I have a sensor that gives me an output between 1 and 4V, and I wanted to filter out noise present on the output to give me a more stable and accurate reading.
I set up an active 2nd-order Butterworth filter using a Sallen-key topology to try to filter out any signals above ~42Hz with 0dB gain. I'm pretty sure I've constructed the circuit correctly since it's only 5 components, but the output is remaining at 2.7V regardless of input which I've been varying. What might be an issue, is that the rail to rail voltage of the op-amp is 0-5V, the same supply used for the sensors. The Op amp I'm using is an LT1013, which I've checked is a single supply op-amp.
It's been a while since I've done any analogue design, so I'm a little rusty... Any idea where my problem might lie here?
Component values R1 = 0 R2 = 10k C1 = 220nF C2 = 470nF
Sensor datasheet. From what I can gather the output impedance it 10kOhms and 20nF.
The output from the filter will feed into an ADC (MCP3202).
EDIT: I tried to take the output impedance into account, using it as my R1 value and adjusting the other component values accordingly. However the problem persists mostly, but I am now getting a very slight movement in the output, though no where near the magnitude of the input.