circuit lab therm is to rs
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Circuit Lab Therm isTRANSCRIPT
PowerPoint PresentationThermistors
THERMal resISTORS
A thermistor is a type of resistor used to measure temperature changes, relying on the change in its resistance with changing temperature. Thermistor is a combination of the words thermal and resistor. The Thermistor was invented by Samuel Ruben in 1930, and has U.S. Patent #2,021,491.
Leads, coated
Glass encased
Surface mount
Thermistors
THERMal resISTORS
Thermistors are made of semiconductor materials (metallic compounds including oxides such as manganese, copper, cobalt, and nickel, as well as single-crystal semiconductors silicon and germanium).
Contrast <<--->> Common carbon resistors, made from carbon powder mixed with a phenolic binder glue.
Leads, coated
Glass encased
Surface mount
Thermistors
THERMal resISTORS
Assume a simple linear relationship between resistance and temperature for the following discussion:
ΔR = k ΔT
Source: http://en.wikipedia.org/wiki/Thermistor
Thermistors
THERMal resISTORS
Thermistors can be classified into two types depending on the sign of k.
If k is positive, the resistance increases with increasing temperature, and the device is called a positive temperature coefficient (PTC) thermistor, Posistor.
If k is negative, the resistance decreases with increasing temperature, and the device is called a negative temperature coefficient (NTC) thermistor.
Source: http://en.wikipedia.org/wiki/Thermistor
Thermistors
THERMal resISTORS
Resistors that are not thermistors are designed to have the smallest possible k, so that their resistance remains almost constant over a wide temperature range.
Source: http://en.wikipedia.org/wiki/Thermistor
Thermistors
Source: http://www.science.uwaterloo.ca/~jddmarti/p352_w2007/Thermistor_50K.pdf
Thermistor-choice is based on the nominal resistance you want at the operating temperature range, on the size, and on the time constant.
Time constants are about 5 - 10 seconds. (Check this out with your thermistor).
Pat Arnott, ATMS 360 Atmospheric Instrumentation
Thermistors
Thermistors
THERMal resISTORS
Example Applications:
Temperature measurement.
Time delay (self heating from large current ‘opens’ the thermistor so it can be used as a slow switch). Heating = i2 R where R is the resistance and i is the current.
THERMal resISTORS
A thermistor is a type of resistor used to measure temperature changes, relying on the change in its resistance with changing temperature. Thermistor is a combination of the words thermal and resistor. The Thermistor was invented by Samuel Ruben in 1930, and has U.S. Patent #2,021,491.
Leads, coated
Glass encased
Surface mount
Thermistors
THERMal resISTORS
Thermistors are made of semiconductor materials (metallic compounds including oxides such as manganese, copper, cobalt, and nickel, as well as single-crystal semiconductors silicon and germanium).
Contrast <<--->> Common carbon resistors, made from carbon powder mixed with a phenolic binder glue.
Leads, coated
Glass encased
Surface mount
Thermistors
THERMal resISTORS
Assume a simple linear relationship between resistance and temperature for the following discussion:
ΔR = k ΔT
Source: http://en.wikipedia.org/wiki/Thermistor
Thermistors
THERMal resISTORS
Thermistors can be classified into two types depending on the sign of k.
If k is positive, the resistance increases with increasing temperature, and the device is called a positive temperature coefficient (PTC) thermistor, Posistor.
If k is negative, the resistance decreases with increasing temperature, and the device is called a negative temperature coefficient (NTC) thermistor.
Source: http://en.wikipedia.org/wiki/Thermistor
Thermistors
THERMal resISTORS
Resistors that are not thermistors are designed to have the smallest possible k, so that their resistance remains almost constant over a wide temperature range.
Source: http://en.wikipedia.org/wiki/Thermistor
Thermistors
Source: http://www.science.uwaterloo.ca/~jddmarti/p352_w2007/Thermistor_50K.pdf
Thermistor-choice is based on the nominal resistance you want at the operating temperature range, on the size, and on the time constant.
Time constants are about 5 - 10 seconds. (Check this out with your thermistor).
Pat Arnott, ATMS 360 Atmospheric Instrumentation
Thermistors
Thermistors
THERMal resISTORS
Example Applications:
Temperature measurement.
Time delay (self heating from large current ‘opens’ the thermistor so it can be used as a slow switch). Heating = i2 R where R is the resistance and i is the current.