Fuq id-disinn u l-applikazzjoni tas-sistema tal-kejl tat-temperatura tat-termokoppja

Bħala element tipiku tal-kejl tat-temperatura, is-senser tat-termokoppja ntuża ħafna .
Din li ġejja hija sistema tipika ta 'kejl tat-temperatura kkontrollata minn mikrokompjuter ċippa waħda, li tikkonsisti fi tliet partijiet: (1) ċirkwit tal-amplifikatur tal-kejl; (2) ċirkwit ta 'konverżjoni A / D; (3) Display Circuit . Huwa użat ħafna fis-sistemi tal-kejl tat-temperatura u l-kontroll tat-temperatura fl-impjanti tal-enerġija u l-pjanti kimiċi .
1. Disinn tal-ħardwer
(1) Sensor tat-Temperatura tat-Termokoppja
Din is-sistema tuża t-termokoppji Nickel-Chromium-Nickel-Silicon . Il-firxa tat-temperatura mkejla hija 0-655 grad {. Il-kumpens tat-tarf kiesaħ jadotta l-metodu tal-pont ta 'kumpens {. il-potenzjal iġġenerat mill-pont żbilanċjat huwa użat biex jikkumpensa għall-bidla fil-bidla fit-tibdil it-termokoppja . Il-pont żbilanċjat jikkonsisti f'erba 'armi tal-pont ta' resistors r1, r2, r3 (l-istralċ tal-wajer tar-ram tal-manganiż), RCU (stralċ tal-wajer tar-ram) u regolatur tal-vultaġġ tal-pont, li huma konnessi f'serje fiċ-ċirkwit tat-termokouple . rcu u t-tarf kiesaħ ± 0 grad, u r 1= r 2= r 3=1 ω {. Il-vultaġġ tal-provvista tal-qawwa tal-pont huwa 4V, imħaddem minn provvista ta 'enerġija stabilizzata bil-vultaġġ . Rs huwa reżistenza kurrenti li tillimita l-kurrent, u l-valur tar-reżistenza tiegħu varji differenti b'valur ta' reżistenza tiegħu Thermocouples . il-pont ġeneralment ikun ibbilanċjat f'20 grad . f'dan il-ħin, l-erba 'reżistenzi tad-driegħ tal-pont tal-pont huma r {1= r {2= r {3= rcu, u m'hemm l-ebda produzzjoni fi tmiem A u B . Tqum, RCU tiżdied, filwaqt li l-potenzjal termoelettriku tat-termokoppja jonqos hekk kif it-temperatura tat-tarf kiesaħ tiżdied . UAB huwa ugwali għat-tnaqqis fil-potenzjal termoelettriku, u l-potenzjal tal-ħruġ jibqa 'mhux mibdul wara li UAB huwa sovrappost fuq il-potenzjal termoelettriku, u b'hekk jinkiseb kompless awtomatiku tal-kumpens tat-tarf kiesaħ .}}
(2) Ċirkwit tal-amplifikatur tal-kejl
Fiċ-ċirkwiti attwali, il-ħruġ tas-sinjal mit-termokoppja mhuwiex aktar minn ftit għexieren ta 'millivolti (<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.
Fiċ-ċirkwit attwali, A1 u A2 jużaw ċipep ta 'drift baxx, ta' preċiżjoni għolja op -07}, li l-input ikkumpensat Voltage Temperatura Drift Vios u l-input offset It-temperatura kurrenti IIOS huma żgħar ħafna . op {-07 juża t-teknoloġija ultra-għolja biex jagħmel it-teknoloġija tagħha Użat ħafna fl-integrazzjoni stabbli, żieda ta 'preċiżjoni, skoperta ta' paragun u amplifikazzjoni ta 'preċiżjoni ta' sinjali dgħajfa . op -07 teħtieġ provvista ta 'enerġija doppja, u l-firxa tat-temperatura operattiva hija 0-70 grad {. ġeneralment, l-aġġustament żero ma jkunx meħtieġ {{13} aġġustament. A3 uses 741 chip, which requires dual power supply, and the power supply range is ±(3-18)V. The typical power supply is ±15V, which should generally be greater than or equal to ±5V. It contains compensation capacitors inside, and no external compensation capacitors are required.
(3) Ċirkwit ta 'konverżjoni A / D (Analog-to-diġitali)
Is-sinjal tal-vultaġġ amplifikat mill-amplifikatur tal-kejl għandu firxa ta 'vultaġġ ta' 0-5 V . Dan is-sinjal huwa sinjal analogu u ma jistax jiġi aċċettat mill-kompjuter, u għalhekk konverżjoni a / d għandha titwettaq . fiċ-ċirkwit attwali, iċ-ċippa ICL710 hija magħżula . ICL7109 Low-drift, bi prezz baxx doppju-integrali 12- bit a / d konvertitur . peress li l-kurrent 12- bit suċċessiva Approssimazzjoni A / D konvertitur huwa relattivament għoli, il-veloċità rħisa {12- bit A / D il-konverter A / D A / D il-konvertitur ICL7109 Sistemi ta 'kejl ta' preċiżjoni għolja għal diversi sinjali tas-sensuri bħall-użin, il-kejl tal-pressjoni, u l-kejl tat-temperatura .
Permezz tal-analiżi ta 'hawn fuq tas-sistema ta' kejl tat-temperatura tat-termokoppja, nispera li jkun ta 'għajnuna għax-xogħol u l-istudju ta' kulħadd .