and keypad allow for easy setup and quick commissioning and provide access to 14 advanced features without using any external PC or programming module.

Advanced features enable users to connect multiple sensors together to act as one large sensor, which increases the sensing area for more robust collision avoidance or for monitoring difficult target surfaces. They can also be connected together and programmed to multiplex to avoid cross talk and mutual interference. Another common problem solved by using the sensors’ advanced features is to ignore foreground or background targets, making it ideal for level detection to ignore signal reflections from the rim of the vial/bin/hopper/bottle/tube and only output the distance to the material inside. These solutions were previously not available in standard ultrasonic sensors and now provide more opportunities for you and your customer.

SICK
www.sickusa.com

Sensors for Clean-in-place Applications

U-GAGE® M25U Ultrasonic Sensors specifically suit sanitary environments. The sensors, rated IP69K, IP67 (NEMA 6), are constructed of heavy-duty 316 stainless steel to withstand high-pressure washdowns, severe temperatures, and aggressive cleaning chemicals common in food and beverage applications.

The smooth barrel housing enables thorough cleanup with minimal effort. The units also include IP68-rated washdown cordsets and FDA compliant brackets. M25U sensors can be wired for either normal or high speed. Normal speed offers a longer sensing range, while high speed provides a shorter response time, ideal for high-speed counting applications.

Banner Engineering Corp.
www.bannerengineering.com

Measuring Stack Level of Parts

To track the quantity of parts available on a rack to ensure a push-through manufacturing process, one option is to mount two detection sensors either alongside or above the rack which can detect parts at two different levels, or for smaller parts you can check stocking level with a distance measuring sensor.

Leuze electronic
www.leuzeusa.com

Banner U-GAGE® M25U Ultrasonic Sensors

Minneapolis, MN—Banner Engineering Corp. introduces U-GAGE® M25U Ultrasonic Sensors, opposed mode ultrasonic sensor pairs specifically designed for use in sanitary environments. The sensors, rated IP69K, IP67 (NEMA 6), are constructed of heavy-duty 316 stainless steel, allowing them to withstand the recurring high-pressure washdowns, severe temperatures, and aggressive cleaning chemicals common in food and beverage applications. 

With a smooth barrel housing—free of threads, gaps or seams that could accumulate debris—M25U sensors allow for thorough cleanup with minimal effort. Additionally, IP68-rated washdown cordsets and FDA compliant brackets are available to further ensure reliable, long-lasting performance in the harshest environments.

M25U sensors can be wired for either normal or high speed. Normal speed offers a longer sensing range, while high speed provides a shorter response time, ideal for high-speed counting applications.

www.bannerengineering.com

Sensor Film Measures Very Low Contact Pressures

You’ve wanted a more sensitive pressure sensor.  Now, one has arrived.  Pressurex Zero® is a new sensor film that characterizes tactile contact surface pressure down to an extremely low 7.2 PSI (0.5 kg/cm2).  The flexible film can be placed between contacting or mating surfaces to instantly and accurately measure and map pressure magnitude and distribution.  Variations in contact surface pressure are immediately visible by the impression made on the film. The spatial resolution of the film is fine enough to expose minute surface defects and other imperfections.  The range for Pressurex Zero® is 7.2 – 28 PSI (0.5 – 1.97 kg/cm2). Read more

Ceramics Power Ultrasonic Toothbrush

Dr. Pierre Mourad, a research associate professor in the University of Washington Department of Neurological Surgery, was discouraged by the cleaning ability of his ordinary power toothbrush. He wondered if ultrasound, something he manipulates every day in his laboratory, could transform ordinary bubbles into pulsating bubbles that could help remove plaque bacteria and produce a deep, long-lasting feeling of clean.

To transform this idea into a commercially viable consumer product, Mourad joined forces in 2003 with Jack Gallagher, the former president of Optiva Corporation (developers of Sonicare®).  Read more

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