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II - DCE FEL ČVUT v Praze

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SIMATIC S7 Ex Analog Modules<br />

3.5 Connecting Loads/Actuators to the Analog Output Module<br />

SM 332; AO 4 x 0/4...20 mA<br />

Introduction<br />

Lines for analog<br />

signals<br />

Isolated analog<br />

output modules<br />

Abbreviations<br />

3-36<br />

The analog output modules can be used to supply loads/actuators with<br />

current.<br />

Shielded lines twisted in pairs are used for analog signals . So as to reduce<br />

interference influence .<br />

You should ground the shield of the analog lines at both ends. If there are<br />

differences in the potential between the line ends , an equipotential bonding<br />

current can flow across the shield and cause interference in the analog signals.<br />

In this case, the shield should only be grounded at one end of the line.<br />

There is no metallic connection between each of the reference points M0- ...<br />

M3- of the analog circuits and the M terminal of the CPU in the isolated<br />

analog output modules.<br />

Isolated analog output modules are used when a difference in potential UISO<br />

can occur between the reference point of the analog circuit M0- ... M3- and the<br />

M-terminal of the CPU. Take particular care to ensure that the difference in<br />

potential UISO does not exceed the permissible value. In cases where it is<br />

possible that the permissible value is exceeded, provide a connection<br />

between the terminals M0- ... M3- and the M-terminal of the CPU.<br />

The abbreviations used in Fig. 3-13 have the following significance:<br />

QI0- ... QI3-: Analog outputs current<br />

M0- ... M3-: Reference potential of analog output circuit<br />

RL: Load/actuator<br />

L+: Power supply connection 24 V DC<br />

M : Ground terminal for 24 V DC power supply<br />

UISO: Difference in potential between reference points of channels<br />

M0- ... M3- or between the channels and M- terminal of the<br />

CPU.<br />

I/O Modules with Intrinsically-Safe Signals<br />

C79000-G7076-C152-04

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