Connecting a series resistor to adc

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seyyah

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I wonder how may a resistor connected series with an adc affect the measuring performance? Does it help to improve accuracy or reducing noise? Or what effects can it have?
 

It will produce a voltage divide effect with the ADC input resistance and capacitance. You can compensate with an increase of the gain of the stages preceding it.

Why would you put resistors in this position, or are you concerned about MUX stages?
 

Industrial practice is to connect (max 100)10 ohm resistor in series with A/D input and zener diod (0-Vmax) or transient voltage supressor for +/- inputs as protection.
As the input impedance of A/D input is usually more than 100k this will have marginal effect on the result of A-to-D conversion.
Are you happy with 0.01%?
 

Usualy ADCs (Inside of microcontroller) include sample and hold circuits.

Hold capacitor must charge in the sort time (data aqusition windows). System wrong convert voltage If you add serial resistor to ADC input.
 

Some ADCs throw nasty glitches out the input pin. A small value series resistor can help prevent those glitches from jolting the opamp that you're using to feed the ADC. Don't make the resistor too big, however, or you will have the problem that bunalmis described.
 

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