Advantech PCI-1724U Manual do Utilizador descarregar pdf (Página 35)

27 Chapter 3

3.3.5 Current Mode (Sink type):

Caution: The external voltage should be under 30 V.

Ri: Internal resistor= 499 ohm

Vext: External voltage

Isink : The controlled current output (0~20 mA)

Since Isink =Vext / (Ri+RL), RL can not be higher than | Vext/Imax | -Ri

For Example: Vext=24 V, Imax=20 mA

RL max = | 24 V / 20 mA | - 499= 701 (ohm)

3.4 Field Wiring Considerations

When you use the PCI-1724U to acquire data from outside, noises in the

environment might significantly affect the accuracy of your measure-

ments if due cautions are not taken. The following measures will be help-

ful to reduce possible interference running signal wires between signal

sources and the PCI-1724U.

The signal cables must be kept away from strong electromagnetic sources

such as power lines, large electric motors, circuit breakers or welding

machines, since they may cause strong electromagnetic interference.

Keep the analog signal cables away from any video monitor, since it can

significantly affect a data acquisition system.

D/A n

Data Bus

Load

Vext

Isink_n

AGND

n: 0~31

Internal External

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Advantech PCI-1724U Manual do Utilizador Página 35