Un voltímetro es un instrumento que sirve para medir la diferencia de potencial entre dos puntos de un circuito eléctrico.
Contenido[ocultar] |
[editar]Clasificación
Podemos clasificar los voltímetros por los principios en los que se basa su funcionamiento.
[editar]Voltímetros electromecánicos
Estos voltímetros, en esencia, están constituidos por un galvanómetro cuya escala ha sido graduada en voltios. Existen modelos para corriente continua y paracorriente alterna.
[editar]Voltímetros electrónicos
Añaden un amplificador para proporcionar mayor impedancia de entrada (del orden de los 20 mega ohmios) y mayor sensibilidad. Algunos modelos ofrecen medida de "verdadero valor eficaz" para corrientes alternas. Los que no miden el verdadero valor eficaz es porque miden el valor de pico a pico, y suponiendo que se trata de una señal sinusoidal perfecta, calculan el valor eficaz por medio de la siguiente fórmula:
[editar]Voltímetros vectoriales
Se utilizan con señales de microondas. Además del módulo de la tensión dan una indicación de su fase. Se usa tanto por los especialistas y reparadores de aparatos eléctricos, como por aficionados en el hogar para diversos fines; la tecnología actual ha permitido poner en el mercado versiones económicas y al mismo tiempo precisas para el uso general. Son dispositivos presentes en cualquier casa de ventas dedicada a la electrónica.
[editar]Voltímetros digitales
Dan una indicación numérica de la tensión, normalmente en una pantalla tipo LCD. Suelen tener prestaciones adicionales como memoria, detección de valor de pico, verdadero valor eficaz (RMS), autorrango y otras funcionalidades.
El sistema de medida emplea técnicas de conversión analógico-digital (que suele ser empleando un integrador de doble rampa) para obtener el valor numérico mostrado en una pantalla numérica LCD.
El primer voltímetro digital fue inventado y producido por Andrew Kay de "Non-Linear Systems" (y posteriormente fundador de Kaypro) en 1954.
[editar]Utilización
Para efectuar la medida de la diferencia de potencial el voltímetro ha de colocarse en paralelo; esto es, en derivación sobre los puntos entre los que tratamos de efectuar la medida. Esto nos lleva a que el voltímetro debe poseer una resistencia interna lo más alta posible, a fin de que no produzca un consumo apreciable, lo que daría lugar a una medida errónea de la tensión. Para ello, en el caso de instrumentos basados en los efectos electromagnéticos de la corriente eléctrica, estarán dotados de bobinas de hilo muy fino y con muchas espiras, con lo que con poca intensidad de corriente a través del aparato se consigue el momento necesario para el desplazamiento de la aguja indicadora.
En la actualidad existen dispositivos digitales que realizan la función del voltímetro presentando unas características de aislamiento bastante elevadas empleando complejos circuitos de aislamiento.
En la Figura 1 se puede observar la conexión de un voltímetro (V) entre los puntos de a y b de un circuito, entre los que queremos medir su diferencia de potencial.
En algunos casos, para permitir la medida de tensiones superiores a las que soportarían los devanados y órganos mecánicos del aparato o los circuitos electrónicosen el caso de los digitales, se les dota de una resistencia de elevado valor colocada en serie con el voltímetro, de forma que solo le someta a una fracción de la tensión total.
A continuación se ofrece la fórmula de cálculo de la resistencia serie necesaria para lograr esta ampliación o multiplicación de escala:
,
donde N es el factor de multiplicación (N≠1)
Ra es la Resistencia de ampliación del voltímetro
Rv es la Resistencia interna del voltímetro
Ra es la Resistencia de ampliación del voltímetro
Rv es la Resistencia interna del voltímetro
A voltmeter is an instrument that measures the potential difference between two points in an electrical circuit.Contents [hide]1 Classification1.1 Electromechanical Voltmeters1.2 Electronic Voltmeters1.3 Vector Voltmeters1.4 Digital Voltmeters2 Use3 See also[Edit] Classification
We can classify the voltmeters for the principles underlying its operation.[Edit] Electromechanical VoltmetersThese voltmeters essentially consist of a galvanometer whose scale is graduated in volts. There are models for DC and AC paracorriente.[Edit] Electronic VoltmetersAdding an amplifier to provide increased input impedance (of the order of 20 mega ohms) and increased sensitivity. Some models offer a measure of "true RMS" for alternating currents. Those who do not measure the true RMS value is measured as peak to peak, and assuming that this is a perfect sine wave, the rms value calculated by the following formula:
[Edit] Vector VoltmetersUsed with microwave signals. Furthermore the voltage module give an indication of its phase. It is used both by specialists and repair of electrical, for fans at home for various purposes, the current technology has led to market economic versions while accurate for general use. Devices are present in any sales house dedicated to electronics.[Edit] Digital VoltmetersGiving a numerical indication of the voltage, typically an LCD display. They often have additional features such as memory, peak value detection, True RMS (RMS), autoranging and other features.The measurement system employs techniques analog-digital conversion (usually employing a dual-slope integrator) to obtain the numerical value shown in an LCD numerical display.The first digital voltmeter was invented and produced by Andrew Kay of "Non-Linear Systems" (and later founder of Kaypro) in 1954.[Edit] Uses
To effect the measurement of the voltmeter potential difference has to be placed in parallel, ie, in shunt on the points between which try to perform the measurement. This leads to the voltmeter must have an internal resistance as high as possible, so that does not produce an appreciable consumption, which would lead to an erroneous measurement of the voltage. For this, in the case of instruments based on the electromagnetic effects of electric current will be provided with very fine wire coils and with many turns, so that low current through the apparatus is achieved when needed for the movement of the pointer.
Figure 1. - Connect a voltmeter to a circuitAt present there are devices that perform digital voltmeter function presenting a fairly high isolation characteristics using complex isolation circuits.Figure 1 shows the connection of a voltmeter (V) between the points a and b of a circuit to be measured between the potential difference.In some cases, to allow measurement of voltages higher than those that would support the windings and mechanical parts of the apparatus or circuitry electrónicosen the case of digital gives them a high value resistor placed in series with the voltmeter, so will undergo only a fraction of the total voltage.Here's the formula for calculating the series resistance required to achieve this expansion or multiplication of scale:,where N is the multiplication factor (N ≠ 1)Ra is the resistance of the voltmeter expansionRv is the internal resistance of the voltmeter
We can classify the voltmeters for the principles underlying its operation.[Edit] Electromechanical VoltmetersThese voltmeters essentially consist of a galvanometer whose scale is graduated in volts. There are models for DC and AC paracorriente.[Edit] Electronic VoltmetersAdding an amplifier to provide increased input impedance (of the order of 20 mega ohms) and increased sensitivity. Some models offer a measure of "true RMS" for alternating currents. Those who do not measure the true RMS value is measured as peak to peak, and assuming that this is a perfect sine wave, the rms value calculated by the following formula:
[Edit] Vector VoltmetersUsed with microwave signals. Furthermore the voltage module give an indication of its phase. It is used both by specialists and repair of electrical, for fans at home for various purposes, the current technology has led to market economic versions while accurate for general use. Devices are present in any sales house dedicated to electronics.[Edit] Digital VoltmetersGiving a numerical indication of the voltage, typically an LCD display. They often have additional features such as memory, peak value detection, True RMS (RMS), autoranging and other features.The measurement system employs techniques analog-digital conversion (usually employing a dual-slope integrator) to obtain the numerical value shown in an LCD numerical display.The first digital voltmeter was invented and produced by Andrew Kay of "Non-Linear Systems" (and later founder of Kaypro) in 1954.[Edit] Uses
To effect the measurement of the voltmeter potential difference has to be placed in parallel, ie, in shunt on the points between which try to perform the measurement. This leads to the voltmeter must have an internal resistance as high as possible, so that does not produce an appreciable consumption, which would lead to an erroneous measurement of the voltage. For this, in the case of instruments based on the electromagnetic effects of electric current will be provided with very fine wire coils and with many turns, so that low current through the apparatus is achieved when needed for the movement of the pointer.
Figure 1. - Connect a voltmeter to a circuitAt present there are devices that perform digital voltmeter function presenting a fairly high isolation characteristics using complex isolation circuits.Figure 1 shows the connection of a voltmeter (V) between the points a and b of a circuit to be measured between the potential difference.In some cases, to allow measurement of voltages higher than those that would support the windings and mechanical parts of the apparatus or circuitry electrónicosen the case of digital gives them a high value resistor placed in series with the voltmeter, so will undergo only a fraction of the total voltage.Here's the formula for calculating the series resistance required to achieve this expansion or multiplication of scale:,where N is the multiplication factor (N ≠ 1)Ra is the resistance of the voltmeter expansionRv is the internal resistance of the voltmeter
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