Measurement-computing ADAC/5500 Series Manual de usuario descargar pdf (Pagina 21)

ADAC Series PCI Boards 795 - 16 - ADAC/5500 Series User Manual

4.1.2.2 Pseudo-Differential (PD)

For multiple signal sources that share a common ground (signals must be local to one another), the Pseudo-

Differential mode may be the most desirable. The Pseudo-Differential configuration is similar to Single-

Ended, but the analog low side of each signal is isolated from analog ground (AGND) by a 10 MΩ resistor and

a capacitor. All input returns are tied together to PDIN. Pseudo-Differential configuration allows the system to

reject any common-mode voltage difference that may exist.

Pseudo Differential configuration should be used when:

• Common Mode Voltage exists

• Common Mode Noise does not exist

• Each Source has a local ground

• Input signals are greater than 1 V (High Level)

• Signal leads are longer than 12 feet

Figure 4.2 shows proper wiring for Pseudo-Differential configuration.

Figure 4.2

Pseudo-Differential Configuration

4.1.2.3 Fully-Differential (DIFF)

In installations where each Ground Referenced Source signal has a local ground (signal located remote from

one another), the Fully-Differential configuration must be used. Since the Fully-Differential configuration

only responds to the difference in a signal between its high and low voltages, any Common Mode Voltage will

be cancelled out. In addition, Fully-Differential configuration provides the best performance of the three

configurations in an electrically noisy environment.

The Fully-Differential configuration should be used when any of the following exists:

• Each source has a local ground

• Signal sources are remote from one another

• Common Mode Voltage exists

• Common Mode Noise exists

• Signal sources are low-level (less than 1 V)

• Signal source leads are longer that 12 feet

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Measurement-computing ADAC/5500 Series Manual de usuario Pagina 21