[SOLVED] logarithmic voltage divide

[mohammadyou]

I wonder to know is there any logarithmic voltage divider?

 

[kam1787]

do you mean a voltage divider or to take logarithms? analog? digital? needs much more explanation

 

[Analog Ground]

There are logarithmic potentiometers used as panel controls. Is this what you mean?

 

[Audioguru]

Most audio volume controls are logarithmic (they are called audio taper) because our hearing's sensitivity to loudness is logarithmic.

 

[mohammadyou]

Thanks for your replies and sorry that I didn't explain it clearly. I want to sense a voltage from 10V-200V ac. the most operation voltages are around the edge (10V or around 200v) so I need to divide the voltage in order to measure it, however if I be able to use some logarithmic divider it must give me fairly accurate measurement. Am I right ?

 

[crutschow]

You can generate a logarithmic voltage from you voltage input but it requires an active logarithmic circuit. You can't do it with a passive divider circuit.

How accurately do you need to "sense" the two voltage levels? What do you want to do with the sensed signal?

 

[chuckey]

" I want to sense a voltage ", then you say "fairly accurate measurement." These are two different operations. If you want a circuit to sense 10V, you just put in some overload feature so that 200V does not blow it up. If you want to MEASURE the voltage accurately, the best thing would be an auto-ranging function, so if the input went over 11V (10V +a bit), the kit switched to 200V scaling.
Frank

 

[FvM]

It's not unusual to measure 10 to 200 V with a single range. It depends on ADC resolution and intended measurement accuracy. Otherwise you'll apply range swiitching.

 

[mohammadyou]

Thanks you guys That was amazing range switching would be best solution. but I didn't get the point of active logarithmic circuit. where can I find article about it?

 

[kam1787]

https://en.wikipedia.org/wiki/Log_amplifier

 

[mohammadyou]

https://en.wikipedia.org/wiki/Log_amplifier

) I Thought it is something special. Again thank you for your help