Measurement-computing PC104-DIO48 Manuel d'utilisateur télécharger pdf (Page 19)

5.3 VOLTAGE DIVIDERS

If you wish to measure a signal which varies over a range greater than

the input range of a digital input, a proper voltage divider will drop the

voltage of the input signal to a safe level.

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.

In a voltage divider, the voltage across one of the resistors in a circuit is

proportional to the ratio of that resistor to the total resistance in the

circuit.

Therefore, you setup a voltage divider choosing two resistors with the

proper proportions relative to the full scale of the voltage input and the

maximum signal voltage to the board.

Figure 5-2. Voltage Divider

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Measurement-computing PC104-DIO48 Manuel d'utilisateur Page 19