MEASUREMENT OF TEMPERATURE
Definition temperature is a as degrees heat or cold an object, based on scale which derived from symptoms physics which can be observed. For the purposes of engineering, temperature is a measure termopotensial compared with pressure head or electrical voltage. In temperature measurement is needed its benchmark as the price basic, reference point this is needed in general for detect temperature utilized the thermal properties another of a workpiece, eg expansion properties & thermic. Because price of coefficient of expansion an ingredient are not always constant for the entire regions temperature, then the sensitivity a tool need for the calibrated for the entire range measurement.
Temperature scale that is often used is deg Celsius (0C) and deg Fahrenheid (0 F). Celsius temperature scale using the reference, and the freezing point of water vapor price of 00 and 100 0C, respectively, were Fahrenheid scale using the same reference to the price of 320 and 212 0F. Because it uses the same reference, then Darajat Fahrenheig degrees Celsius and can be converted to each other:
In the development it was found that all the molecular vibrations will stop at a certain price. In this case the price observed at -273 0C is the lowest temperature attained from practice. -273 0C temperature is used as a reference by kalvin, called the -273 0K (Calvin). Kalvin temperature called the absolute temperature, and 0K often called absolute zero temperature. Conversion between the Celsius temperature is 0K kalvin = 0C + 273.150
0F = (9/5) X (+ 320 0C) or C = (5/9) X (0F-32)
While the absolute temperature scale based Fahrenhet is Rankine :
459.690 + 0R = 0F
Temperature Gauge Principle
Temperature scale is not measured directly, the temperature measurement is always based on the physical properties of a particular object change due to the influence of temperature change. Change various objects that are used as the basic principle of a thermometer, In general there are two methods for measuring the temperature of mechanically and electronically.
Mechanical methods using sensors that respond to temperature changes with changes in the mechanical properties such as deformation of the bellows, diaphragm or Bourdon element. Method of electronically using sensors that respond to temperature changes by producing changes in electrical resistance or voltage.
Temperature scale is not measured directly, the temperature measurement is always based on the physical properties of a particular object change due to the influence of temperature change. Change various objects that are used as the basic principle of a thermometer, In general there are two methods for measuring the temperature of mechanically and electronically.
Mechanical methods using sensors that respond to temperature changes with changes in the mechanical properties such as deformation of the bellows, diaphragm or Bourdon element. Method of electronically using sensors that respond to temperature changes by producing changes in electrical resistance or voltage.
Temperature Gauge
Temperature scale is not measured directly, temperature measure is always based on the physical properties of a particular object changes due to temperature change, as changes in objects that are used as the basic principle of a thermometer, among :
1.Change object dimensions, for example:
- Thermometer in buld liquid (mercury thermometer), which is based on the principle of volume measurements in buld (expand and shrink the volume of mercury in the buld) if associated with a particular medium they want to know.
- Bimetal thermometer, based on differences in the coefficient of expansion of two different metal plates.
2. Voltage changes, based on the different nature of the two types of materials thermoelekrik (thermocouple).
3. Changes in the electrical resistance of an object, thermo resistance (PT-100).
4. Fluid pressure changes in the buld (pressure thermometer).
5. Resonasi on crystal frequency changes.
Temperature scale is not measured directly, temperature measure is always based on the physical properties of a particular object changes due to temperature change, as changes in objects that are used as the basic principle of a thermometer, among :
1.Change object dimensions, for example:
- Thermometer in buld liquid (mercury thermometer), which is based on the principle of volume measurements in buld (expand and shrink the volume of mercury in the buld) if associated with a particular medium they want to know.
- Bimetal thermometer, based on differences in the coefficient of expansion of two different metal plates.
2. Voltage changes, based on the different nature of the two types of materials thermoelekrik (thermocouple).
3. Changes in the electrical resistance of an object, thermo resistance (PT-100).
4. Fluid pressure changes in the buld (pressure thermometer).
5. Resonasi on crystal frequency changes.
Fluid in the thermometer bulb
Fluid in the buld thermometer works by:
Volume changes caused by changes tempertur, liquids contained in this buld is used to measure temperature. Where in general the volume changes that occur is small enough, then the system used in the capillary reservoir
Fluid pressure change, in which the fluid pressure detected by the pressure gauge, such as bellows and tubes Bordon.
a. Buld a fluid-filled
b. Filled System Thermometers
Limit of the measurement range is used, the point of evaporation, boiling point and freezing point fluid. But the coefficient of expansion of a fluid is not always constant between the reference point, the temperature measurement range is limited to a constant expansion properties.
Temperature measurement is strongly influenced by the "Rise time" and "settle time". Rise time and settling time is the time required to measure according to the actual temperature. One example, the mercury thermometer takes time (settling time) 3 minutes for measurement in accordance with the actual conditions.
This is caused by the transfer coefficient drawstring contact between the glass buld Dangan measured media. So that the measurement results can be observed with the fast temperature sensor required small dimensions.
Fluid in the buld thermometer works by:
Volume changes caused by changes tempertur, liquids contained in this buld is used to measure temperature. Where in general the volume changes that occur is small enough, then the system used in the capillary reservoir
Fluid pressure change, in which the fluid pressure detected by the pressure gauge, such as bellows and tubes Bordon.
a. Buld a fluid-filled
b. Filled System Thermometers
Limit of the measurement range is used, the point of evaporation, boiling point and freezing point fluid. But the coefficient of expansion of a fluid is not always constant between the reference point, the temperature measurement range is limited to a constant expansion properties.
Temperature measurement is strongly influenced by the "Rise time" and "settle time". Rise time and settling time is the time required to measure according to the actual temperature. One example, the mercury thermometer takes time (settling time) 3 minutes for measurement in accordance with the actual conditions.
This is caused by the transfer coefficient drawstring contact between the glass buld Dangan measured media. So that the measurement results can be observed with the fast temperature sensor required small dimensions.
Buld which contains the fluid
Sensitivity of the fluids can be derived as follows buld.
fluid volume change = V
V = volume of liquid in the buld
= Coefficient of expansion of fluid volume
= Change in temperature of the medium, if the change in temperatures ranging from 0, then it can be declared as a medium temperature (Ti).
Volume changes will be accommodated by the pipe capiller and observed as an increase in fluid in the pipe kapiller (x).
SAMA (Scientific Apparatur Manufactures Association) filled system thermometers split into four classes, namely:
1. Class I system, the liquid working fluid (not including mercury). Used for the measurement of temperature - 125 oF to 600 oF. Minimal span 25 oF and 450 oF maximum, as well as the order of the speed of response 5-10 seconds. Scale is uniform except at low temperatures.
2. Class II system, the working fluid in the form of steam. Used to measure the temperature of - 430 oF to 600 oF, with a minimum span of 40 oF and 300 oF maximum. scale is not uniform and the response speed of the order of 5-10 seconds.
3. Class III system, the working fluid gas. Used for temperatures from -400 oF to 1500 oF, with a minimum span of 180 oF and a maximum of 1000 oF. Uniform scale and order response time is 1-5 seconds.
4. Class IV system, the working fluid mercury. Used for temperature measurement from -40 oF to 1000 oF. Uniform scale and order response time of 4-5 seconds.
fluid volume change = V
V = volume of liquid in the buld
= Coefficient of expansion of fluid volume
= Change in temperature of the medium, if the change in temperatures ranging from 0, then it can be declared as a medium temperature (Ti).
Volume changes will be accommodated by the pipe capiller and observed as an increase in fluid in the pipe kapiller (x).
SAMA (Scientific Apparatur Manufactures Association) filled system thermometers split into four classes, namely:
1. Class I system, the liquid working fluid (not including mercury). Used for the measurement of temperature - 125 oF to 600 oF. Minimal span 25 oF and 450 oF maximum, as well as the order of the speed of response 5-10 seconds. Scale is uniform except at low temperatures.
2. Class II system, the working fluid in the form of steam. Used to measure the temperature of - 430 oF to 600 oF, with a minimum span of 40 oF and 300 oF maximum. scale is not uniform and the response speed of the order of 5-10 seconds.
3. Class III system, the working fluid gas. Used for temperatures from -400 oF to 1500 oF, with a minimum span of 180 oF and a maximum of 1000 oF. Uniform scale and order response time is 1-5 seconds.
4. Class IV system, the working fluid mercury. Used for temperature measurement from -40 oF to 1000 oF. Uniform scale and order response time of 4-5 seconds.
Pressure Thermometer
This instrument is used to measure the temperature at which glass thermometer may not be used or are away from a power source, such as the fields of oil drilling.
This instrument is used to measure the temperature at which glass thermometer may not be used or are away from a power source, such as the fields of oil drilling.
Bimetallic Thermometers
Bimetal thermometer uses the principle that the metal will expand when the temperature changes. Two metal plates (bimetal) that have different expansion coefficients used in this type of thermometer, which is fitted into a single unit. A change in temperature will cause different expansion at the plate, causing the arch
Bimetal thermometer uses the principle that the metal will expand when the temperature changes. Two metal plates (bimetal) that have different expansion coefficients used in this type of thermometer, which is fitted into a single unit. A change in temperature will cause different expansion at the plate, causing the arch
To obtain greater sensitivity, the selected materials that have a high expansion, material B ekspanpansi lower. Metallic material that is often used is invar (a mixture of iron and nickel) as a metal with a lower coefficient of expansion and brass or nickel as a metal with a higher coefficient of expansion. Brass is used at low temperatures, while nickel is used at high temperatures. Bimetel than used as a measuring tool is also used as a control element in Temperature Control System (thermostat) on the type of on-off control. Kontruksinya among others, in the form of: Spiral, U shape, Waser, helical, double helical.
Thermocouple
The working principle of the thermocouple is based on pembngkitan voltage due to temperature differences between the joints of a pair of different metals, which can be expressed mathematically by the formula:
E = μАВ (Тs - Тr).
where:
μАВ = constant termoelectrik
Тs = temperature at the sensor connection
Тr = temperature at the connection references
The working principle of the thermocouple is based on pembngkitan voltage due to temperature differences between the joints of a pair of different metals, which can be expressed mathematically by the formula:
E = μАВ (Тs - Тr).
where:
μАВ = constant termoelectrik
Тs = temperature at the sensor connection
Тr = temperature at the connection references
Materials are often used for example: Copper-Constantan (for the range - 300 to 600 oF). Chromel - Alumel (For the range -300 to 2300 oF).
At this termocople system works three kinds of effects that are interrelated:
- Seeback effect, if the temperature in both junctions are different, then there will be an electric current whose magnitude depends on the temperature difference between the two Juntion.
- Paltier effect, termocople When the electric current flowing, the temperature at Juntion will change according to the direction of power flow. The temperature at first Juntion may be higher than the medium temperature and the temperature on the other lower Juntion.
- Tamson effect, if the electric current flowing in the second thermocouple wire has gredien temperature along the wire (no drawstring flow), then the heat will be generated at any point where the direction of the electric current equal to the flow direction drawstring, and drawstring will be absorbed in the reverse direction.
Law - legal termoelectrik, can be expressed as follows :
1. Thermocouple voltage at Juntion temperatures T1 and T2 are not affected by temperature in other parts of the circuit, if the metal wire used two homogeneous.
2. If the wire is homogeneous (C) in pairs in wire A or wire B, all new Juntion have the same temperature, the voltage generated in the circuit does not change.
3. If the wire is installed on C Juntion, along AC and AB same temperature, the voltage in the circuit is not changed, the same as if the wire is not attached drawing C-4c).
4. If the AC voltage on the thermocouple is EAC, teganagan in BC is EBC thermocouple, the voltage AB is EAB = EAC + EBC (image-7.4d).
5. If the thermocouple produces a voltage E1 at Juntion temperature T1, and T2, and E2 at Juntion temperatures T2 and T3, the voltage at temperature T1 and T3 Juntion is E = E1 + E2.
At this termocople system works three kinds of effects that are interrelated:
- Seeback effect, if the temperature in both junctions are different, then there will be an electric current whose magnitude depends on the temperature difference between the two Juntion.
- Paltier effect, termocople When the electric current flowing, the temperature at Juntion will change according to the direction of power flow. The temperature at first Juntion may be higher than the medium temperature and the temperature on the other lower Juntion.
- Tamson effect, if the electric current flowing in the second thermocouple wire has gredien temperature along the wire (no drawstring flow), then the heat will be generated at any point where the direction of the electric current equal to the flow direction drawstring, and drawstring will be absorbed in the reverse direction.
Law - legal termoelectrik, can be expressed as follows :
1. Thermocouple voltage at Juntion temperatures T1 and T2 are not affected by temperature in other parts of the circuit, if the metal wire used two homogeneous.
2. If the wire is homogeneous (C) in pairs in wire A or wire B, all new Juntion have the same temperature, the voltage generated in the circuit does not change.
3. If the wire is installed on C Juntion, along AC and AB same temperature, the voltage in the circuit is not changed, the same as if the wire is not attached drawing C-4c).
4. If the AC voltage on the thermocouple is EAC, teganagan in BC is EBC thermocouple, the voltage AB is EAB = EAC + EBC (image-7.4d).
5. If the thermocouple produces a voltage E1 at Juntion temperature T1, and T2, and E2 at Juntion temperatures T2 and T3, the voltage at temperature T1 and T3 Juntion is E = E1 + E2.
Temperature Measurement Using Electrical Resistance.
The working principle is based on price changes in electrical resistance wire sensor as a result of temperature changes. in general, as the temperature rises, the price of electricity goes up detainees anyway. In the form of a mathematical relationship between the price of resistance to temperature is expressed by the formula:
Rt = Ro (1 + dt)
Where: Rt = temperautr electrical resistance at t ° C (ohm)
Ro = temperautr electrical resistivity at 0 ° C (ohm)
ð = coefficient of resistance to changes in temperature (ohm / ohm °)
Custody of a particular substance will change its temperature to change, this is the basis of the temperature detection method. Conductor materials used are metal and semi-conductor materials. Conductor material first discovered this once called RTD (resistance temperature detector).
shows the temperature curve of the resistance price. From the curves it appears that platinum has the most linear curve A platinum resistance thermometer to determine the temperature of the international standards in the region from -270 ° C to +660 ° C
The working principle is based on price changes in electrical resistance wire sensor as a result of temperature changes. in general, as the temperature rises, the price of electricity goes up detainees anyway. In the form of a mathematical relationship between the price of resistance to temperature is expressed by the formula:
Rt = Ro (1 + dt)
Where: Rt = temperautr electrical resistance at t ° C (ohm)
Ro = temperautr electrical resistivity at 0 ° C (ohm)
ð = coefficient of resistance to changes in temperature (ohm / ohm °)
Custody of a particular substance will change its temperature to change, this is the basis of the temperature detection method. Conductor materials used are metal and semi-conductor materials. Conductor material first discovered this once called RTD (resistance temperature detector).
shows the temperature curve of the resistance price. From the curves it appears that platinum has the most linear curve A platinum resistance thermometer to determine the temperature of the international standards in the region from -270 ° C to +660 ° C
Sensor element is made of a variety of forms for fluid temperature sensor, winding-resistance-wire, inserted in a stainless-steel buld to protect from liquid or ges karosif. Various plate-grid-winding terperatur used to measure the solid surface, the layer is also used to replace platinium wire windings (winding-wire).
Thermistor
First of all thermistors are made from Manganese, and Cobalt-nickel oxides, mixed in appropriate proportions and processed in the form of a backfire, then in sentring. Compared with the type conductive sensor (which has a small and positive coefficient), termister nekatif have large temperature coefficient). Thermistor type conductors is very non-linear, see Figure-7. The relationship between resistance / terperatur in the form of: R = Ro e (1 / To + 1 / T)
where:
R = Resistant thermistor at temperature T.
Ro = Hold the thermistor at temperature To.
= Constant, the characteristics of the material, K
e = exponential
T & To = the absolute temperature, K
When used to measure temperature, thermistor requires lenierisasi series, because the relationship between temperature and resistance is unbelievably not linear.
Pyrometer
Pyrometer is a temperature gauge price based radiation emitted from the heat source to be measured temperatures (such as ignition on boiler), nonkontak measuring system with a source temperature measured, where a hot objects emit heat and light kesekelilingnya, the higher terperatur objects, the more large
and the intensity of the emitted light. By measuring the amount of radiation emitted or heat or light, temperature objects can be known.
Pyrometer to determine the temperature of the object by measuring the total radiation or radiation wavelength one, on the basis of the known two kinds pyrometer, which :
- Heat radiation pyrometer Determination of temperature by measuring the total radiation emitted an object (see Figure-8). Radiation is measured with temperature sensors, such as thermocouples, thermistors.
Optical Pyrometer
Optical pyrometer using comparative methods as basic operations. In general, is taken as a reference lamp filament is electrically heated. and the temperature is obtained by comparing the size of the optical radiation from the filament and visual visual radiation from the source to be measured temperatures. There are two methods of temperature measurement of optical pyrometers premises, namely: Control the electrical current in the filament electrical resistivity rangkaian.Metode premises set this variable using the comparison lights. Optically regulator thermal radiation received by the pyrometer using several tools such as filters polarisator absorber. Optical wedge or slice daphragma. This method uses a constant intensity comparison.
Excess optical pyrometers are :
- Does not require contact with the target being measured
- Very useful for high temperature
- Accuracy is high enough
The disadvantage is :
- Relatively expensive
- In the manual type allows the emergence of operator error, nor can they be used for the measurement as a - Component of the control system.
- Measurement is affected by the material emissivity.
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