Voltage thiab tam sim no ntsuas Circuits ntawm Digital Multimeters
Ib qho digital multimeter tuaj yeem siv los ntsuas ntau yam circuits. Niaj hnub no, tus editor yuav sau ob hom kev nthuav dav: voltage thiab tam sim no ntsuas circuits. Cia wb mus saib ua ke. Cov hauv qab no tsuas yog siv rau:
1. DC tam sim no ntsuas Circuit Court hauv digital multimeter
DC tam sim no ntsuas Circuit Court yog nruab nrog 7 theem: 20 μ Ω, 200 μ Ω, 2m Ω, 20m Ω, 200m Ω, 2 Ω, thiab 20 Ω, nrog rau lub qhov hluav taws xob tshwj xeeb rau 20 Ω theem. Kev ntsuas Circuit Court yog qhia hauv daim duab. Lub diode ua haujlwm raws li kev txwv kev txwv kev tiv thaiv overvoltage, thiab 1N4148 (1 Ω / 400V) silicon yas kaw rectifier diode raug xaiv. Thaum cov input voltage qis dua qhov kev xa hluav taws xob rau pem hauv ntej ntawm Gui diode, lub diode txiav tawm thiab tsis cuam tshuam rau kev ntsuas. Thaum lub input voltage ntau tshaj 0.6 ~ 0.7V, lub diode tam sim ntawd ua, yog li limiting lub input voltage ntawm lub ntsuas. FU yog 2 Ω / 250V ceev fuse raj uas muab kev tiv thaiv overcurrent.
Ntau yam DC tam sim no ntsuas Circuit Court
R1 ~ R7 tsim ib shunt nrog tag nrho cov tsis kam ntawm 10k Ω. Ntawm lawv, R1 ~ R7 siv precision hlau zaj duab xis resistors (nrog qhov yuam kev ntawm ± 0.5%), thaum R5 thiab R6 siv precision hlau qhov txhab resistors. Vim lub siab ua hauj lwm tam sim no ntawm 20 Ω socket, ib tug manganese tooj liab hlau resistor (nrog ib tug me me kub coefficient) yog siv raws li lub shunt resistor. Nws qhov kev tiv thaiv txias yog 0.01 Ω, thiab peb tuaj yeem suav nws lub zog dissipated ntawm tag nrho cov 4W. Txij li thaum tsis muaj cov cuab yeej tiv thaiv nyob rau hauv 20 Ω ntau, nws raug pom zoo tias qhov siab tshaj plaws input tam sim no (20 Ω) ntsuas nrog qhov ntau yuav tsum tsis pub tshaj 15 vib nas this kom tsis txhob ua rau cov manganese tooj liab hlau resistor.
Piv txwv tias Im yog qhov ntau tam sim no thiab UIn yog tus nqi tag nrho ntawm cov ntsuas hluav taws xob digital input voltage, qhov tseem ceeb ntawm cov shunt resistors (sampling resistors) rau txhua lub iav tuaj yeem xam raws li cov qauv hauv qab no:
2. DC voltage ntsuas Circuit Court hauv digital multimeter
DC voltage ntau ntawm cov multimeter feem ntau yog 200mV, 2V, 20V, 200V, thiab 1000V, nrog rau cov qauv tsim ntawm 200mV. DC voltage ntsuas Circuit Court yog qhia nyob rau hauv daim duab. Ib tug precision resistor voltage divider yog tsim los ntawm R1-R5, nrog ib tug tag nrho kuj ntawm 10M Ω, uas yuav uniformly attenuate lub ntsuas DC voltage ntawm 0 mus rau 1000V mus rau hauv qab 200mV, thiab ces xa mus rau 200mV yooj yim meter rau kev ntsuas. R1-R5 txhua yam siv hlau zaj duab xis resistors nrog qhov yuam kev ntawm ± 0.5%.
DC voltage ntsuas Circuit Court
Cov ntsiab lus hauv qab no yuav tsum tau piav qhia:
① The input resistance of each voltage level is 10M Ω, considering the input resistance RIN=102 Ω=10000M Ω (typical value) of ICL7106 single-chip 31/2 bit A/D converter. When designing a multi range digital voltmeter, the input resistance RIN=0.001rIN=10M Ω of the instrument is generally selected to make RI>RIN, yog li cov nyhuv shunt ntawm RIN ntawm lub teeb liab tuaj yeem tsis quav ntsej kiag li.
② Txhawm rau txuag cov khoom hauv digital multimeters, lawv kuj tuaj yeem qiv thaum ntsuas AC voltage
Precision resistor voltage divider rau DC voltage ntau. Tsis tas li ntawd, qhov saum toj no-hais voltage divider resistor kuj ua raws li tus qauv Circuit Court rau resistor thaiv. Xav txog tias tsuas muaj 5 theem ntawm DC voltage thiab 6 theem ntawm cov resistors (200 Ω, 20k Ω, 200k Ω, 2M Ω, 20M Ω), R5 yog tiag tiag muaj li ntawm 100 Ω thiab 900 Ω resistors txuas nrog hauv series, qhov twg 100 Ω resistor tuaj yeem siv rau qib 0. (tus qauv kuj tus nqi rau qib resistor yuav tsum sib npaug rau ib nrab ntawm cov resistor ntau).
③ Vim yog qhov muaj txiaj ntsig zoo ntawm R1, txhawm rau txhawm rau txhawm rau txhawm rau ntsuas qhov ntsuas qhov tsis kam, ob qhov sib txuas ua ke feem ntau txuas rau hauv series los ua 9M Ω. Qee qhov digital multimeters kuj tseem siv lub siab ua haujlwm tsis tu ncua thiab tsis tshua muaj kev hloov kho resistor txuas nrog hauv series los ua R1.
④ Txhawm rau lim tawm cov suab nrov nrov ntawm qhov kev tawm tswv yim kawg, qee qhov digital multimeters kuj tseem txuas lub capacitor me me ntawm ntau kaum ntawm picofarads nyob rau tib lub sijhawm rau DC voltage divider.
