Ulvac UTM1600 Series, Instruction Manual

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6.8 Communication Specifications
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b. Multi-drop function ON
Fig. 6-7 Example of RS-485 Cable Wiring Connections (Multi-drop function ON)
(2) Cables used
RS-485 is a differential transmission and use twisted-pair cables in combinations as shown
in Fig. 6-7. The shield of the cable should be connected to case.
(3) Connecting the terminator
A terminator (120 Ω, 1/4 W min.) is required for connection.
Terminators are not necessary for multidropped turbo molecular pump with another pump
or pump to which the computer connects is connected to both ends (pump 1 through N-1
in Fig. 6-7).
However, connection of the terminator may prevent communications with certain cable
lengths and RS-485 device types. Connect the terminator to determine whether it is
required.
(4) Cable length
Connection cables can be extended up to 1.2 kilometers, but may be subjects to errors
depending on actual operational environment.