Termperature sensors are used today in many industrial and everyday environments for control and monitoring purposes. To make the most of your existing temperature sensors or to learn more about this sensing technology, Sensor Tips has provided the latest news and information for your reading pleasure.
Sensors Expo 2010 Exhibitors: Tellurex Corporation and Dexter Research
June 18, 2010 by Randy Frank
Filed under Energy Harvesting, Featured, Temperature
If you missed Sensors Expo or did not get a chance to check out all the exhibits, here is another of the interesting booths that I visited. Chuck Cauchy from Tellurex and Wayne Baer from Dexter Research explain each company’s role in developing an energy harvesting powered wireless sensor. To see the video, click the arrow link below.
For more information about Tellurex for thermoelectric solutions, click here.
For more information about Dexter Research for wireless sensing solutions, click here.
Ease Temperature Concerns: We’ll Call You
May 13, 2010 by Randy Frank
Filed under Featured, Temperature, Wireless
Adding to its USB, and Wi-Fi editions, Temperature@lert Cellular Edition monitors the ambient temperature in a server room or other critical area and alerts the user via email, telephone and text message when the temperature rises or falls outside of an acceptable range. The pre-calibrated digital temperature sensor is accurate to within ±0.5°C with a range of -40°F to +200°F. Plugging the Temperature@lert Cellular Edition into a power outlet initiates transmission of temperature readings over the AT&T and T-Mobile cellular phone networks to the company’s 24/7 monitoring system and dashboard website.
For more information on Temperature@lert Cellular Edition go to: http://www.temperaturealert.com/Remote-Temperature/Temperature-Alert-Cellular-Sensor.aspx
World’s Smallest Digital Temperature Sensor Ideal For Harsh Environments
May 11, 2010 by admin
Filed under Temperature
With the new SHT21, Sensirion launched the world’s smallest digital humidity and temperature sensor. The SHT21 consists of a newly designed, sophisticated sensor chip encapsulated in a 3×3x1.1-mm DFN 3-0 package. Over-molding provides excellent protection against aging and ambient impact, such as condensation and harsh environments, and thus yields outstanding long-term stability.
The SHT21 is fully calibrated and provides an I2C digital interface. Analog output modes (such as PWM) are available on request. The digital communication mode enables superb low power consumption: A value in the range of 3μW at normal operation is well achieved. Typical sensor accuracy is ±2% RH over 20–80% RH and ±0.3 °C over 25–42 °C. Provided on tape & reel, the reflow solderable SHT21 is suitable for high volume applications. Furthermore, the sensor is qualified in accordance with automotive standard AEC-Q100 and an extended quality assurance program guarantees low PPM values.
Wireless Sensor Checks Temperature Of Your BBQ Meats
May 6, 2010 by admin
Filed under Featured, Temperature
The NI Wireless Sensor Network (WSN) platform gave BMF Cooks another tool in the BBQ pit when they went to competition at the 2010 Austin Rodeo. By monitoring the temperature of the various meats as they cooked in addition to providing temperature gradient information inside the pits, NI WSN measurement nodes enabled the cooks to supply rodeogoers with delicious, perfectly-cooked BBQ that was worthy of second place in the 29th annual Austin Rodeo BBQ competition.
BMF Cooks is a collection of NI Employees that have turned their love of BBQ into a non-profit organization benefiting an Austin-based youth scholarship fund. This is their 5th year competing at the Austin rodeo, and their highest finish so far in the competition.
The LabVIEW-powered application used a combination of WSN-3212 thermocouple measurement nodes and WSN-3291 outdoor enclosures to monitor eight temperature channels on each of the two BBQ pits. A conveniently-placed computer monitor allowed hungry patrons to view cooking temperatures and pit temperatures while they were served their dishes. The newly-released NI 9792 Programmable WSN Gateway used an integrated web server to publish the temperature data to the web, so that patrons could monitor the status of the meats on their smart phones while roaming the fairgrounds, alerting them when the freshest round of BBQ was ready to be served.
Environmental Sensor Has Wide Variety Of Indoor Applications
April 30, 2010 by admin
Filed under Temperature
Carlo Gavazzi Automation, the international electronics Group with activities in designing, manufacturing and marketing of electronic equipment, launches the CGES Series, a new range of sensors designed to measure various indoor environmental parameters, including CO2, Humidity, Temperature and Air Velocity.
When CO2 levels rise to an unacceptable level, with poor air quality and stuffy rooms, the CGES sensors can be used to help increase the supply of fresh air into the building and, as a result, improve the indoor air quality. The CGES sensors can be a significant contributor to compliance with ASHRAE 62-1989, which recommends a maximum concentration of 1,000 ppm of CO2 indoors. Additionally, the auto-calibrating feature ensures that the CGES is properly tuned for continuous, worry-free operation.
The CGES Series can also be used to control humidity levels in wet climates, thus elevating the comfort level of the occupants and discouraging the growth of mildew. Air velocity and temperature sensors can be used to keep indoor air temperatures at comfortable levels, and maximize energy efficiency.
All of these new sensors operate on 24 VAC/DC for flexibility, and feature multiple output options, including 0-10V, 4-20mA, and switching. They can be mounted in walls or ducts. The CGES sensors are a complete and versatile solution with applications in office buildings, schools, pools, museums, green houses, incubators, and food storage rooms, among many others.
Sensor Measures Dissolved Nitrate In Water
March 2, 2010 by admin
Filed under Level, Liquid Level, Temperature
Featuring a precision nitrate ISE electrode sensor with an integral self-cleaning sprayer, the new HYDRA Nitrate Analyzer System from Electro-Chemical Devices, Inc. (ECD), offers superior measurement, monitoring and control with virtually no maintenance.
The highly intelligent HYDRA Nitrate Analyzer System measures the concentration of dissolved nitrate as nitrogen (NO3–N) in water. The sensor uses two electrodes to determine the NO3–N concentration: a nitrate ion electrode and a chloride ion electrode. An optional electrode is also available for pH measurement.
The system’s HYDRA Analyzer is configured to periodically actuate a cleaning cycle using the integral spray cleaner in the nitrate sensor, minimizing the formation of biofilms or other coatings on the electrodes and keeping maintenance to a minimum. The cleaning cycles feature a user configurable period and duration. During the cleaning cycle the 4-20 mA output is held at either a preset value or the last value.
While useful in all types of water treatment applications, the HYDRA Nitrate Analyzer System is especially well suited for municipal wastewater treatment plants. Nitrogen primarily enters a municipal wastewater system as ammonia/ammonium compounds. Nitrification oxidizes the toxic ammonium ion into a much less toxic nitrate ion using an aerobic activated sludge process.
De-nitrification reduces the nitrate ion (NO3-) to nitrogen gas (N2) through an anoxic reaction in the same treatment basin or in a separate anaerobic digester. The NO3–N measurement helps optimize the methanol being fed to the digester, which minimizes cost and provides trend measurement of the total nitrogen (TN) in the effluent.
The nitrate ion electrode provides the primary measurement. A second electrode measures the Chloride ions in the sample. The HYDRA Analyzer subtracts the appropriate amount of signal from the nitrate measurement for accurate monitoring. The sensor also detects temperature, and the analyzer provides a temperature-compensation calculation for superior measurement accuracy.
The rugged nitrate sensor offers 1.25-inch NPT rear facing threads for attaching an extension/immersion tube for easy installation from catwalks or handrails. Internal signal conditioning allows the sensor to be mounted up to 200 meters from the analyzer. The sensor is extremely low-maintenance, featuring a movable electrode guard to facilitate easy electrode replacement when necessary.
ECD’s HYDRA Nitrate Analyzer System measures nitrate and chloride in concentrations from 0.1 to 1000 ppm, pH from 0 to 14 and temperature from 0 to 50°C (32 to 122°F). Accuracy is ±3 percent of reading with a response time of T90 1 minute.
Featuring a backlit LCD display that provides up to 4 lines of text and graphics, the HYDRA Analyzer includes two 4-20 mA outputs with two SPDT alarm relays. Input power is 110/220 Vac. It is housed in a rugged NEMA 4X enclosure.
New Sensors & Instruments Solutions Guide from Minco
February 16, 2010 by admin
Filed under Featured, Temperature
Minneapolis, MN — Minco has a new, free guide that walks you through defining your temperature sensing application requirements and choosing the best sensor and instrument solution. This guide will also help you determine what sensing technology is best, show you how to compare sensor alternatives and help you obtain parts for testing and prototyping sensors. The Sensors & Instruments Solutions Guide can be ordered in print from Minco’s website or downloaded free.
If you have any responsibility regarding temperature sensing, transmitting or recording, you must have this Catalog in your library. This new publication has a number of improvements including:
• It highlights the 255 parts that are in stock and ready for fast delivery. It also shows thousands of other standard sensor designs and explains how to work with Minco engineers to build a custom sensing solution.
• It includes several brand new products such as a compact plug sensor, integrated sensor/transmitter assembly, conductivity level sensor, programmable “smart” transmitters and more.
• It offers a full line of sensor and transmitter assemblies with calibration accuracy options to meet virtually any temperature sensing application requirement.
• Streamlined, simplified ordering and quick access to part drawings.
• Choose from many Explosion-proof and Intrinsically-safe sensor designs for your applications in hazardous areas.
The 172-page guide explains various temp sensing solutions for process control, building automation, defense, aerospace, machinery and industrial and commercial equipment. The guide has complete technical data on sensor assemblies, probes, miniature sensors, sanitary sensors, stator RTDs, HVAC temperature and humidity sensors, flexible sensors, elements, instruments, transmitters and accessories. In addition to the Guide, a Non-Invasive Sensors Design Kit is also available.
Minco
www.minco.com
Low Power Requirements – High Temperature Ratings
October 8, 2009 by admin
Filed under Featured, Temperature
The Low power requirements on the Microchip Technology Inc. sensor doesn’t keep the MCP9804 Temperature Sensor from providing a high temperature accuracy of +0.25° C (typical) and +/- 1° C from -40 to +125°C, as well as static current consumption of just 200 µA.
Many temperature-sensing designs require the use of several external components, making them large, complex and expensive. Silicon-based temperature sensors are becoming more popular because they do not require external components and can be used with little to no design experience. In addition to low power and high accuracy, the MCP9804 sensor features programmable shutdown to extend battery life; an alert feature for over- and under-temperature window monitoring; and a critical temperature-alert feature that provides over-temperature protection, helping to further lengthen system life.
“The MCP9804 temperature sensor represents a significant expansion of Microchip’s temperature-sensor family,” said Bryan J. Liddiard, vice president of marketing with Microchip’s Analog and Interface Products Division. “The sensor gives designers a tremendous amount of flexibility to design smaller, higher-performing temperature sensing systems at lower costs.”
Example applications for the MCP9804 temperature sensor include industrial freezers that require high accuracy at lower temperatures such as -20° C to +45° C; consumer electronic devices that require high accuracy at +85° C, such as personal computers; and automotive applications that demand high accuracy at temperatures up to +125° C, such as engine temperature monitoring.
Understanding Infrared Thermometry
September 14, 2009 by John R. Gyorki, Editorial Director
Filed under Temperature, Ultrasonic
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.
Omega Engineering’s model OS523E/524E Series infrared thermometers measure target temperatures without physical contact. Values are stored, displayed on the LCD, and outputted as RS-232 and analog signals. –Reproduced with permission of Omega Engineering, Inc., Stamford, CT 06907 USA www.omega.com.
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, WI, is defined as:
WI = WR + WT + WA
Where:
WI = incident energy received by the object, W
WR = energy reflected off the object’s surface, W
WT = energy transmitted by the object, W
WA = energy absorbed by the object, W
When incident heat energy reaches an object, part of this energy is reflected, part passes through the object, and the rest is absorbed. The coefficients of reflection, transmission, and absorption depend on the object material and surface finish and on the wavelength spectrum of the incident energy.
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 (WA) equals the amount of energy it emits (WE): WA = WE. 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 (0oK or -273oC) 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
When the temperature of a hypothetical blackbody increases, the radiated IR energy also increases. Temperature T2 is several times greater than temperature T1. The rise between 1 and 10 microns is most pronounced.
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.
A typical infrared thermometer consists of optical components, IR detector, electronics, and a display or interface output stage. Optics focuses IR energy onto the detector that converts the IR energy into an electrical signal. After amplification, linearization, and temperature stabilization, the electrical signal is converted to a value representing the measured temperature. Many instruments have a built-in display, others connect to measurement or control system, or to a computer.
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:
Digital temperature sensor line
August 24, 2009 by admin
Filed under Featured, Temperature
Franklin Lakes, NJ — Digital electronics and precision engineering contribute to the small size of the latest addition to Process Sensor Corp’s IR thermometer line.
Process Sensor DS-40N Temperature Sensor
The DS-40N and DG-40N series of stainless steel pyrometers are 124.5mm long overall by M40×1.5 threaded diameter, operate in a current loop powered mode to produce a linear 4 to 20mA output over selected temperature ranges from an overall span of 250 to 2500°C in two models.
In a 4 wire mode, the sensor also offers green LED, illuminating the exact target size, or laser aiming.
Depending on the model, either DS-40N or DG-40N, and temperature range, selected optics provide small target, close focus e.g. 1.2mm diameter at 210mm distance, or extended focus out to 4m with a 20mm diameter target.
A USB connection gives access to PC adjustments of such parameters as emissivity, response time, temperature sub-range and peak picker, with supplied software.
These non-contact sensor will operate in ambient temperatures up to 70°C without cooling. Adding the optional cooling and lens-purging jacket can extend ambient temperatures higher to 200°C .
The Model DS-40N has a spectral response of 0.8 to 1.1µm, and the DG-40N 1.5µm to 1.8µm, for minimum vulnerability to variable target emissivity, and to optimize the effective emissivity of low radiance targets.
The temperature ranges, optics, rugged construction and signal processing capability will appeal to users in the Steel, Ceramics and Glass Industries, Cement and Refractory manufacture, Induction Heating and Sintering operations.
Process Sensor “PSC Spot Software” supports sensor set-up, multi-tasking, graphic display of temperature trends, and data logging, and in general allows the user to customize the sensor to the application.
