The idea of the RC network is to slow the response time to below the noise
frequency. Since noise is generally higher in frequency than the signal
you're measuring you set up a low pass filter- i.e. RC network. Generally
the values aren't that critical. A larger RC time constant (bigger resistor
and / or capacitor) will have a lower frequency cut off. Unless you're
working with a high sampling rate (>10 times second, unlikely with a
pressure sensor) I wouldn't worry about the values. Just toss in a cap 0.1
to 0.47 and a resistor 500 to 1K and move on.

As to the best type of capacitor, probably polyester is best, ceramic
should be fine, I'd avoid an electrolytic.

-Denny


I have an mpu with ADC and a couple of pressure sensors connected to the
ADC through about 2" of wire.

I have found that using sheilded wire helps in noise reduction.

The sensor manufacture recommends an RC network on the output using a 750
ohm resistor and a .33uF cap, but doesn't specify what type components.

What type capacitor would be best, and a second best?

Would any type resistor work well. Would two resisitors in parallel work
better than one resistor or two in series to form 750 ohms (hard to find
locally), as far as not picking up noise?

It would be easier to put the rc network at the sensor. Would this work as
well as putting the rc network near the ADC?

Thanks for any help.

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