Lexicon
Absolute Seebeck Coefficient:
Specifies the differential thermoelectric voltage per K within one single homogeneous conductor that is subjected to a temperature gradient. It can only be calculated in the roundabout way using the measured values of the Thomson Effect. Reliable values exist for platinum and copper. The absolute Seebeck Coefficient is only of scientific significance.
Compensation Lead:
Signal-correct extension between the thermoelement and the measured value transducer.
In the temperature range in which it is used, the compensation lead delivers the same thermoelectric voltage, but has a completely different chemical composition than the thermoelement. The range of operating temperature is however limited. Since according to the law of linear superposition, the sum of the thermoelectric voltages in a thermoelectric measuring circuit equals the sum of many thermoelements connected in series, such a measuring circuit can also be formed from a series connection of one thermoelement and one compensation lead.
EMF (Electro Motive Force):
see Thermoelectric Voltage
Fermi, Enrico (1901 - 1954):
Italian Physicist, later naturalized in the USA.
Measuring Point:
Location of the determining temperature, at which the point of the homogeneous thermoelement comes to rest spatially and thermally.
Instrument Transformer:
Device, which can convert an input signal into another type of output signal. Frequently standardized analog output signals such as 4 ? 20 mA or 0 ? 10 V are used. More and more frequently digitized output signals such as RS232, RS485 or USB are also used.
Peltier, Jean Charles Athanase (1785 - 1845):
French Physicist; Discoverer of the Peltier Effect named after him.
Peltier Effect (1834):
If a current flows in a conductor circuit consisting of different electrical conducting materials, then the contact points are heated or cooled respectively. In its function the Peltier-Effect is thus a reversal of the Seebeck Effect.
Application: Peltier Element.
Relative Seebeck Coefficient:
Specifies the increase of the difference between the absolute Seebeck Coefficients of the two conductors per K.
Seebeck, Thomas Johann (1770 - 1831):
Physician; born in Tallin (Estonia),
later worked as physicist,
Discoverer of the Seebeck Effect named after him.
Seebeck Effect (1821):
In an electrical circuit consisting of different electrical conductors a current flows if the connection points are not at the same temperature.
Application: Thermoelement, Thermogenerator.
Seebeck Coefficient:
See Relative Seebeck Coefficient.
Temperature:
State variable, which characterizes systems in thermal balance.
Measure for the thermal state of a medium (T = Q/C).
Base quantity of the SI-System.
Is specified in K or °C.
Can be regarded as a measure for the statically determined velocity and therefore for the kinetic energy of the molecules of a medium.
Thermoelement:
A temperature sensor consisting of two different electrical conductors. Is normally made from metals. Thermoelements are the most widespread temperature-measuring medium.
Thermoelectric Power:
Product of thermoelectric current and thermoelectric voltage. Important for the transformation of energy with thermoelectric effects (Thermogenerators).
Thermal Electromotive Force:
See Relative Seebeck Coefficient
Thermoelectric Lead:
Signal-correct extension between thermoelement and measured value transducer. In the temperature range in which it is used, the thermoelectric lead delivers the same thermoelectric voltage and has the same nominal chemical composition as the thermoelement. The range of the operating temperature is however limited. Since according to the law of linear superposition, the sum of the thermoelectric voltages in a thermoelectric measuring circuit equals the sum of many thermoelements connected in series, such a measuring circuit can also be formed from a series connection of one thermoelement and one thermoelectric lead.
Thermoelectric Power: See Relative Seebeck Coefficient
Thomson, William, later Lord Kelvin (1824 - 1897):
English scientist, Discoverer of the Thomson Effect named after him.
Thomson Effect (1847):
If a current flows in a thermoelectric circuit consisting of different electrical conductors in which a temperature gradient dominates, then the individual conductors are heated or cooled respectively.
Thermoelectric Voltage:
The electric direct voltage delivered by a thermoelement. It is always a relative measure for a temperature difference and the integral of the thermal electromotive forces over the temperature difference present. The use of homogeneous thermoelements and the precise knowledge of the reference point temperature is therefore absolutely necessary.
Thermoelectric Current:
The electric current delivered by a thermoelement. Due to the high input resistances of the measuring devices, in a thermoelement measuring circuit it tends towards zero.
Reference Point:
Location of known temperature, at which the open ends of a thermoelement are connected electrically to the measuring device/the regulator. Since with thermoelements always only one temperature difference can be measured, the knowledge of the reference point temperature is absolutely necessary for the determination of the actual temperature measured.
