Omega Engineering PCI-DIO96 user manual Voltage Dividers

The most convenient way to use solid state relays and a PCI-DIO96 board is to use a Solid State Relay Rack. An SSR Rack is a circuit board with input buffer amplifiers that are powerful enough to switch the SSRs. The buffer amplifiers and SSRs are socketed.

The standard buffer amplifiers are inverting types, meaning that a low input from a DIO 82C55 outputs a high to the SSR which turns it on (“closes” the SSR output). If desired, non-inverting amplifiers can be specified.

7.3 VOLTAGE DIVIDERS

If you wish to measure a signal that varies over a range greater than the input range of a digital input, use a voltage divider to drop the voltage of the input signal to the level the digital input can measure.

Ohm's law states:

Voltage = Current * Resistance

Thus, 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 voltage across the total resistance in the circuit (Figure 7-2).

When designing a voltage divider, choose two resistors with the proper proportions relative to the

Signal

High

R1

Signal

Volts Vin

R2

Signal

Low

V1

Board

Input

V2

Vout

Ground

full scale of the digital input and the maximum signal voltage.

The formula for voltage attenuation is:

SIMPLE VOLTAGE DIVIDER - Vin = R1+R2

Vout R2

Figure 7-2. Voltage Divider

	The variable Attenuation is the
Attenuation = R1+R2	proportional difference between the
R2	signal voltage max and the full scale of
	the analog input.
	For example, if the signal varies
2 = 10K+10K	between 0 and 10 volts, and you wish to
10K	measure that with a PCI-DIO96 board

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