User Manual

7 Hardware
transducers. Finally, many SSI devices offer higher precision; for example, MDTs with SSI
output are available with resolutions to 2µm.
Note: Linear MDTs with SSI output should be of the synchronized type. Non-synchronized is
not well-suited for motion control.
See the SSI Fundamentals
topic for details on the SSI standard.
Features
•
Two axes of SSI feedback per module
• Supports SSI devices with Binary or Gray Code data from 8 to 31 bits in length
• Differential RS-422 SSI interface
• Two isolated, ±10 V, 12-bit control outputs per module
• Current output up to ±200 mA with VC2124 converter option
Part Number
The part number of the SSI module is Sn, where n is the number of SSI modules.
For example, RMC150E-S1 is an RMC150E with one SSI module. RMC150E-S3-Q1 is an
RMC150E with three SSI modules and one Quadrature module.
Setting Up the SSI Module
To set up axes with SSI feedback, read the following topics:
SSI Wiring
SSI Scaling
The following parameters must be also set for axes with SSI feedback:
• SSI Data Bits
• SSI Format
The following advanced parameters can be optionally set for axes with SSI feedback:
• SSI Clock Rate
• Wire Break Detection
• SSI Overflow Mode
• SSI Home Source
Specifications
For general specifications on the RMC150, see the RMC150 Overview topic.
SSI Interface
Inputs
Two RS-422 differential (does not support single-ended)
Clock Outputs
Two RS-422 differential (does not support single-ended)
Clock Frequency
user-selectable 230 kHz, 921 kHz
Input Impedance
Data + Input: 140 Ω
Data - Input: 150 Ω
Required Cable Type
Twisted pair, shielded
Maximum Cable Length
Transducer Dependent, approx. 300-600 ft. See the SSI Clock Rate
topic for details.
ESD Protection
15 kV
Resolution
Transducer dependent
Count Encoding
Binary or Gray Code
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