Hey all,

I have a circuit that has 11.15VDC offset which I would like to remove. The circuit is solely DC (no AC component). Someone told me I can use a voltage regulator to remove the offset therefore my read out will be between 0 - 5VDC. Can someone please shed some light on this issue.

I was thinking of using the summing opamp circuit to remove the offset. But the voltage regualtor method is interesting to me.

Furthermore, I was also thinking of having a zener diode with a avalanche voltage of 11.15V in series with a resistor and have the read out on the resistor.

Thank you,
Vinny P

 

Do you have a schematic that you could post?

.jpg or .png would be the preferred format.

 

You cannot use a typical linear regulator, since it is designed for a specific output voltage. If it were a 5V regulator, then it will not behave correctly below 5V+dropout.

It really depends on what you are driving with your intended 0-5V signal. If it is a very high impedance load, then you can use a simple voltage divider to scale your 11.15V down. If you need to drive more of a load, then you can add a voltage follower. Furthermore, if you don't want to use a voltage divider, you can set up two inverting amplifiers to give the needed gain to convert your 11.15V down to 5V. This would be a good route if your signal has a very high source impedance and if you have a bipolar supply.

Steve

 

I'm using a AD590 which will produce the current accross a load Resistor that will give the input to the ADC of an MCU.

The load accross the resistor will vary from 11.15VDC to 16.15VDC but I want it to be from 0-5VDC.

I simply want to remove the 11.15VDC offset. I beleive using an opamp it is possible (suming sircuit). However, someone did mention a voltage regualtor would be a good alternative.

Secondly I can't have a voltage divider on the 11.15VDC as I want to eliminate it completly.

Hope some one can help,
Vinny P

The following images may help.
http://img299.imageshack.us/my.php?image=2301082317qn7.jpg
http://img180.imageshack.us/my.php?image=2301082316nf6.jpg

 

Difference amplifier on first page:

http://ecow.engr.wisc.edu/cgi-bin/get/ece/340/schowalter/opampckts.pdf

11.15-16.15 signal on V2
11.15 voltage from LM317L adjustable voltage regulator on V1:

http://www.national.com/mpf/LM/LM317L.html

But for precision use an insturmentation amplifier for low loading of your signal source:

http://focus.ti.com/lit/ds/symlink/ina114.pdf

Ken

 

A summing amp would work if one used negative11.15Vdc as one i/p. A difference amp with unity gain would work with +11.15Vdc reference i/p.

All you need to know is here: http://www.allaboutcircuits.com/vol_3/chpt_8/index.html

 

Hey Guys,


I decided to use the difference amp with unity gain utilizing the LM317L op amp due to budget reasons.

Will let you know how it went.

Thank you all... it is much appreciated,
Vinny P