<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="font-family: "Arial","sans-serif"; font-size: 10pt; mso-fareast-font-family: 'Times New Roman';">Priklad rekneme, ze na zacatku toho celeho je zdroj proudu, ktery aktualne dava AC 10uA s DC posunem 1A, tedy v realu jde o DC zdroj 1A ktery ma zvlneni 10uA, frekvence zvlneni je treba 10kHz (nevyhlazena cast z spinaneho zdroje).<br />
Pokud budeme proud merit na odporu pomoci ADC tak at budeme merit sebepecliveji tak zvlneni je o pet radu nize nez DC proud (1A : 10uA). Druhy problemje frekvenze vlneni, uz pri 10kHz bychom potrebovali ADC s placnu 50k SPS a s presnosti , ktera postihne uA na A.<br />
Proto DC slozku merime klasicky na bocniku a za to osadime proudove trafo s kondenzatorem na vstupu. C (100nF) oddeli DC a AC, do trafa tedy vstupuje pouze 10uA , ktere pri prevodnim pomeru 1:1vyvola na sekundaru 10uA jiz bez "parazitni" DC slozky (idealni trafo).<br />
Na sekundar tedy osadime proudovy zesilovac, ktery zesili proud x krat, respektiuve ho prevede na napeti, napeti nasledne budeme nejak integrovat v case. Cili nakonci mame napeti ktere je primo umerne sume AC slozky obsazene v proudu a kdyz nasledne sectema Idc+Iac mame hodnotu proudu, ktera vice odpovida hodnote proudu zdrojem nez ciste DC slozka DC odmerena na bocniku + mame kvantifikovane zvlneni. Abychom postihli co nejsirsi cast AC slozek proudu , pouzijeme sirokopasmovy zesilovac.<br />
<br />
Az sem to mam teoreticky zmaknute. Prakticky realizovatelne to je take (viz muj pristroj), respektive podobne fungujici proudova trafa se pouzivaji u osciloskopu k mereni proudu a tam se pracuje i se stovkami MHz a pA.<br />
Nicmene. Prakticka realizace mi je zahadou.<br />
Trafo, z jakeho materilalu ma byt jadro, aby ztraty v jadre nebyly vetsi nez mg. sila vybuzena timto pidi proudem, kolik zavitu , rucne se neda na toroid namotat vice nez radove sto na kazde strane.<br />
Zesilovac, jak balu poznamenal, vstupy nutne nemusi byt vuci zemi, ale to pak pracuje s napetimi na vstupu a tohle by mel byt zesilovac proudu , jak z logiky veci, tak popisu, ktery u toho je v blokovem schematku a tam mi u klasickeho zesilovace neni tak uplne jasne kam proud tece. Jsem zvykly na zesilovace proudu v invertujicicm provedeni, kde proud "tece" do vystupu viz treba zde, strana 20 <a href="http://focus.ti.com/lit/an/sboa092a/sboa092a.pdf">http://focus.ti.com/lit/an/sboa092a/sboa092a.pdf</a>. Takhle pri komparaci napeti na vstupech bude stejne litat napeti na vystupu v mezich napajeciho napeti OZ , ale nebude to snad zesilovat proud?<br />
Napadlo me zda to nemuze byt zesilovac s proudovou zpetnou vazbou, ale o tom vim uz uplny kukovy.<br />
<br />
Pavel<br />
<br />
>Podla mna OZ je zapojeny ako "detektor polarity napatia z transformatora s hystereziou". Cele to to asi detekuje pokles alebo narast DC.</span><span style="mso-fareast-font-family: 'Times New Roman';"></span></p>
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<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="font-family: "Arial","sans-serif"; font-size: 10pt; mso-fareast-font-family: 'Times New Roman';">Milan</span><span style="mso-fareast-font-family: 'Times New Roman';"></span></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="font-family: "Arial","sans-serif"; font-size: 10pt; mso-fareast-font-family: 'Times New Roman';">----- Original Message ----- </span></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt; background: #e4e4e4;"><strong><span style="font-family: "Arial","sans-serif"; font-size: 10pt; mso-fareast-font-family: 'Times New Roman';">From:</span></strong><span style="font-family: "Arial","sans-serif"; font-size: 10pt; mso-fareast-font-family: 'Times New Roman';"> <a href="mailto:dracek.fracek@gmail.com"><font color="#0000ff">Draček Fráček</font></a> </span></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><strong><span style="font-family: "Arial","sans-serif"; font-size: 10pt; mso-fareast-font-family: 'Times New Roman';">To:</span></strong><span style="font-family: "Arial","sans-serif"; font-size: 10pt; mso-fareast-font-family: 'Times New Roman';"> <a href="mailto:hw-list@list.hw.cz"><font color="#0000ff">hw-list@list.hw.cz</font></a> </span></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><strong><span style="font-family: "Arial","sans-serif"; font-size: 10pt; mso-fareast-font-family: 'Times New Roman';">Sent:</span></strong><span style="font-family: "Arial","sans-serif"; font-size: 10pt; mso-fareast-font-family: 'Times New Roman';"> Thursday, September 23, 2010 8:51 AM</span></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><strong><span style="font-family: "Arial","sans-serif"; font-size: 10pt; mso-fareast-font-family: 'Times New Roman';">Subject:</span></strong><span style="font-family: "Arial","sans-serif"; font-size: 10pt; mso-fareast-font-family: 'Times New Roman';"> Re: Mereni proudu - co je to zac?</span></p>
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<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><font size="3"><span style="font-family: "Courier New"; mso-fareast-font-family: 'Times New Roman';">Koukal jsme se na zapojeni a neni mi jasna funkce zesilovace, </span><span style="mso-fareast-font-family: 'Times New Roman';"></span></font></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><font size="3"><span style="font-family: "Courier New"; mso-fareast-font-family: 'Times New Roman';">vzdyt ani jeden z vstupu neni vstazen k zemi? </span><span style="mso-fareast-font-family: 'Times New Roman';"></span></font></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><font size="3"><span style="font-family: "Courier New"; mso-fareast-font-family: 'Times New Roman';">Jak a co vlastne zesiluje?</span><span style="mso-fareast-font-family: 'Times New Roman';"></span></font></p>
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<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><font size="3"><span style="font-family: "Courier New"; mso-fareast-font-family: 'Times New Roman';">Martin</span><span style="mso-fareast-font-family: 'Times New Roman';"></span></font></p>
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<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><font size="3"><span style="font-family: "Courier New"; mso-fareast-font-family: 'Times New Roman';">---------------------------------------- + DC</span><span style="mso-fareast-font-family: 'Times New Roman';"></span></font></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><font size="3"><span style="font-family: "Courier New"; mso-fareast-font-family: 'Times New Roman';"> | _______</span><span style="mso-fareast-font-family: 'Times New Roman';"></span></font></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><font size="3"><span style="font-family: "Courier New"; mso-fareast-font-family: 'Times New Roman';"> | _______| |____</span><span style="mso-fareast-font-family: 'Times New Roman';"></span></font></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><font size="3"><span style="font-family: "Courier New"; mso-fareast-font-family: 'Times New Roman';"> ---- | |______| |</span><span style="mso-fareast-font-family: 'Times New Roman';"></span></font></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><font size="3"><span style="font-family: "Courier New"; mso-fareast-font-family: 'Times New Roman';"> ---- C ______ | |</span><span style="mso-fareast-font-family: 'Times New Roman';"></span></font></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><font size="3"><span style="font-family: "Courier New"; mso-fareast-font-family: 'Times New Roman';"> | _____| |__|__ | |</span><span style="mso-fareast-font-family: 'Times New Roman';"></span></font></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><font size="3"><span style="font-family: "Courier New"; mso-fareast-font-family: 'Times New Roman';"> | | ( |______| |+ |</span><span style="mso-fareast-font-family: 'Times New Roman';"></span></font></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><font size="3"><span style="font-family: "Courier New"; mso-fareast-font-family: 'Times New Roman';"> )| ( | ____________|______</span><span style="mso-fareast-font-family: 'Times New Roman';"></span></font></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><font size="3"><span style="font-family: "Courier New"; mso-fareast-font-family: 'Times New Roman';"> | | (___________________|- /</span><span style="mso-fareast-font-family: 'Times New Roman';"></span></font></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><font size="3"><span style="font-family: "Courier New"; mso-fareast-font-family: 'Times New Roman';"> | | /</span><span style="mso-fareast-font-family: 'Times New Roman';"></span></font></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><font size="3"><span style="font-family: "Courier New"; mso-fareast-font-family: 'Times New Roman';"> | |/</span><span style="mso-fareast-font-family: 'Times New Roman';"></span></font></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><font size="3"><span style="font-family: "Courier New"; mso-fareast-font-family: 'Times New Roman';">---------------------------------------- - DC</span><span style="mso-fareast-font-family: 'Times New Roman';"></span></font></p>
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<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="mso-fareast-font-family: 'Times New Roman';"><font size="3"><font face="Times New Roman">>Vazba je spravne, tedy kladna, ale rozhodne to neni obvod pro detekci zapnuti, jak zde jiz zaznelo, na to je v tomto obvodu vlozeno moc penez, sirokopasmovy zesilovac a i to trafo vypada moc radiometricky (draze). Zda je ze zdroje odebiran proud poznam lepe a levneji na mericich odporech.</font></font></span></p>
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<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="mso-fareast-font-family: 'Times New Roman';"><font size="3"><font face="Times New Roman">>Pokud máte správně namalované + a - vstupy OZ, tak OZ má kladnou zpětnou vazbu. Myslím že by to mohl být třeba obvod pro detekci nabíjení toho kondenzátoru, tzn. zapnutí celého obvodu?</font></font></span></p>
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<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="mso-fareast-font-family: 'Times New Roman';"><font size="3"><font face="Times New Roman">Nahledl jsem do programovaciho manualu a asi nasel dasi voditko, v casti programovani zdroje proudu se pise, ze lze zvolit typ detektoru proudu a to ACDC a ciste DC.</font></font></span></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="mso-fareast-font-family: 'Times New Roman';"><font size="3"><font face="Times New Roman">pricemz prefered je ACDC, ktery je preferovany pri mereni dynamickych deju eliminuje kapacitu vzorku a umoznuje detekci pulsu a dalsich zvlneni s frekvenci vyssi nez nekolik kHz. Tim asi autor mysli, vetsi nez je frekvence postizitelna samplovanim ADC.</font></font></span></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="mso-fareast-font-family: 'Times New Roman';"><font size="3"><font face="Times New Roman">Ucel je asi odhalen, ted nastupuje matematicka analyza :-)</font></font></span></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="mso-fareast-font-family: 'Times New Roman';"><font size="3"><font face="Times New Roman">V rezimu ACDC se tedy nejspise meri na odporu a pak se prepne na vystup OZ za trafem a domeri se AC slozka.</font></font></span></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="mso-fareast-font-family: 'Times New Roman';"><font size="3"><font face="Times New Roman">Zesilovac sice primarne neni zakreslen jako integracni, ale nekde tam nejaky integracni clanek byt musi.</font></font></span></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="mso-fareast-font-family: 'Times New Roman';"><font size="3"><font face="Times New Roman">Rekneme, ze trafo je 1:1000, stejny bude i pomer proudu mezi primarem a sekundarem. Z proudu na sec. udelame na R napeti to zesilime a pripadne zintegrujeme na</font></font></span></p>
<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="mso-fareast-font-family: 'Times New Roman';"><font size="3"><font face="Times New Roman">zesilovaci a na ADC mame nejaka data. Az sem jasne, jaky je ale pomer mezi proudem primarem a zvlnenim proudu na vzorku (pripominam vazba je pouze kapacitni, proud pres trafo neprochazi?</font></font></span></p>
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<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="mso-fareast-font-family: 'Times New Roman';"><font size="3"><font face="Times New Roman">Pavel</font></font></span></p>
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<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="mso-fareast-font-family: 'Times New Roman';"><font size="3"><font face="Times New Roman">>Akurat, ze to I nie je prud v tych "vodorovnych" drotoch, ale prud primarom trafa, no a to je zavisle od zmeny napatia medzi vodorovnymi drotmi (ako presne to zavisi od hodnot C a L). Prud sa bez vlozenia "niecoho" do meraneho obvodu zmerat neda.</font></font></span></p>