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

Temperature SensorsTemperature Sensors

By Grant StuckerBy Grant Stucker

Brief OverviewBrief Overview

Types of Sensors and how they workTypes of Sensors and how they work Sensor ApplicationsSensor Applications Advantages and DisadvantagesAdvantages and Disadvantages Sensors that will work with our projectSensors that will work with our project

Types of Temperature Types of Temperature SensorsSensors

ThermocouplesThermocouples Resistance Resistance

Temperature Temperature Detectors (RTDs)Detectors (RTDs)

ThermistorsThermistors Infrared SensorsInfrared Sensors SemiconductorsSemiconductors

ThermocouplesThermocouples

Two wires of different Two wires of different metal alloys.metal alloys.

Converts thermal Converts thermal energy into electrical energy into electrical energy.energy.

Requires a temperature Requires a temperature difference between difference between measuring junction and measuring junction and reference junction.reference junction.

Easy to use and obtain.Easy to use and obtain.

Thermocouple ApplicationsThermocouple Applications

Plastic injection Plastic injection molding machinery molding machinery

Food processing Food processing equipment equipment

Deicing Deicing Semiconductor Semiconductor

processing processing Heat treating Heat treating Medical equipment Medical equipment Industrial heat treating Industrial heat treating Packaging equipment Packaging equipment

ThermocouplesThermocouples

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

AdvantagesAdvantages DisadvantagesDisadvantages

Resistance Temperature Resistance Temperature Detectors (RTDs)Detectors (RTDs)

Wire wound and thin film Wire wound and thin film devices.devices.

Nearly linear over a wide Nearly linear over a wide range of temperatures.range of temperatures.

Can be made small Can be made small enough to have enough to have response times of a response times of a fraction of a second.fraction of a second.

Require an electrical Require an electrical current to produce a current to produce a voltage drop across the voltage drop across the sensorsensor

RTD ApplicationsRTD Applications

Air conditioning and Air conditioning and refrigeration refrigeration servicing servicing

Furnace servicing Furnace servicing Foodservice Foodservice

processing processing Medical research Medical research Textile production Textile production

RTDsRTDs

► 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 sensor’s temperature ratings

► Somewhat fragile

AdvantagesAdvantages DisadvantagesDisadvantages

ThermistorsThermistors► 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.

ThermistorsThermistors

►Most are seen in medical equipment markets.

►Thermistors are also used are for engine coolant, oil, and air temperature measurement in the transportation industry.

ThermistorsThermistors

►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 sensor’s temperature ratings

► Lack of standards for replacement

AdvantagesAdvantages DisadvantagesDisadvantages

Infrared SensorsInfrared Sensors

► An infrared sensor intercepts a portion of the infrared energy radiated by an object.

► Many types Optical Pyrometers, Radiation Pyrometers, Total Many types Optical Pyrometers, Radiation Pyrometers, Total Radiation Pyrometers, Automatic Infrared Thermometers, Ear Radiation Pyrometers, Automatic Infrared Thermometers, Ear Thermometers, Fiber optic Thermometers, Two-Color Thermometers, Fiber optic Thermometers, Two-Color Pyrometers, Infra-Snakes, and many more.Pyrometers, Infra-Snakes, and many more.

Infrared ApplicationsInfrared Applications► Manufacturing process like Manufacturing process like

metals, glass, cement, metals, glass, cement, ceramics, semiconductors, ceramics, semiconductors, plastics, paper, textiles, plastics, paper, textiles, coatings.coatings.

► Automation and feedback Automation and feedback controlcontrol

► Improve safety in fire-fighting, Improve safety in fire-fighting, rescues and detection of rescues and detection of criminal activities.criminal activities.

► Used to monitor and measure Used to monitor and measure human body temperatures with human body temperatures with one second time response.one second time response.

► Reliability and maintenance Reliability and maintenance needs from building heating to needs from building heating to electrical power generation and electrical power generation and distributiondistribution

Infrared SensorsInfrared 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.

AdvantagesAdvantages DisadvantagesDisadvantages

SemiconductorsSemiconductors

►Are small and result from the fact that Are small and result from the fact that semiconductor diodes have voltage-semiconductor diodes have voltage-current characteristics that are current characteristics that are temperature sensitive. temperature sensitive.

►Temperature measurement ranges Temperature measurement ranges that are small compared to that are small compared to thermocouples and RTDs, but can be thermocouples and RTDs, but can be quite accurate and inexpensive.quite accurate and inexpensive.

Semiconductor ApplicationsSemiconductor 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

Thermal Sensor VendorsThermal Sensor Vendors

MincoMinco PyrotekPyrotek OmegaOmega WatlowWatlow Texas InstrumentTexas Instrument National SemiconductorNational Semiconductor MaximMaxim

Determining FactorsDetermining Factors

Low PowerLow Power Serial InterfaceSerial Interface SmallSmall AccurateAccurate Wide temperature Wide temperature

rangerange

ExtrasExtras II22C InterfaceC Interface Temperature AlarmsTemperature Alarms

Texas Instrument SpecsTexas Instrument SpecsTMP 100/101TMP 100/101

II22C InterfaceC 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 voltage2.7 to 5.5 operating voltage 45 to 75 µA operating 45 to 75 µA operating

current, 0.1 to 1µA current, 0.1 to 1µA shutdown currentshutdown current

40ms/320ms conversion 40ms/320ms conversion rate(9/12 bit)rate(9/12 bit)

25/3 conversions per second 25/3 conversions per second (9/12 bit)(9/12 bit)

Online sample requestOnline sample request 6 pin SO23 package6 pin SO23 package Needs 400kHz clock for INeeds 400kHz clock for I22C C

InterfaceInterface

MaximMaximMAX6625/MAX6626MAX6625/MAX6626

II22C InterfaceC Interface -55º to 125ºC range-55º to 125ºC range ±1º accuracy (±2º max)±1º accuracy (±2º max) ±5/0.0625ºC ±5/0.0625ºC

resolution(625/626)resolution(625/626) 3.0 to 5.5 operating voltage3.0 to 5.5 operating voltage 250µA to 1mA operating 250µA to 1mA operating

current, 1µA shutdown current, 1µA shutdown currentcurrent

133ms conversion rate133ms conversion rate Online sample requestOnline sample request 6 pin SO23 package6 pin SO23 package

National SemiconductorNational SemiconductorLM75/LM76LM75/LM76

II22C InterfaceC Interface -55º to 125ºC range-55º to 125ºC range ±2/ ±1º accuracy±2/ ±1º accuracy 9 bits/ 12 bits or ±0.0625ºC 9 bits/ 12 bits or ±0.0625ºC

resolutionresolution 3/3.3 to 5.5 operating voltage3/3.3 to 5.5 operating voltage 0.25 to 0.5 µA operating current, 0.25 to 0.5 µA operating current,

4/5µA shutdown current4/5µA shutdown current 100ms/400ms conversion 100ms/400ms conversion

rate(9/12 bit)rate(9/12 bit) Online sample requestOnline sample request 8 pin SOP package8 pin SOP package Needs 400kHz clock for INeeds 400kHz clock for I22C C

InterfaceInterface

Personal RecommendationPersonal Recommendation

►Texas Instrument TMP100/101Texas Instrument TMP100/101 Small packageSmall package Can operate on lower voltageCan operate on lower voltage Low power consumptionLow power consumption AccurateAccurate