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Temperature Sensors By Grant Stucker. Brief Overview Types of Sensors and how they work Types of Sensors and how they work Sensor Applications Sensor.

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Presentation on theme: "Temperature Sensors By Grant Stucker. Brief Overview Types of Sensors and how they work Types of Sensors and how they work Sensor Applications Sensor."— Presentation transcript:

1 Temperature Sensors By Grant Stucker

2 Brief Overview Types of Sensors and how they work Types of Sensors and how they work Sensor Applications Sensor Applications Advantages and Disadvantages Advantages and Disadvantages Sensors that will work with our project Sensors that will work with our project

3 Types of Temperature Sensors Thermocouples Thermocouples Resistance Temperature Detectors (RTDs) Resistance Temperature Detectors (RTDs) Thermistors Thermistors Infrared Sensors Infrared Sensors Semiconductors Semiconductors

4 Thermocouples Two wires of different metal alloys. Two wires of different metal alloys. Converts thermal energy into electrical energy. Converts thermal energy into electrical energy. Requires a temperature difference between measuring junction and reference junction. Requires a temperature difference between measuring junction and reference junction. Easy to use and obtain. Easy to use and obtain.

5 Thermocouple Applications Plastic injection molding machinery Plastic injection molding machinery Food processing equipment Food processing equipment Deicing Deicing Semiconductor processing Semiconductor processing Heat treating Heat treating Medical equipment Medical equipment Industrial heat treating Industrial heat treating Packaging equipment Packaging equipment

6 Thermocouples Simple, Rugged High temperature operation Low cost No resistance lead wire problems Point temperature sensing Fastest response to temperature changes Least stable, least repeatable Low sensitivity to small temperature changes Extension wire must be of the same thermocouple type Wire may pick up radiated electrical noise if not shielded Lowest accuracy AdvantagesDisadvantages

7 Resistance Temperature Detectors (RTDs) Wire wound and thin film devices. Wire wound and thin film devices. Nearly linear over a wide range of temperatures. Nearly linear over a wide range of temperatures. Can be made small enough to have response times of a fraction of a second. Can be made small enough to have response times of a fraction of a second. Require an electrical current to produce a voltage drop across the sensor Require an electrical current to produce a voltage drop across the sensor

8 RTD Applications Air conditioning and refrigeration servicing Air conditioning and refrigeration servicing Furnace servicing Furnace servicing Foodservice processing Foodservice processing Medical research Medical research Textile production Textile production

9 RTDs Most stable over time Most accurate Most repeatable temperature measurement Very resistant to contamination/ corrosion of the RTD element High cost Slowest response time Low sensitivity to small temperature changes Sensitive to vibration (strains the platinum element wire) Decalibration if used beyond sensors temperature ratings Somewhat fragile AdvantagesDisadvantages

10 Thermistors A semiconductor used as a temperature sensor. Mixture of metal oxides pressed into a bead, wafer or other shape. Beads can be very small, less than 1 mm in some cases. The resistance decreases as temperature increases, negative temperature coefficient (NTC) thermistor.

11 Thermistors Most are seen in medical equipment markets. Thermistors are also used are for engine coolant, oil, and air temperature measurement in the transportation industry.

12 Thermistors High sensitivity to small temperature changes Temperature measurements become more stable with use Copper or nickel extension wires can be used Limited temperature range Fragile Some initial accuracy drift Decalibration if used beyond the sensors temperature ratings Lack of standards for replacement AdvantagesDisadvantages

13 Infrared Sensors An infrared sensor intercepts a portion of the infrared energy radiated by an object. Many types Optical Pyrometers, Radiation Pyrometers, Total Radiation Pyrometers, Automatic Infrared Thermometers, Ear Thermometers, Fiber optic Thermometers, Two-Color Pyrometers, Infra-Snakes, and many more. Many types Optical Pyrometers, Radiation Pyrometers, Total Radiation Pyrometers, Automatic Infrared Thermometers, Ear Thermometers, Fiber optic Thermometers, Two-Color Pyrometers, Infra-Snakes, and many more.

14 Infrared Applications Manufacturing process like metals, glass, cement, ceramics, semiconductors, plastics, paper, textiles, coatings. Manufacturing process like metals, glass, cement, ceramics, semiconductors, plastics, paper, textiles, coatings. Automation and feedback control Automation and feedback control Improve safety in fire-fighting, rescues and detection of criminal activities. Improve safety in fire-fighting, rescues and detection of criminal activities. Used to monitor and measure human body temperatures with one second time response. Used to monitor and measure human body temperatures with one second time response. Reliability and maintenance needs from building heating to electrical power generation and distribution Reliability and maintenance needs from building heating to electrical power generation and distribution

15 Infrared Sensors No contact with the product required Response times as fast or faster than thermocouples No corrosion or oxidation to affect sensor accuracy Good stability over time High repeatability High initial cost More complex - support electronics required Emissivity variations affect temperature measurement accuracy Field of view and spot size may restrict sensor application Measuring accuracy affected by dust, smoke, background radiation, etc. AdvantagesDisadvantages

16 Semiconductors Are small and result from the fact that semiconductor diodes have voltage-current characteristics that are temperature sensitive. Are small and result from the fact that semiconductor diodes have voltage-current characteristics that are temperature sensitive. Temperature measurement ranges that are small compared to thermocouples and RTDs, but can be quite accurate and inexpensive. Temperature measurement ranges that are small compared to thermocouples and RTDs, but can be quite accurate and inexpensive.

17 Semiconductor Applications Hard Disk Drives Hard Disk Drives Personal Computers Personal Computers Electronic Test Equipment Electronic Test Equipment Office Equipment Office Equipment Domestic Appliances Domestic Appliances Process Control Process Control Cellular Phones Cellular Phones

18 Thermal Sensor Vendors Minco Pyrotek Omega Watlow Texas Instrument National Semiconductor Maxim

19 Determining Factors Low Power Low Power Serial Interface Serial Interface Small Small Accurate Accurate Wide temperature range Wide temperature range Extras I 2 C Interface Temperature Alarms

20 Texas Instrument Specs TMP 100/101 I 2 C Interface I 2 C Interface -55º to 125ºC range -55º to 125ºC range ±1º accuracy (±3º max) ±1º accuracy (±3º max) ±0.0625ºC resolution ±0.0625ºC resolution 2.7 to 5.5 operating voltage 2.7 to 5.5 operating voltage 45 to 75 µA operating current, 0.1 to 1µA shutdown current 45 to 75 µA operating current, 0.1 to 1µA shutdown current 40ms/320ms conversion rate(9/12 bit) 40ms/320ms conversion rate(9/12 bit) 25/3 conversions per second (9/12 bit) 25/3 conversions per second (9/12 bit) Online sample request Online sample request 6 pin SO23 package 6 pin SO23 package Needs 400kHz clock for I 2 C Interface Needs 400kHz clock for I 2 C Interface

21 Maxim MAX6625/MAX6626 I 2 C Interface I 2 C Interface -55º to 125ºC range -55º to 125ºC range ±1º accuracy (±2º max) ±1º accuracy (±2º max) ±5/0.0625ºC resolution(625/626) ±5/0.0625ºC resolution(625/626) 3.0 to 5.5 operating voltage 3.0 to 5.5 operating voltage 250µA to 1mA operating current, 1µA shutdown current 250µA to 1mA operating current, 1µA shutdown current 133ms conversion rate 133ms conversion rate Online sample request Online sample request 6 pin SO23 package 6 pin SO23 package

22 National Semiconductor LM75/LM76 I 2 C Interface I 2 C Interface -55º to 125ºC range -55º to 125ºC range ±2/ ±1º accuracy ±2/ ±1º accuracy 9 bits/ 12 bits or ±0.0625ºC resolution 9 bits/ 12 bits or ±0.0625ºC resolution 3/3.3 to 5.5 operating voltage 3/3.3 to 5.5 operating voltage 0.25 to 0.5 µA operating current, 4/5µA shutdown current 0.25 to 0.5 µA operating current, 4/5µA shutdown current 100ms/400ms conversion rate(9/12 bit) 100ms/400ms conversion rate(9/12 bit) Online sample request Online sample request 8 pin SOP package 8 pin SOP package Needs 400kHz clock for I 2 C Interface Needs 400kHz clock for I 2 C Interface

23 Personal Recommendation Texas Instrument TMP100/101 Small package Can operate on lower voltage Low power consumption Accurate


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