Measurement Computing CIO-INT-32 - Manual (Page 17)

Install and solder the SIP in place. Install the SIP with the common pin (dot) in either
the HI or LO hole, then solder the SIP in place.
A resistor value of 10k (10000 ohms) is recommended. Use other values only if you
have calculated the necessity of doing so.
5.2 VOLTAGE DIVIDERS
If you wish to measure a signal which varies over a range greater than the input range
of a digital input, a voltage divider can drop the voltage of the input signal to the level
the digital input can measure.
A voltage divider takes advantage of Ohm's law, which states,
Voltage = Current * Resistance
and Kirkoff's voltage law which states,
The sum of the voltage drops around a circuit will be equal to the voltage
drop for the entire circuit.
Implied in the above is that any variation in the voltage drop for the circuit as a whole
will have a proportional variation in all the voltage drops in the circuit.
A voltage divider takes advantage of the fact that the voltage across one of the
resistors in a circuit is proportional to the voltage across the total resistance in the
circuit.
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