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circuit masurare curent

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salut,am facut un circuit care masoara impreuna cu un uC curentul care trece printr-un conductor dar am cateva probleme cu el.- ca senzor folosesc un transformator de curent Talema ASM 010 care scoate cca 30mv la10A(pe o sarcina de 50ohm eu am folosit 100ohm =Rl= );- caderea de tensiune pe =Rl= o amplific cu un amplificator lm324n cu bias/shift de 2.5v(jumatate din tensiunea max. a ADC)problema pe care o am este ca circuitul inregistreaza curent prin conductorchiar si cand nu am nici un consumator pe el. Doar cand scot de tot conductorul din senzornu mai inregistreaza nimic(linie dreapta cu ceva zgomot)Observatiile le-am facut cu osciloscopul deci nu e vb de vreo erroare in uCEu banuiesc ca e in neregula felul in care am facut bias-ul/shift-ul de 2.5v.Sper ca ma puteti ajuta cu ceva sfaturiAm atasat si schema circuitului

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Treaba asta nu o poti evita, oricum ai regla rezistentele alea vei avea un offset, care se mai si schimba functie de temperatura si alte cele. In practica se folosestie un filtru trece sus in software pentru a elimina offsetul de CC. Mai studiaza problema din app noteul de aici: http://atmel.com/dyn/resources/prod_doc ... oc2566.pdfDin docomentul cu pricina:

The first task toperform on the data is then to remove any DC offset. This is carried out using a digitalHigh-Pass Filter (HPF) of type Infinite Impulse Response (IIR).

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