Temperature Sensor.pdf
- 1. KATHMANDU UNIVERSITY SCHOOL OF ENGINEERING Presentation on Temperature Sensor Members Sandip Poudel Manish RC Pawan Sharma Pawan Subedi Course Instructor Anil Lamichhane 1
- 2. INTRODUCTION ● Temperature is the degree or intensity of heat present in a substance or object ● Sensor is a device that responds to a physical stimulus (such as heat, light, sound, pressure, magnetism, or a particular motion) and transmits a resulting impulse (as for measurement or operating a control) ● A thermometer is the common non electric sensor(i.e. Mechanical). ● Common electrical sensors include thermocouples, thermistors and thermopile. 2
- 3. SENSOR COVERED ● Thermocouple ● Thermistor ● Thermopile 3
- 4. THERMOCOUPLES ● It is temperature measuring instrument based on the principle of "seebeck effect". ● If both ends of the two conductors are connected and a temperature difference is maintained between the two junctions, a thermoelectric current will flow through the closed circuit (generation mode) 4
- 5. 5 THERMOCOUPLES ● If the circuit is opened an emf will appear across the open circuit (sensing mode). It is this emf that is measured in a thermocouple sensor.
- 6. Advantage and disadvantage of thermocouple ● They are simple , rugged, need no batteries, measure over very wide temperature ranges. ● The main limitation is accuracy ; system errors of less than 1c can be difficult to achieve. 6
- 7. Application These are widely used in the steel industry, heating appliances, manufacturing of electrical equipment like switch gear etc. Thermocouple are most suitable for measuring over a large temperature range, up to 1800c 7
- 8. Thermistors ● A thermistor is another special type of resistor. Its resistance changes as its temperature changes. ● When the temperature of the thermistor is low, its resistance is high. This is because a thermistor is made of a material which does not conduct electricity well at low temperatures. The outer electrons are loosely bound to the atoms and are not free to flow through the thermistor. ● As the temperature increases, more outer electrons gain enough energy to break free from atoms. The electrons are then free to flow through the thermistor 8
- 9. Thermistors ● This graph shows the thermistor's resistance against temperature. ● The resistance of the thermistor decreases as the temperature increases. ● This change in resistance according to their temperature means that thermistors can be used as temperature sensors. 9
- 10. Advantage and disadvantage of ● Thermistors, since they can be very small, are used inside many other devices as temperature sensing and correction devices. ● Thermistors typically work over a relatively small temperature range, compared to other temperature sensors, and can be very accurate and precise within that range. 10
- 11. APPLICATION OF THERMISTORS ● Thermistors can be used as current-limiting devices for circuit protection, as replacements for fuses. ● Thermistors can be used as heating elements in small temperature-controlled ovens. ● Thermistors are used as resistance thermometers in low-temperature measurements of the order of 10 K. ● Thermistors are regularly used in automotive. 11
- 12. THERMOPILE ● A thermopile is an electronic device that converts thermal energy to electrical energy. ● It is a serial-interconnected array of thermocouple, consisting of two different materials with large thermoelectric power and opposite polarities. 12
- 13. THERMOPILE ● It operate by measuring the temperature differential from their junction point to the point in which the thermocouple output voltage is measured. ● Thermopile detectors consist of array of thermocouple junctions linked in series as differential pairs. These differential pairs form the hot and cold junction. 13
- 14. ADVANTAGES ● It is non-contact based temperature sensing device which uses infrared radiation for heat transfer. ● It is used for temperature measurement of moving objects where contact based sensors are not feasible. ● It is available in smaller sizes. ● It produces larger output voltage due to use of multiple thermocouple devices. 14
- 15. APPLICATION ● Non-contact temperature measurement in the process industry ● Handheld non-contact temperature measurement ● Thermal line scanner ● Commercial building HVAC and lighting control ● Security human presence and detection 15
- 16. Thank You! Feel free to ask questions. 16