Un amplificateur de mesure (en anglais Instrumentation Amplifier, in-amp ou INA) est un dispositif électronique destiné au traitement de faibles signaux électriques.

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  • Un amplificateur de mesure (en anglais Instrumentation Amplifier, in-amp ou INA) est un dispositif électronique destiné au traitement de faibles signaux électriques. On le trouve également dans la littérature sous le nom d'amplificateur d'instrumentation.L'amplificateur de mesure est un élément essentiel dans la partie de conditionnement d'une chaîne d'acquisition : il permet le traitement de signaux issus de capteurs de mesure.Il est généralement réalisé à partir d'un ou de plusieurs amplificateurs opérationnels (AOP), de telle manière qu'il améliore leurs caractéristiques intrinsèques : composante continue, dérive, bruit d'amplification, gain en boucle ouverte, taux de réjection du mode commun, impédance d'entrée.
  • Un amplificador d'instrumentació és un giny utilitzat en instrumentació electrònica per amplificar senyals molt febles que provenen de sensors, d'un pont de Wheatstone o d'altres convertidors de mesura.L'amplificador d'instrumentació pot modificar el seu guany de forma analògica (amb la variació d'una resistència externa) o de forma digital (programant un guany en funció d'entrades digitals).Els senyals d'entrada normalment poden tenir un mode diferencial i un mode comú.L'amplificador d'instrumentació està dissenyat obtenir un guany de l'entrada diferencial i reduir el màxim possible el mode comú.Amplificador d'instrumentacióLa sortida en un amplificador d'instrumentació val:Vo = Vd * Gd + Vmc * GmcEl rebuig de mode comú o CMRR és la relació entre el guany diferencial i el de mode comú i normalment s'expressa en dBCMRR= 20*log (Gd/Gmc)
  • Ein Instrumentenverstärker oder Instrumentierungsverstärker (engl. instrumentation amplifier oder InAmp) ist eine besonders präzise Operationsverstärker-Schaltung mit sehr hochohmigen (typ. 1 GΩ) Eingängen. Sie ist auch komplett als integrierter Schaltkreis mit fix eingebauten und werksseitig getrimmten Widerständen erhältlich.Instrumentenverstärker zeichnen sich durch ein besonders hohes Gleichtaktunterdrückungsverhältnis (engl.: CMRR − common mode rejection ratio) sowie geringe Eingangs-Offset-Spannungen aus.
  • An instrumentation (or instrumentational) amplifier is a type of differential amplifier that has been outfitted with input buffer amplifiers, which eliminate the need for input impedance matching and thus make the amplifier particularly suitable for use in measurement and test equipment. Additional characteristics include very low DC offset, low drift, low noise, very high open-loop gain, very high common-mode rejection ratio, and very high input impedances. Instrumentation amplifiers are used where great accuracy and stability of the circuit both short and long-term are required.Although the instrumentation amplifier is usually shown schematically identical to a standard operational amplifier (op-amp), the electronic instrumentation amp is almost always internally composed of 3 op-amps. These are arranged so that there is one op-amp to buffer each input (+,−), and one to produce the desired output with adequate impedance matching for the function.The most commonly used instrumentation amplifier circuit is shown in the figure. The gain of the circuit isThe rightmost amplifier, along with the resistors labelled and is just the standard differential amplifier circuit, with gain = and differential input resistance = 2·. The two amplifiers on the left are the buffers. With removed (open circuited), they are simple unity gain buffers; the circuit will work in that state, with gain simply equal to and high input impedance because of the buffers. The buffer gain could be increased by putting resistors between the buffer inverting inputs and ground to shunt away some of the negative feedback; however, the single resistor between the two inverting inputs is a much more elegant method: it increases the differential-mode gain of the buffer pair while leaving the common-mode gain equal to 1. This increases the common-mode rejection ratio (CMRR) of the circuit and also enables the buffers to handle much larger common-mode signals without clipping than would be the case if they were separate and had the same gain.Another benefit of the method is that it boosts the gain using a single resistor rather than a pair, thus avoiding a resistor-matching problem (although the two s need to be matched), and very conveniently allowing the gain of the circuit to be changed by changing the value of a single resistor. A set of switch-selectable resistors or even a potentiometer can be used for , providing easy changes to the gain of the circuit, without the complexity of having to switch matched pairs of resistors.The ideal common-mode gain of an instrumentation amplifier is zero. In the circuit shown, common-mode gain is caused by mismatches in the values of the equally numbered resistors and by the mis-match in common mode gains of the two input op-amps. Obtaining very closely matched resistors is a significant difficulty in fabricating these circuits, as is optimizing the common mode performance of the input op-amps.An instrumentation amp can also be built with two op-amps to save on cost and increase CMRR, but the gain must be higher than two (+6 dB).Instrumentation amplifiers can be built with individual op-amps and precision resistors, but are also available in integrated circuit form from several manufacturers (including Texas Instruments, National Semiconductor, Analog Devices, Linear Technology and Maxim Integrated Products). An IC instrumentation amplifier typically contains closely matched laser-trimmed resistors, and therefore offers excellent common-mode rejection. Examples include AD8221, MAX4194, LT1167 and INA128.Instrumentation Amplifiers can also be designed using "Indirect Current-feedback Architecture", which extend the operating range of these amplifiers to the negative power supply rail, and in some cases the positive power supply rail. This can be particularly useful in single-supply systems, where the negative power rail is simply the circuit ground (GND). Examples of parts utilizing this architecture are MAX4208/MAX4209 and AD8129/AD8130.Feedback-free instrumentation amplifier is the high input impedance differential amplifier designed without the external feedback network. This allows reduction in the number of amplifiers (one instead of three), reduced noise (no thermal noise is brought on by the feedback resistors) and increased bandwidth (no frequency compensation is needed). Chopper stabilized (or zero drift) instrumentation amplifiers such as the LTC2053 use a switching input front end to eliminate DC offset errors and drift.
  • Un amplificador de instrumentación es un dispositivo creado a partir de amplificadores operacionales. Está diseñado para tener una alta impedancia de entrada y un alto rechazo al modo común (CMRR). Se puede construir a base de componentes discretos o se puede encontrar encapsulado (por ejemplo el INA114).La operación que realiza es la resta de sus dos entradas multiplicada por un factor.Su utilización es común en aparatos que trabajan con señales muy débiles, tales como equipos médicos (por ejemplo, el electrocardiógrafo), para minimizar el error de medida.
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prop-fr:année
  • 1996 (xsd:integer)
prop-fr:auteurs
  • Paul Horowitz, Winfield Hill
prop-fr:isbn
  • 978 (xsd:integer)
  • 2866610709 (xsd:double)
prop-fr:langue
  • fr
prop-fr:titre
  • Traité de l’électronique analogique et numérique
prop-fr:titreOriginal
  • The Art of Electronics
prop-fr:titreVolume
  • Techniques analogiques
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  • 1 (xsd:integer)
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  • Elektor
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rdfs:comment
  • Un amplificateur de mesure (en anglais Instrumentation Amplifier, in-amp ou INA) est un dispositif électronique destiné au traitement de faibles signaux électriques.
  • Un amplificador d'instrumentació és un giny utilitzat en instrumentació electrònica per amplificar senyals molt febles que provenen de sensors, d'un pont de Wheatstone o d'altres convertidors de mesura.L'amplificador d'instrumentació pot modificar el seu guany de forma analògica (amb la variació d'una resistència externa) o de forma digital (programant un guany en funció d'entrades digitals).Els senyals d'entrada normalment poden tenir un mode diferencial i un mode comú.L'amplificador d'instrumentació està dissenyat obtenir un guany de l'entrada diferencial i reduir el màxim possible el mode comú.Amplificador d'instrumentacióLa sortida en un amplificador d'instrumentació val:Vo = Vd * Gd + Vmc * GmcEl rebuig de mode comú o CMRR és la relació entre el guany diferencial i el de mode comú i normalment s'expressa en dBCMRR= 20*log (Gd/Gmc)
  • Un amplificador de instrumentación es un dispositivo creado a partir de amplificadores operacionales. Está diseñado para tener una alta impedancia de entrada y un alto rechazo al modo común (CMRR).
  • An instrumentation (or instrumentational) amplifier is a type of differential amplifier that has been outfitted with input buffer amplifiers, which eliminate the need for input impedance matching and thus make the amplifier particularly suitable for use in measurement and test equipment. Additional characteristics include very low DC offset, low drift, low noise, very high open-loop gain, very high common-mode rejection ratio, and very high input impedances.
  • Ein Instrumentenverstärker oder Instrumentierungsverstärker (engl. instrumentation amplifier oder InAmp) ist eine besonders präzise Operationsverstärker-Schaltung mit sehr hochohmigen (typ. 1 GΩ) Eingängen.
rdfs:label
  • Amplificateur de mesure
  • Amplificador d'instrumentació
  • Amplificador de instrumentación
  • Amplificatore da strumentazione
  • Instrumentation amplifier
  • Instrumentazioko anplifikadore
  • Instrumentenverstärker
  • Измерительный усилитель
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