O zasnovi in ​​uporabi sistema za merjenje temperature senzorjev termoelementov

Kot tipičen temperaturni merilni element je senzor termoelementov široko uporabljen .
Sledi tipičen sistem za merjenje temperature, ki ga nadzira en sam mikroračunalnik čipa, ki je sestavljen iz treh delov: (1) merilnega ojačevalnega vezja; (2) pretvorbo A/D; (3) Prikazovalno vezje . se široko uporablja v sistemih za nadzor temperature in temperature v elektrarnah in kemičnih rastlinah .
1. oblikovanje strojne opreme
(1) Senzor temperature termoelementa
This system uses nickel-chromium-nickel-silicon thermocouples. The measured temperature range is 0-655℃. The cold end compensation adopts the compensation bridge method. The potential generated by the unbalanced bridge is used to compensate for the change in thermoelectric potential caused by the change in the cold end temperature of the Termoeneryple . Neuravnoteženi most je sestavljen iz štirih mostnih rok uporov R1, R2, R3 (navijanje manganske bakrene žice), RCU (navijanje bakrene žice) in regulator napetosti mostov, ki so v serijsko povezani v termocople vezju. rcuple . rcuple . rcuple . rcuple . RCU in hladno konfli ±0℃, and R1=R2=R3=1Ω. The bridge power supply voltage is 4V, powered by a voltage-stabilized power supply. Rs is a current-limiting resistor, and its resistance value varies with different ThermoCouples . Most je običajno uravnotežen pri 20 stopinjah . V tem času so štiri mostu roke mostu mostu r 1= r 2= r3= rcu, ko je hladen del, ko se na koncu ne bo izhod, na koncu, in za primer, na koncu a in b {27} {27} {27}. se dvigne, RCU se poveča, medtem ko se termoelektrični potencial termoelementov zmanjšuje, ko se temperatura hladnega konca poveča . UAB, ki je enak zmanjšanju termoelektričnega potenciala, izhodni potencial
(2) Vezje merilnega ojačevalnika
V dejanskih vezjih izhod signala iz termoelementa ni več kot nekaj deset milivoltov (<30mV), and contains common-mode interference such as power frequency, static electricity and magnetic coupling. To amplify this kind of circuit, the amplifier circuit needs to have a high common-mode rejection ratio, high gain, low noise and high input impedance. Therefore, a measurement amplifier circuit is suitable. The measurement amplifier is also called a data amplifier, instrument amplifier and bridge amplifier. It has a high input impedance and is easy to match with various signal sources. Its input offset voltage, input offset current and input bias current are small, and the temperature drift is small. Due to the small time temperature drift, the measurement amplifier has good stability. The measurement amplifier is composed of three op amps, and the differential input terminals R1 and R2 are connected to the in-phase terminals of A1 and A2 respectively. The input impedance is very high, a symmetrical circuit structure is used, and the measured signal is directly added to the input terminal, thereby ensuring a strong ability to suppress common-mode signals. A3 is actually a differential follower, and its gain is approximately 1. The gain of the measuring amplifier is: AV=V0/(V2-V1), AV=Rf/R(1+(Rf1+Rf2)/RW). In this circuit, as long as the performance of op amps A1 and A2 is symmetrical (mainly referring to input impedance and voltage gain), their drift will be greatly reduced. They have high input impedance and common mode rejection ratio, are very sensitive to tiny differential mode voltage, and are suitable for measuring signals transmitted over long distances. Therefore, they are very easy to use with sensors with tiny outputs. RW is an external resistor used to adjust the gain, and a multi-turn potentiometer is used here.
In the actual circuit, A1 and A2 use low-drift, high-precision op amp OP-07 chips, whose input offset voltage temperature drift VIOS and input offset current temperature drift IIOS are very small. OP-07 uses ultra-high technology and "Zener fine-tuning" technology to make its VIOS, IIOS, VIOS and IIOS very small, and se široko uporablja pri stabilni integraciji, dodajanju natančnosti, primerjavi za zaznavanje in natančnosti šibkih signalov . op -07 zahteva dvojno napajanje, območje temperature obratovanja pa je 0-70 stopinja ., če je mogoče uporabiti za nič nastavitve, če ni potrebna nič nastavitve .. Prilagoditev . A3 uporablja čip 741, ki zahteva dvojno napajanje, območje napajanja pa je ± (3-18) v . Tipični napajalnik je ± 15V, ki bi moralo biti na splošno večje ali enake ± 5V {21}, ki vsebuje kompenzacijsko kapacito Zahtevano .
(3) A/D (analogno-digitalno) pretvorbo
The voltage signal amplified by the measurement amplifier has a voltage range of 0-5V. This signal is an analog signal and cannot be accepted by the computer, so A/D conversion must be performed. In the actual circuit, the ICL7109 chip is selected. ICL7109 is a high-precision, low-noise, Dvojna integral z nizkim dnom 12- bitni a/d pretvornik . Ker je trenutni 12- bitni zaporedni približek A/d pretvornik sorazmerno drag, poceni dvojni integral {15} {15} bit A/D lahko uporabimo, kot je nedvomno, kot je, da se ne pozabite, kot da se ne pozabite, kot se namen, kjer se ne more uporabljati, kot je, da se ne pozabi na sejmo Merilni sistemi z visoko natančnostjo za različne senzorske signale, kot so tehtanje, merilni tlak in merilna temperatura .
Skozi zgornjo analizo sistema merjenja temperature senzorjev termoelemente upam, da bo v pomoč pri delu in preučevanju .