Advantech PCI-1720U Uživatelský manuál stáhnout pdf (Strana 32)

PCI-1720U User Manual 26

5.3 Current Sink Connections

The PCI-1720U's current loop output uses a 0 to +5 V (unipolar) voltage

output as each channel’s driving source. Current drive circuits consist of

a power field-effect transistor (FET). The current output’s voltage bias

must be less then 50 V for accurate results. The card also provides an

internal +12 V power source for current loop excitation.

You can use three types of current sink connections:

1. Grounded load with a floating power supply.

2. Floating load with a grounded power supply.

3. Floating load with an internal +12 V power supply.

These are shown in the following illustrations.

Figure 5.4: Grounded-load connection with a floating power supply

Figure 5.5: Floating-load connection with a grounded power supply

+ -

SINK

AGND

Internal Side

External Side

0 ~ 20 mA

4 ~ 20 mA

Grounded

Load

Internal Side External Side

SINK

AGND

0 ~ 20 mA

4 ~ 20 mA

Floating

Load

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Advantech PCI-1720U Uživatelský manuál Strana 32