Measurement-computing PC104-CTR10HD Manuel d'utilisateur télécharger pdf (Page 14)

5.0 ELECTRONICS AND INTERFACING

5.1 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 (Figure 4-1).

Figure 4-1. Voltage Divider

The object in using a voltage divider is to choose two resistors with the proper

proportions relative to the full scale of the digital input and the maximum signal

voltage.

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Measurement-computing PC104-CTR10HD Manuel d'utilisateur Page 14