Muchos lectores se sienten confundidos por los términos "lin" y "log" aplicados a los potenciómetros. En este pequeño artículo les aclaramos ei significado de estos términos, y en qué tipo de aplicaciones deben usar uno o el otro.

Es común que los principiantes se sientan confundidos cuando, al ir a adquirir un potenciômetro de determinado valor, se encuentran que para ese mismo valor existen dos posibilidades: lin o log.

¿Qué significan estos términos y de que modo hacer la elección adecuada para un proyecto?

Como seguramente ya saben, un potenciômetro es un resistor variable, o sea, un resistor cuya resistencia debe variar entre dos valores determinados cuando giramos o movemos su cursor. La resistencia presentada varia entonces entre 0 y un valor máximo que es el valor nominal del potenciômetro y por el cual lo compramos (figura 1).

 


 

 

El modo en que la resistencia varía es importante en aplicaciones determinadas, porque puede estar relacionado con la sensibilidad de nuestro oído o la presencia de una escala en el aparato.

En el caso de los potenciómetros lineales (lin), lo que ocurre es que la resistencia aumenta o varía en proporción directa al movimiento de su cursor, lo que nos lleva a una curva que justamente es una recta, como muestra la figura 2, de ahí su nombre.

 


 

 

Se puede hacer entonces una correspondencia directa de su resistencia con el ángulo de giro del potenciômetro, obteniéndose con eso una escala con divisiones iguales (figura 3).

 


 

 

En el caso de los potenciómetros logarítmicos, lo que ocurre es que la variación de la resistencia no corresponde de modo directo al movimiento del cursor, obteniéndose una curva como muestra la figura 4. Esta curva tiene su utilidad práctica.

 


 

 

Nuestro oído tiene una curva de sensibilidad no lineal, lo que quiere decir que somos más sensibles a variaciones de intensidad de un sonido de baja potencia que a un sonido de alta potencia. Por este motivo los controles de volumen de radios y amplificadores deben acompañar esta sensibilidad siendo sus potenciómetros del tipo logarítmico (log), cuya curva corresponde justamente a la respuesta de intensidad de nuestro oído.

En suma, dos potenciómetros del mismo valor, pero uno log y el otro lin presentan una variación de resistencia entre los mismos valores citados, pero el modo como ocurre esta variación es diferente.

En las aplicaciones prácticas en que el modo según el cual la resistencia varia no es importante, se puede usar tanto un potenciômetro lin como log del valor exigido.

Pero en las aplicaciones en que la curva de variación es importante, en controles de volumen de aparatos de audio o en circuitos en que existe una escala para este componente, debe ser el exigido el tipo de potenciômetro elegido.

 

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