Uvod u termoelemente i principe mjerenja temperature

1, Uvod u termoelemente
Termoelektrični registratori temperature često koriste termoelemente kao elemente za mjerenje temperature. Oni se široko koriste za mjerenje temperatura u rasponu od -200 stepeni do 1300 stepeni. U posebnim slučajevima mogu mjeriti visoke temperature do 2800 stepeni ili niske temperature do 4K. Imaju karakteristike jednostavne strukture, niske cijene, visoke preciznosti i širokog raspona mjerenja temperature. Zbog termoparova koji pretvaraju temperaturu u električnu energiju za detekciju, mjerenje temperature, kontrolu i pojačavanje i transformaciju temperaturnih signala su vrlo zgodni, pogodni za mjerenje na velikim udaljenostima i automatsku kontrolu. U metodi kontaktnog mjerenja temperature rasprostranjena je primjena termoelektričnih termometara.
2, princip mjerenja temperature termoelementom:
Definition: A sensor composed of two conductors that converts temperature into thermoelectric electromotive force is called a thermocouple. 2. Temperature measurement principle: The temperature measurement principle of a thermocouple is based on the thermoelectric effect. Two different materials of conductors A and B are connected in series to form a closed circuit. When the temperatures of contact 1 and 2 are different, if T>T0 (as shown in Figure 12-1 thermoelectric effect), a thermoelectric electromotive force will be generated in the circuit, and a certain amount of current will be generated in the circuit. This phenomenon is called thermoelectric effect. The thermoelectric electromotive force is denoted as EAB, and conductors A and B are called thermoelectric electrodes. Contact 1 is usually welded together and placed in a temperature measuring location to sense the measured temperature, hence it is called the measuring end (or working end, hot end). Contact 2 requires a constant temperature and is called the reference end (or cold end). 3. Thermoelectric effect: The closed circuit of a thermocouple composed of conductors A and B has two contact potentials, eAB (T) and eAB (T0), respectively, at the two junctions. Additionally, because T>T{{0}}, postoji potencijal temperaturne razlike u provodnicima A i B. Dakle, ukupna termoelektrična elektromotorna sila EAB (T, T0) zatvorenog kola treba da bude algebarski zbir kontaktna elektromotorna sila i elektromotorna sila temperaturne razlike, odnosno 4. Za odabrani termoelement, kada je referentna temperatura konstantna, ukupna termoelektrična elektromotorna sila postaje funkcija jedne vrijednosti krajnje temperature mjerenja T, odnosno EAB ( T, T0)=f (T). Ovo je osnovni princip mjerenja temperature pomoću termoparova. U stvarnom mjerenju temperature potrebno je uvesti spojne žice i instrumente u zatvorenu petlju termoelementa.