OP amp question
OP amp question
(OP)
I have a DC signal at 2.43V from a sensor. I want to amplify only the changes around this 2.43 signal. When the signal's not "changing" it'll go back to the level (2.43V).
I tried first with just feeding the OP with a 2.43V offset but the problem is that the original signal at 2.43 is changing over time, so after 10 min the signal rises to 2.53V och falls to 2.3V. So a fixed ofset is not desirable.
How can i change this ofset dynamicaly, so that only the changes get amplified? hope you understand my problem...
I tried first with just feeding the OP with a 2.43V offset but the problem is that the original signal at 2.43 is changing over time, so after 10 min the signal rises to 2.53V och falls to 2.3V. So a fixed ofset is not desirable.
How can i change this ofset dynamicaly, so that only the changes get amplified? hope you understand my problem...





RE: OP amp question
RE: OP amp question
RE: OP amp question
RE: OP amp question
felixc and cbarn24050, could you draw an example schematics? I'd be great. Right now i´m using the following in order to get the 2.43V signal. But i have no idea how i can continue from here.
http://hem.bredband.net/yuspoy/gif.gif
RE: OP amp question
Connect R6 to gnd instead of Vref.
The DC out value will only depend on Vref.
Calculate the RC constant. R6 x C6 to be at say ten seconds. (five times longer than the 0.5Hz period)
What is your sensor?
cbarn, what he needs is a differentiator, not an integrator.
RE: OP amp question
Of course i can change the RC constant but it will amplify the changes of the 2.43 signal. What i want is that only the changes gets amplified so that the sensor will be more sensetive.
Could you be more specific regarding the differentiator or integrator? I have no idea how this can amplify the signal...
RE: OP amp question
C6*R6= 300 milli-seconds
This gives a 0.5Hz corner frequency
(corner frequency) =1/(2*PI*C*R)
C6= 1µF
R6= 300K
is one example of a suitable pair of components in terms of time constant.
If you are using a FET input opamp then R6 =300K may be ok. If it is bipolar then R6 will need to be much lower (say 30K) making C6 10µF.
RE: OP amp question
RE: OP amp question
RE: OP amp question
Fatpo, all you need is a unity gain amplifier with a capacitive coupling at the input.
Just one opamp can make it. Bring the output to the minus input. A high-value resistor R between Vref and the plus input. A capacitor C between the plus input and your gyro. RC is your time constant, as described by logbook. Your output will be a unity-gain output, centered around the value of Vref.
I'm curious. Under which conditions did you see the gyro drift? Is it sensitive to temperature?
RE: OP amp question
Do you mean like this?
http://hem.bredband.net/yuspoy/gif2.gif
RE: OP amp question
RE: OP amp question
Out of curiosity, are you feeding the gyro out to a microcontroller? You could do all that amplifying and filtering stuff in software.