SSI (S) Module (RMC150)

Important!
The SSI module requires RS-422 (5V differential) SSI inputs. It does not support single-ended SSI inputs or higher voltage inputs.

The SSI module for the RMC150 interfaces to feedback devices using the Synchronous Serial Interface (SSI) standard. Many types of transducers are available with SSI, including magnetostrictive displacement transducers (MDTs), absolute encoders, and laser measuring devices. SSI has a number of advantages over other transducer interfaces. First, it offers higher noise immunity. Second, it gives absolute positions. Third, it supports a wide variety of transducers. Finally, many SSI devices offer higher precision; for example, MDTs with SSI output are available with resolutions to 0.5µm.

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:

The following advanced parameters can be optionally set for axes with SSI feedback:

Specifications

For general specifications on the RMC150, see the RMC150 Overview topic.

General
Weight	74 g + 16 g (stock connectors)
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
Count Data Length	8 to 31 bits
Control Outputs
Range	±10 V @ 5 mA (2 kΩ or greater load) (For current output, use the VC2124 accessory:±10 mA to ±200 mA in 10 mA steps)
Tolerance	At 10 V: +200 mV, -100 mV At 0 V: ±50 mV At -10 V: +100 mV, -200 mV
Resolution	12 bits
Output Isolation	500 VAC, optically isolated
Overload Protection	One-second short-circuit duration
Overvoltage Protection	Outputs are protected by clamp diodes

LEDS

Axis 0 LED

Axis LED applies to the Drive 0 output or feedback input 0 as described below:

If Drive 0 is assigned to an axis that has an input (i.e. isn't output-only), then that axis will own the Axis 0 LED.
Otherwise, if a reference input axis (no output) uses input 0, then that axis will own the Axis 0 LED.
Otherwise, if Drive 0 is assigned to an output-only axis, then that axis will own Axis 0 LED.

Axis 1 LED

Axis 1 LED applies to the Drive 1 output or feedback input 1 as described below:

If Drive 1 is assigned to an axis that has an input (i.e. isn't output-only), then that axis will own the Axis 1 LED.
Otherwise, if a reference input axis (no output) uses input 1, then that axis will own the Axis 1 LED.
Otherwise, if Drive 1 is assigned to an output-only axis, then that axis will own the Axis 1 LED.

LED Colors

State	Description
Steady Off	No power or the output/input is not assigned to an axis.
Steady Green	The axis is either in closed loop control or is a reference axis. The axis is not halted.
Flashing Green	The output is in open loop and the axis is not halted (not possible for reference axes).
Flashing Red	A Closed Loop Halt or External Halt has occurred because an error bit is set (not possible for reference axes). The LED will not turn red due to a halt caused by a halt command.
Steady Red	An Open Loop Halt or Direct Output Halt has occurred because an error bit is set (for reference axes, any halt has occurred). The LED will not turn red due to a halt caused by a halt command.