Engineering. Whats The Difference Between Log And Reverse Log Potentiometers?

Engineering : Whats The Difference Between Log And Reverse Log Potentiometers

Can I use a log pot in place of a reverse pot? If so what would happen? ~~~ Baptiste ~~~

Best Answer To Engineering Question

They are the exact opposite. The reason for log taper or audio taper is that your ears (and other senses) operate on a log basis. If you double the sound level, say, 5 times, each change in intensity seems equal to the others. That is a log response. The log taper attempts to replicate this, so, for example, if you have a 100k pot, 1/5 of the rotation is not 2k, rather it is closer to 10 ohms. the next 1/5 of the rotation brings that up to 100 ohms, the next to 1000 ohms (1k), the next to 10000 ohms (10k), and the final segment to 100k. If the pot is used as an audio volume control, as you turn the knob clockwise the sound increases more or less following a log curve. The reverse would be totally different, as you are measuring from the other end. The first 1/5 would be 90k, the second 99k, the third 99,9k, the fourth , and the next . So all of the volume would be in the first fraction of the control, with little change in the remainder. Actually a linear taper would be better than a reverse log taper in this case. To clarify this, assume you applied 10 volts of audio signal to the top of the pot, here is what you get out from the wiper. Percent .... Log......reverse ... linear rotation .....taper ... log 0% ............. 0 v ....... 0 v ........... 0 v 20% ......... 1 mv ..... 9 v ........... 2 v 40% .........10 mv ..... v ........ 4 v 60% .......100 mv ..... + v ...... 6 v 80% ........... 1 v ........ + v ...... 8 v 100% ....... 10 v ...... 10 v ......... 10 v .

All Answer To Engineering Questions

Answer 1

You would have to wire it up to increase when turned anticlockwise for it to have the same effect as a log pot going clockwise.

Answer 2

They are the exact opposite. The reason for log taper or audio taper is that your ears (and other senses) operate on a log basis. If you double the sound level, say, 5 times, each change in intensity seems equal to the others. That is a log response. The log taper attempts to replicate this, so, for example, if you have a 100k pot, 1/5 of the rotation is not 2k, rather it is closer to 10 ohms. the next 1/5 of the rotation brings that up to 100 ohms, the next to 1000 ohms (1k), the next to 10000 ohms (10k), and the final segment to 100k. If the pot is used as an audio volume control, as you turn the knob clockwise the sound increases more or less following a log curve. The reverse would be totally different, as you are measuring from the other end. The first 1/5 would be 90k, the second 99k, the third 99,9k, the fourth , and the next . So all of the volume would be in the first fraction of the control, with little change in the remainder. Actually a linear taper would be better than a reverse log taper in this case. To clarify this, assume you applied 10 volts of audio signal to the top of the pot, here is what you get out from the wiper. Percent .... Log......reverse ... linear rotation .....taper ... log 0% ............. 0 v ....... 0 v ........... 0 v 20% ......... 1 mv ..... 9 v ........... 2 v 40% .........10 mv ..... v ........ 4 v 60% .......100 mv ..... + v ...... 6 v 80% ........... 1 v ........ + v ...... 8 v 100% ....... 10 v ...... 10 v ......... 10 v .

Answer 3

Wire it backwards to do its desired function backwards, . you turn it anticlockwise to get louder volume, then yes. Slider pots can be reversed easily by mounting them "upside down" for antilog. operation. Using a log. pot directly in place of an antilog. would probably be disastrous in audio applications, at least.