Week 7 - Temperature Sensors

Temperature sensors are extremely important in modern life. Chemical engineering, modern medicine, and many other fields demand that the exact temperature be measured constantly. These sensors have to be extremely precise in order to maintain effectiveness. Specifically relating to BIM, temperature sensors are utilized to maintain a level of desired temperature for the inhabitants while also making the building energy and cost effectiveness. Temperature sensors have been a household item since the development of the mercury thermometer. These thermometers, or filled system thermometers, are filled with a liquid material with a high thermal expansion rate. This material then expands with the increase of molecule movement, or increase in heat. This sensor is ultimately reading and reacting to the increase or decrease in molecular movement, which controls how the liquid expands or contracts. (Middleton 1966)

The most commonly used temperature sensor today would be thermocouples. These types of sensors monitor temperature using electricity, like many modern sensors. This sensor is comprised of two different conductors in long, tube-like fashion. These conductors are placed a different temperatures, one location being the reference temperature, and the next being the location in which the temperature is trying to be measured. The differences in temperature between the reference point and point of interest produces a voltage which is then analyzed by a computing system to then provide the temperature at a certain point. These systems are inexpensive and require no external power, much like a filled system thermometer, which makes them highly popular. However, thermocouples are not extremely accurate and should not be used when extreme accuracy and precision is required. (Babadi 2011)

A pyrometer is another type of temperature sensor which utilizes a different approach from both thermometers and thermocouples. Radiation pyrometers measures the radiation of a given light, either visible or infrared, and then this this radiation heats an internal thermocouple to create a voltage. These types of sensors are used in non-contact situations.  (Stein 1994)

Temperature sensors are invaluable to BIM, as well as many other fields. Creating comfortable and cost-effective buildings require that the temperature be monitored and maintained at all times. These devices are not as simple as many people think however. And in order to utilizes them properly, one must understand what these sensors are actually doing.

References

Babadi, S. (2011, April). Sensors and their Applications. In 10 th Research Seminar Series Workshop.

Middleton, W. E. K. (1966). A history of the thermometer and its use in meteorology (p. v). Baltimore, Md.: Johns Hopkins Press.

Stein, A. (1994). U.S. Patent No. 5,308,161. Washington, DC: U.S. Patent and Trademark Office.

Comments

Melanie- Great post outlining the current state and limitations of motion sensors. I am curious how much these will actually advance. Do you believe that motion sensors could be improved enough to be utilized for other systems? I agree that the lighting system is one of the few systems in which motion detectors are effective and not annoying. Even then, motion sensors can become aggravating if the lights keep turning off.

Nameta- I really enjoyed that you brought attention to the fact the humidity is just as important as temperature in terms of indoor air quality. These types of sensors are very important to maintain a healthy indoor space as well as a comfortable one. BIM aims to create the most effective building and being able to monitor the humidity is extremely important.

Week 7: Motion Sensors

Commercial buildings consume a vast amount of energy, and one way to reduce that is through the use of motion sensors.  In the simplest of explanations: motion sensors help buildings reduce their energy consumption by altering systems of occupancy, signaling them to turn on or off.  Occupancy information can be used to control various systems within a building: lighting, HVAC, computers, etc.  Passive infrared (PIR or PID) is the most common type of motion sensor found in buildings today.  PIR sensors work by detecting changes in infrared radiation and maps it against a predefined gradient.  This type of sensor has a low resolution: it has the ability to detect a change, but not specifics about the occupant.  This keeps costs low for both the physical sensor and the installation/maintenance costs.

Due to the inability for motion sensors to reliably communicate with other sensors, limited accuracy, and a lack of data collection capabilities, motion sensors are typically only used to control the lighting system.  The electrical consumption due to lighting can be upwards of 60% of the building’s total electrical use.  Occupancy sensors need to be able to sense movement in the room, so accurate calibration and placement within the room are a key aspect of them functioning properly. 

I think the accuracy and interaction between motion sensors will increase very rapidly due to the fact that sensors are becoming more powerful and cheaper – allowing more to be used and the data gathered and studied for further improvements.  The ability for systems to turn on and off automatically will greatly reduce the energy consumption of buildings.

Sources:

Melfi, Ryan; Rosenblum, Ben; Nordamn, Bruce; and Christensen, Ken, “Measuring Building Occupancy Using Existing Network Infrastructure.” IEEE, 2011.

Garg, Vishal and Bansal, N.K., “Smart occupancy sensors to reduce energy consumption,” Energy and Buildings, vol. 32, 2000, pp. 81-97.

Leephakpreeda, Thananchai, “Adaptive Occupancy-based Lighting Control via Grey Prediction.”  Energy and Buildings, vol. 40, 2005, pp. 881-886.

Comments on Other Blogs:

Audrey Ryan: Your post was extremely enlightening.  I like that you went through the different types of temperature sensors.  I am interested to see which type of sensor is used in different applications.

Ryan Taylor: I found it interesting how you thought about movement sensors: I was very narrow in my scope limiting my view on motion sensors to lighting control in rooms.  This is a great way to showcase how many different ways one type of sensor can be used.


Dave Barbalace: Do these seniors have the ability to interact with the HVAC unit to control the moisture or are they more used for alerting someone of the moisture level?  I think it is amazing that it is so small!  

Group C Humidity Sensor Week 7

                                                             Humidity Sensor

Humidity is the amount of water vapor in car. It could affect human comfort and some industrial systems as well. So humidity sensor is needed in order to control systems for industrial process and human comfort. Humidity controls are important for semiconductor industry, medical applications and biological products. So humidity sensors are employed to provide an indication of moisture levels in the environment.

Common units for humidity measurement are relative humidity, Dew/Frost point and parts per million. Relative humidity indicates temperature; Dew/Frost indicates pressure of gas and parts per million is an absolute measurement. Dew point is used as an indicator of water vapor in high temperature processes.

Humidity sensors are divided into two types, the relative humidity sensors and absolute humidity sensors. But most of the humidity sensors are relative humidity sensors. Humidity sensors are consists of a hygroscopic dielectric material in the small capacitor. At normal room temperature, the dielectric constant of water vapor has a value of about 80, a value much larger than the constant of the sensor dielectric material. Therefore, absorption of water vapor by the sensor results in an increase in sensor capacitance.

Relative humidity is a function of both the ambient temperature and water vapor pressure. The relationship between relative humidity, the amount of moisture and the sensor capacitance can governs the operation of a capacitive humidity instrument.

Basic structure of capacitive type humidity sensor is shown below:

Lower electrode is formed using gold, a polymer layer such as PVA is deposited on the electrode and this layer senses humidity. On top of this polymer film, gold layer is deposited which acts as top electrode. The top electrode also allows water vapor to pass through it, into the sensing layer. The vapors enter or leave the hygroscopic sensing layer until the vapor content is in equilibrium with the ambient air or gas. Thus capacitive type sensor is basically a capacitor with humidity sensitive polymer film as the dielectric.

Basic structure of resistive type humidity sensor is shown below

Resistive type humidity sensors pick up changes in the resistance value of the sensor element in response to the change in the humidity. A polymeric film is applied on the electrode; the film acts as a humidity sensing film due to the existence of movable ions. Change in impedance occurs due to the change in the number of movable ions.

Reference:http://pasternack.ucdavis.edu/files/6213/7271/8210/hyd151_read13.pdf
http://www.engineersgarage.com/articles/humidity-sensor

To Qian: I found that the movement sensor is useful from your post. I learnt the difference between radar sensor and infrared sensor, but they are both movement sensor. They are used in automatic doors, automatic lights and building security. I agree with you that the sensor technology will continue to grow and contribute to modern age.

To Qi: I just figure out that the flow sensor can be used in the automobile industry. It’s interesting that the airflow can tell the computer to adjust how much fuel need to be added into the motor. And I agree with you that the accurate flow sensors ensure the safety of the process.

Week 7 - Movement Sensors, Group E

The general definition of the movement or motion sensor is a device that detects moving objects, mainly people, then perform a task, send a signal, or alarm a user of a motion on that area. There are different types of motion detections methods that used in motion sensors. Some of these popular methodes are:

·      Passive infrared (PIR): these detectors measure the change in the energy of the surrounding area. Their limitations are that they’re really sensitive to the environmental changes as hot or cold airflow, which might cause sending a false alarm to the user.

·      Active infrared (AIR): these detectors works by an IR emitter sends a beam of an IR, which will be received by an IR receiver; so, when the IR beam interrupted, the motion is detected. Typical uses of AIR are in automatic trash bin, water tabs, and automatic doors.  Their limitations are that they can be easily seen; therefore, using it in a security system is not good idea.

·      Ultrasonic: it has the same process as the AIR but instead of an IR beam, it’s an ultrasonic.

·      Optic-based: it’s basically a camera takes or records several frames and detects any different between these frames. When there is a difference, a motion is detected.

The most common types used are the AIR and PIR. The main difference between these two types are that the AIR is sending out signals and search for motion on the surrounding area while the PIR is reacting to a signal that reaches to the detector.

The motion sensors used outdoor and indoor in many of nowadays building. Motion sensors often used in indoor space to control lights, while they are used often in outdoor spaces as an alarm system. When using motion sensors in outdoor area, it’s important to select the one are rated for outdoor usage since the indoor models do not have the enough protection to prevent the electronics on the circuit board get damaged by the moisture or heat effects.

Using motion sensors is a great way to save energy and costs. As an example, by using motion sensors in controlling lights will turn off the lights when there is no motions so both energy and electric cost would be reduced.  

Sources

"Using Motion Sensors Outdoor." Smarthome. N.p., n.d. Web. 18 Feb. 2014. <http://www.smarthome.com/sh-solutions-use-motion-sensors-outdoors.html>.

"Different Types of Motion Sensors." Different Types of Motion Sensors. Sand Hill Engineering Inc, Jan. 2007. Web. 18 Feb. 2014. <http://www.shed.com/tutor/sensors2.html>.

http://media.digikey.com/pdf/Data%20Sheets/Panasonic%20Electric%20Works%20PDFs/AMN%20Design%20Manual.pdf

Week 7, Movement Sensor, Group E

This week, our group’s is to explore Movement sensors, here is what I learned from several articles I read. Movement sensor is also known as Motion sensor, it is everywhere around our life today. These sensors were invented during World War II because army needs it to detect of enemy air-crafts, and now it has been developed to apply to our everyday life. Movement sensors are in used in areas such as grocery store doors and security systems. I will give a brief introduction about two type of movement sensors that has been widespread used: radar sensor and infrared sensor.

Radar Sensors:

Radar sensors work by "radiating electromagnetic energy and detecting the echo returned from reflecting objects" [1]. The electromagnetic energy, which is in wave-form, is sent into the environment by a transmitter. When the wave reach to an object, it will reflect and be sent back in the opposite direction, scientists call this an echo. A receiver is used to collect the data from the echo and analysis to see if there is anything changed in the environment. Radar sensors are also called active sensors because they radiate energy in order to detect changes in the environment.

Infrared Sensor:

Unlike radar sensors, infrared sensors are passive; this means that instead of radiating energy in order to detect changes in the environment, they are capable of detecting radiation emitted by other objects, such as thermal energy from human beings [2]. Infrared sensors are made from different materials that sense different ranges of infrared wavelengths. When an appropriate wavelength of infrared radiation strikes one of the material's cells, it changes the cell's resistance. By measuring the resistance of the cell, one can measure its infrared radiation [3]. Since many different objects will emit a certain level of infrared radiation, it is easy for the sensors to detect rapid changes in infrared radiation instead of a particular wavelength. When the sensor detects a change, a device will be triggered to work.

Both Radar sensor and Infrared sensor are movement sensors. Sensor technology has already implemented in a lot of buildings, such as automatic doors, automatic lights and building security systems. And sensor technology will continue to grow and contribute to the modern age.

[1] M.I. Skolnik. Radar Handbook. New York: McGraw-Hill, 1990.

[2] "How PIR Motion Sensors Work". Internet: http://www.gadgetsha​ck.com/motionsensor.​html, [Nov. 10, 2007].

[3] NASA. "Cool Cosmos." Infrared Astronomy. Internet: http://coolcosmos.ip​ac.caltech.edu/cosmi​c_classroom/ir_tutor​ial/irtech.html, [Nov. 10, 2007].

[4] “Motion Sensors” Illumin, University of Southern California. Internet: http://illumin.usc.edu/printer/165/motion-sensors/ [2012]

Comments:

Michael:

Your post discussed pressure sensors that people experience every day but often overlook. I did not know the importance of pressure sensors until I read your post. And I do agree that it could be possible in the future to use the tech behind that in intelligent building design.

Audrey:

Nice introduction about the temperature sensors. You well introduced that temperature sensor has their own advantages and disadvantages. Your post is really technical and professional, but easy to read and understand.

Temperature Sensors - Group B

Temperature sensors are used in many modern day electronics to monitor heat levels to avoid overheating.  Since some processes only work within a narrow range of temperatures, accurate measurements are needed so that preventative measures can be enacted, or the system can shut down to avoid any damages.  Also, as Tyler Woyshner described in his blog post, temperature sensors are utilized in many buildings to control the comfort levels of the occupants.  He goes on to mention how measurements can be used to adjust the temperature settings of the building itself.  A variety of sensors exist including thermocouples, thermistors, sensor integrated circuits, and resistance temperature detectors (RFDs).  These are all considered contact sensors which have to touch an object to obtain a measurement.

Audrey Ryan gives a more descriptive account in her blog post about how different types of temperature sensors perform measurements, but to give a brief explanation of how these types of sensors operate, thermocouples work by having “two dissimilar metals joined together at one end, to produce a small unique voltage at a given temperature.” (Hareendran)  These types of sensors can measure a range of up to 1700 degrees but tend to not be very sensitive.  Thermistors measure a change of electrical resistance that corresponds to different temperature changes but have a smaller range of measurements and can be cheaper.  RFDs are sensors “that contain a resistor that changes resistance value as its temperature changes” (Omega) and tend to have better accuracy and stability than thermocouples. 

Temperature sensors monitor “the atomic activity and movement of an object. When temperature sensor devices read an object with zero atomic activity, the temperature point is considered absolute zero.” (DeVale)  The more atomic activity leads to higher temperatures which cause more electronic activity or resistance in the sensor taking the measurements.  Based on the strength of the temperature, the sensor can produce an analog or digital output which can be sent to databases that store measurements, or devices that display the measured temperature.

One form of non-contact temperature sensors are infrared sensors.  These “convert thermal energy sent from an object in a wavelength range of 0.7 to 20 um into an electrical signal that converts the signal for display in units of temperature after compensating for any ambient temperature. “ (Mathas)  Because these temperature measurements can be made from a distance, they are often used in hazardous environments. 

References:

Hareendran, T. K. "Working With Temperature Sensors: A Guide." Electronics Zone, 2012. Web. 18 Feb. 2014. <http://electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=1476&title%20=%20Working+With+Temperature+Sensors%3A+A+Guide&id=12364&article_type=8&b_type=new>.

Mathas, Carolyn. "Temperature Sensors; the Basics." Digi-Key Corporation, 27 Oct. 2011. Web. 18 Feb. 2014. <http://www.digikey.com/en-US/articles/techzone/2011/oct/temperature-sensors-the-basics>.

"Temperature Sensor: Understanding How They Work." DeVale Industries Inc, 2013. Web. 18 Feb. 2014. <http://www.devale.com/temperature-sensor/temperature-sensing.html>.

"What Are RTD Sensors? Why Use Them? How Do They Work?" Omega Engineering Inc, n.d. Web. 18 Feb. 2014. <http://www.omega.com/Temperature/pdf/RTD_Gen_Specs_Ref.pdf>.

Week 7 - Movement Sensors

There are many different types of movement sensors that can be used to open a door, turn on a light, flush a toilet, or most importantly protect us. Ask yourself this, when your wife tells you to pick up milk on the way home from work and you get out of the car to walk into the store, do you think about the movement sensor that opens the door for you saving you from the embarrassment of running into a door? I would say you probably don’t. This is a perfect example of how seamlessly sensors fit into our daily lives without us even thinking about how they work or what was done before them.

For store entrances, an active sensor is used to detect a change in frequencies. The high frequency sound waves are sent out, bounce off all of the surfaces, and return noticing any changes in the environment.

As everyone knows, public restrooms aren’t places people want to be touching everything in. For that reason, an infrared sensor is used to flush the toilets, turn on the faucets and the hand dryers. Infrared sensors are passive, which means that instead of emitting energy like the active sensor it detects radiation emitted by other objects. This is not only useful in public restrooms but also in the application of alarm systems, since the sensitivity can be set to the temperature of the human body thus preventing any false alarms.

Although the common uses of movement sensors were discussed, there are some very interesting ways in which movement sensors are and will be used in the future. For example, it is possible for doctors to place a movement sensor into bones during surgeries to monitor the progress of repairs. This just proves movement sensors will only continue to increase in popularity as we seek to make things more convenient and efficient.

Comments on other Posts:

Ian Lagrange de Carvalho:

Since we are both smart guys, we used the same source. This means some if not all of our content is the same. I like how you mentioned about the safety factor of motion detectors on doors whereas I was just simple focused on the convenience of them.

Teddy Bruder:

I enjoyed learning more about ultrasonic, microwave, and tomographic motion detectors because I did not touch on any of them. It was difficult for me to understand what a tomographic motion detector does so I look forward to talking in greater detail about it during class.

References

http://illumin.usc.edu/printer/165/motion-sensors/

http://security.stackexchange.com/questions/35351/what-is-the-difference-between-types-of-motion-sensors