I have a good understanding of circuit theory, but only a few large projects under my belt. In practical applications, at what voltage level does noise really become an issue.
Is there any 'typical' white noise level in circuits (e.g. 100mVpp can be expected in most circuits).
I am building a current sensor circuit with just a basic series resistor. I am going to measure the voltage drop across it to determine the current. Let's say I was going to measure 150V supply current. If I use a 0.1 ohm resistor in-line, and expect 10 Amps, that would be a 1V drop and 10W dissipated power. If I use a 0.01 resistor, I get only 1W of dissipated power, but now my signal is at 100mV. Will noise become an issue at the 100mV range? Will a simple capacitor filter out enough noise for me to reliably measure current?
I am interested in noise for analog circuits specifically. I realize that in digital circuits, there are many noise generators due to switching. If I have a 100mV signal in a purely analog board in an aluminum box, is there typically enough noise to make the measurement unreliable (let's say +/- 15%). Are any filtering techniques required, and if so, what are some options?
What if that same signal was 0-100 uV?