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Chapter 6Chapter 6Electrical ThermometersElectrical Thermometers
Thermocouples • Resistance Temperature Detectors (RTDs) •
Thermistors • Semiconductor Thermometers
Thermocouples • Resistance Temperature Detectors (RTDs) •
Thermistors • Semiconductor Thermometers
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
A thermocouple creates an electrical potential when the junction is at an elevated temperature.
A thermocouple creates an electrical potential when the junction is at an elevated temperature.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
The Seebeck effect causes an electrical potential when two dissimilar wires are joined and the end is heated.
The Seebeck effect causes an electrical potential when two dissimilar wires are joined and the end is heated.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
The Peltier effect can be used to build thermo-electric coolers.The Peltier effect can be used to build thermo-electric coolers.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
The Thomson effect causes heating or cooling when there is current flow through a temperature gradient in a wire.
The Thomson effect causes heating or cooling when there is current flow through a temperature gradient in a wire.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
The law of intermediate temperatures states that the temperature at the end of the wires determines the electrical potential regardless of the inter-mediate temperatures.
The law of intermediate temperatures states that the temperature at the end of the wires determines the electrical potential regardless of the inter-mediate temperatures.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
The law of inter-mediate metals states that other metals may be used in a thermocouple circuit as long as the junctions are at the same temperature.
The law of inter-mediate metals states that other metals may be used in a thermocouple circuit as long as the junctions are at the same temperature.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
A complete thermocouple circuit includes extra junctions from the copper wire in the leads to the voltmeter.
A complete thermocouple circuit includes extra junctions from the copper wire in the leads to the voltmeter.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
A 32°F ice bath is the reference temperature for thermocouple tables.
A 32°F ice bath is the reference temperature for thermocouple tables.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
An isothermal block can be used to establish a reference temperature for the cold junction.
An isothermal block can be used to establish a reference temperature for the cold junction.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
A modern digital thermo-couple system includes a voltage to temperature conversion, cold junction compensation, and a digital readout of the temperature.
A modern digital thermo-couple system includes a voltage to temperature conversion, cold junction compensation, and a digital readout of the temperature.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
Conventional thermocouple construction uses insulator beads to isolate the two thermocouple wires.Conventional thermocouple construction uses insulator beads to isolate the two thermocouple wires.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
Thermocouple designations require that the wires follow a particular voltage-temperature curve.
Thermocouple designations require that the wires follow a particular voltage-temperature curve.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
Thermocouple color codes have been standardized in many countries.
Thermocouple color codes have been standardized in many countries.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
Sheathed thermo-couples can be wired in several ways for different applications.
Sheathed thermo-couples can be wired in several ways for different applications.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
Difference thermo-couples are made of two thermocouples wired in series with reversed polarity.
Difference thermo-couples are made of two thermocouples wired in series with reversed polarity.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
A thermopile consists of several thermocouples wired in series in order to amplify the signal.
A thermopile consists of several thermocouples wired in series in order to amplify the signal.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
A swamping box uses resistors in each thermocouple circuit to eliminate errors when measuring an average reading of a set of thermocouples.
A swamping box uses resistors in each thermocouple circuit to eliminate errors when measuring an average reading of a set of thermocouples.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
A thermocouple pyrometer uses a variable potentio-meter to balance loop resistance.
A thermocouple pyrometer uses a variable potentio-meter to balance loop resistance.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
A resistance temper-ature detector (RTD) contains a resistor with a resistance that varies with temperature.
A resistance temper-ature detector (RTD) contains a resistor with a resistance that varies with temperature.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
RTDs consist of precision wires wrapped around an insulator and encapsulated in a protective sheath.
RTDs consist of precision wires wrapped around an insulator and encapsulated in a protective sheath.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
Thermistors are available in a variety of shapes and sizes.
Thermistors are available in a variety of shapes and sizes.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
The changing resistance of a thermistor can be used as a temper-ature switch.
The changing resistance of a thermistor can be used as a temper-ature switch.
Chapter 6 — Electrical ThermometersChapter 6 — Electrical Thermometers
PTC thermistors have a resistance that increases with increases in temperature.
PTC thermistors have a resistance that increases with increases in temperature.
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