noiseresistors
What type of resistor technology would be best suited for a voltage divider that must be in the 10+ megaohm range that can work at a voltage of 800V+ across one resistor and have low as possible noise (used as feedback network for high voltage regulator) with a low temperature coefficient?
What techniques would minimize 1/f noise on my high voltage measurement with these resistors?
I'd consider this part with an extra stage of LC output filtering: -
I'd also consider adding 10nF (or whatever suits your bandwidth) capacitors on the ratiometric sensor outputs to ground to further reduce noise. Given that the outputs are ratiometric I'd also strongly consider measuring ratiometrically i.e. use Vcc as the reference for your ADCs - this cuts out a bunch of errors.
If it "explodes" you're doing something horribly wrong. That part is basically an LM7805.
Perhaps put a 2A fast-blow fuse in series with the input to protect the wiring (and check the connections- perhaps you have them reversed).
If you're using it in a car, that's a different matter, there are transients on a car electrical system that need to be protected against. A small wirewound series resistor (eg. 1 ohm 5W) and a hefty 14V TVS (eg. 3000W) would help with that.
And don't forget a capacitor on the input, and preferably one on the output (something like 47uF/25V would do for both).
simulate this circuit – Schematic created using CircuitLab
Best Answer
Metal film resistors work best for lower 1/f noise. 1/f noise arises through the interaction of the carriers with grain boundaries in the bulk material. A metal film is less likely to have distinct carrier disruptions at crystal boundaries (depending upon the allotype). However, metal film resistors can have inductance, depending upon how they are made and this may not work for you. Keep in mind that a 10 MOhm resistor may have significant Johnston noise.