Lika SMRA User manual

User's guide
SMRA + MRA
Bearingless absolute encoder
Smart encoders & actuators

This publication was produced by Lika Electronic s.r.l. 2015. All rights reserved. Tutti i diritti riservati. Alle Rechte vorbehalten. Todos los
derechos reservados. Tous droits r serv s.
This document and information contained herein are the property of Lika Electronic s.r.l. and shall not be reproduced in whole or in
part without prior written approval of Lika Electronic s.r.l. Translation, reproduction and total or partial modification (photostat copies,
film and microfilm included and any other means) are forbidden without written authorisation of Lika Electronic s.r.l.
The information herein is subject to change without notice and should not be construed as a commitment by Lika Electronic s.r.l. Lika
Electronic s.r.l. reserves the right to make all modifications at any moments and without forewarning.
This manual is periodically reviewed and revised. As required we suggest checking if a new or updated edition of this document is
available at Lika Electronic s.r.l.'s website. Lika Electronic s.r.l. assumes no responsibility for any errors or omissions in this document.
Critical evaluation of this manual by the user is welcomed. Your comments assist us in preparation of future documentation, in order
to make it as clear and complete as possible. Please send an e-mail to the following address [email protected] for submitting your
comments, suggestions and criticisms.

General contents
User's guide...............................................................................................................................................................................................1
General contents....................................................................................................................................................................................3
Subject Index............................................................................................................................................................................................5
Typographic and iconographic conventions...............................................................................................................................6
Preliminary information......................................................................................................................................................................7
1 - Safety summary..........................................................................................................................................................................8
Safety.......................................................................................................................................................................................................................8
Electrical safety...................................................................................................................................................................................................8
Mechanical safety..............................................................................................................................................................................................9
2 - Identification.............................................................................................................................................................................10
3 - Mounting instructions...........................................................................................................................................................11
3.1 Overall dimensions..................................................................................................................................................................................11
3.2 Magnetic ring............................................................................................................................................................................................11
3.3 Installing the system..............................................................................................................................................................................12
3.3.1 Mounting the magnetic ring.................................................................................................................................12
3.3.2 Mounting the sensor.................................................................................................................................................12
3.3.3 Optional mounting tool...........................................................................................................................................14
4 – Electrical connections............................................................................................................................................................15
4.1 M8 cable specifications.........................................................................................................................................................................15
4.2 M12 8-pin connector.............................................................................................................................................................................15
4.3 Connection of the shield......................................................................................................................................................................16
4.4 Ground connection.................................................................................................................................................................................16
4.5 Zero setting/Preset input.....................................................................................................................................................................16
4.6 Counting direction input......................................................................................................................................................................16
5 - SSI interface...............................................................................................................................................................................18
5.1 SSI (Synchronous Serial Interface)...................................................................................................................................................18
5.2 MSB left aligned protocol....................................................................................................................................................................19
5.3 Recommended transmission rates...................................................................................................................................................20
5.4 Error bit........................................................................................................................................................................................................20
5.5 Helpful information................................................................................................................................................................................21
5.6 Recommended SSI circuit....................................................................................................................................................................21
6 - BiSS C-mode interface...........................................................................................................................................................22
6.1 Communication........................................................................................................................................................................................22
6.2 Single Cycle Data SCD...........................................................................................................................................................................23
6.2.1 SCD structure................................................................................................................................................................23
Position...........................................................................................................................................................................23
Error (nE)........................................................................................................................................................................24
Warning (nW)...............................................................................................................................................................24
CRC...................................................................................................................................................................................25
6.3 Control Data CD.......................................................................................................................................................................................25
Register address..........................................................................................................................................................25
RW....................................................................................................................................................................................25
DATA................................................................................................................................................................................26
CRC...................................................................................................................................................................................26
6.4 Implemented registers...........................................................................................................................................................................27
Preset...............................................................................................................................................................................27
Preset setting enable................................................................................................................................................29
Serial number...............................................................................................................................................................29
Command......................................................................................................................................................................30

Save parameters......................................................................................................................................................30
Save parameters and activate Preset.............................................................................................................30
Device ID........................................................................................................................................................................30
Time-out.........................................................................................................................................................................30
Software version.........................................................................................................................................................31
Manufacturer ID.........................................................................................................................................................31
6.5 Application notes.....................................................................................................................................................................................31
6.6 Recommended BiSS input circuit.....................................................................................................................................................32
7 - Diagnostic LED...........................................................................................................................................................................33
8 - Error and fault diagnostics..................................................................................................................................................34
9 - Maintenance..............................................................................................................................................................................35
10 - Troubleshooting.....................................................................................................................................................................36
11 - Default parameters list.......................................................................................................................................................37

Subject Index
C
Command............................................................................30
CRC............................................................................25 e seg.
D
DATA......................................................................................26
Device ID..............................................................................30
Error (nE)..............................................................................24
M
Manufacturer ID...............................................................31
P
Position.................................................................................23
Preset.....................................................................................27
Preset setting enable......................................................29
R
Register address................................................................25
RW..........................................................................................25
S
Save parameters...............................................................30
Save parameters and activate Preset......................30
Serial number....................................................................29
Software version..............................................................31
T
Time-out..............................................................................30
W
Warning (nW)....................................................................24

Typographic and iconographic conventions
In this guide, to make it easier to understand and read the text the following typographic and
iconographic conventions are used:
•parameters and objects both of Lika device and interface are coloured in ORANG ;
•alarms are coloured in R D;
•states are coloured in FUCSIA.
When scrolling through the text some icons can be found on the side of the page: they are expressly
designed to highlight the parts of the text which are of great interest and significance for the user.
Sometimes they are used to warn against dangers or potential sources of danger arising from the use of
the device. You are advised to follow strictly the instructions given in this guide in order to guarantee
the safety of the user and ensure the performance of the device. In this guide the following symbols are
used:
This icon, followed by the word WARNING, is meant to highlight the parts of the
text where information of great significance for the user can be found: user must
pay the greatest attention to them! Instructions must be followed strictly in order
to guarantee the safety of the user and a correct use of the device. Failure to heed
a warning or comply with instructions could lead to personal injury and/or damage
to the unit or other equipment.
This icon, followed by the word NOT , is meant to highlight the parts of the text
where important notes needful for a correct and reliable use of the device can be
found. User must pay attention to them! Failure to comply with instructions could
cause the equipment to be set wrongly: hence a faulty and improper working of
the device could be the consequence.
This icon is meant to highlight the parts of the text where suggestions useful for
making it easier to set the device and optimize performance and reliability can be
found. Sometimes this symbol is followed by the word XAMPL when instructions
for setting parameters are accompanied by examples to clarify the explanation.

Preliminary information
This guide is designed to provide the most complete and exhaustive information the operator needs to
correctly and safely install and operate the SMRA series bearingless absolute encoder. SMRA is
designed to measure rotary and linear displacements in industrial machines and automation systems. The
measurement system includes a magnetic ring and a magnetic sensor with conversion electronics. The
ring is magnetized with a coded sequence of North-South poles generating an absolute pattern. As the
ring turns without contact, the sensor detects the rotation and yields the absolute position information
through the SSI interface (order code SMRA-BG-... and SMRA-GG-...) or the BiSS C-mode interface (order
code SMRA-I7-...).
It is mandatory to pair the sensor with the MRA type magnetic ring.
To make it easier to read and understand the text, this guide can be divided into three main sections.
In the first section some general information concerning the safety, the mechanical installation and the
electrical connection as well as tips for setting up and running properly and efficiently the unit are
provided.
In the second section, entitled SSI interface, both general and specific information is given on the SSI
interface.
In the third section, entitled BiSS C-mode interface, both general and specific information is given on
the BiSS C-mode interface. In this section the parameters implemented in the unit are fully described.

SMRA - SSI and BiSS
1 - Safety summary
Safety
•Always adhere to the professional safety and accident prevention
regulations applicable to your country during device installation and
operation;
•installation and maintenance operations have to be carried out by
qualified personnel only, with power supply disconnected and stationary
mechanical parts;
•device must be used only for the purpose appropriate to its design: use for
purposes other than those for which it has been designed could result in
serious personal and/or the environment damage;
•high current, voltage and moving mechanical parts can cause serious or
fatal injury;
•warning ! Do not use in explosive or flammable areas;
•failure to comply with these precautions or with specific warnings
elsewhere in this manual violates safety standards of design, manufacture,
and intended use of the equipment;
•Lika Electronic assumes no liability for the customer's failure to comply
with these requirements.
lectrical safety
•Turn OFF power supply before connecting the device;
•connect the unit according to the explanation in the section ”4 – Electrical
connections”;
•connect Zero Setting/Preset and Counting direction inputs to 0VDC, if not
used;
- to set the encoder to zero/preset, connect Zero setting/Preset input to
+VDC for 100 µs at least, then disconnect +VDC; normally voltage must
be at 0VDC; zero/preset setting must be performed after Counting
direction setting; we suggest performing the zero/preset setting when
the encoder is in stop;
- Counting direction: increasing count = connect to 0VDC; decreasing
count = connect to +VDC;
•in compliance with 2004/108/EC norm on electromagnetic
compatibility, following precautions must be taken:
- before handling and installing the equipment, discharge
electrical charge from your body and tools which may come in touch
with the device;
- power supply must be stabilized without noise; install EMC filters on
device power supply if needed;
- always use shielded cables (twisted pair cables whenever possible);
- avoid cables runs longer than necessary;
- avoid running the signal cable near high voltage power cables;
- mount the device as far as possible from any capacitive or inductive
noise source; shield the device from noise source if needed;
- to guarantee a correct working of the device, avoid using strong magnets
on or near by the unit;
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- minimize noise by connecting the shield and/or the connector housing
and/or the sensor to ground. Make sure that ground is not affected by
noise. The connection point to ground can be situated both on the device
side and on user’s side. The best solution to minimize the interference
must be carried out by the user;
•do not stretch the cable; do not pull or carry by cable; do not use the cable
as a handle.
Mechanical safety
•Install the device following strictly the information in the section “3 -
Mounting instructions”;
•mechanical installation has to be carried out with stationary mechanical
parts;
•do not disassemble the unit;
•do not tool the unit;
•delicate electronic equipment: handle with care; do not subject the device
to knocks or shocks;
•protect the unit against acid solutions or chemicals that may damage it;
•respect the environmental characteristics of the product;
•we suggest installing the unit providing protection means against waste,
especially swarf as turnings, chips, or filings; should this not be possible,
please make sure that adequate cleaning measures (as for instance
brushes, scrapers, jets of compressed air, etc.) are in place in order to
prevent the sensor and the magnetic ring from jamming.
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SMRA - SSI and BiSS
2 - Identification
Device can be identified through the order code and the serial number printed
on the label applied to its body. Information is listed in the delivery document
too. Please always quote the order code and the serial number when reaching
Lika Electronic for purchasing spare parts or needing assistance. For any
information on the technical characteristics of the product refer to the
technical datasheet.
Warning: devices having order code ending with "/Sxxx" may have
mechanical and electrical characteristics different from standard and
be supplied with additional documentation for special connections
(Technical Info).
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3 - Mounting instructions
WARNING
Installation has to be carried out by qualified personnel only, with power supply
disconnected and mechanical parts compulsorily in stop.
WARNING
Install the unit providing protection means against waste, especially swarf as
turnings, chips or filings; should this not be possible, please make sure that
adequate cleaning measures (as for instance brushes, scrapers, jets of
compressed air, etc.) are in place in order to prevent the sensor and the
magnetic ring from jamming.
Make sure the mechanical installation meets the system's requirements for both
the sensor and the ring indicated in this guide.
3.1 Overall dimensions
Figure 1
3.2 Magnetic ring
It is mandatory to pair the sensor with the MRA type magnetic ring.
The Figure 1 shows how the sensor and the magnetic ring must be installed; the
arrow indicates the standard counting direction (increasing count when the
ring turns in the direction indicated by the arrow). See also the section “4.6
Counting direction input” on page 16.
WARNING
The system cannot operate if mounted otherwise than illustrated in Figure 1.
Please mind the direction of the cable outlet.
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SMRA - SSI and BiSS
3.3 Installing the system
Figure 2
3.3.1 Mounting the magnetic ring
1. Mount the magnetic ring 2 on the motor shaft;
2. mount the locking ring 3 and fasten the whole assembly to the motor
shaft by using six bolts type M3 x 20 UNI7688. Tighten the bolts
following the sequence indicated in the Figure. Recommended
tightening torque: 1.1 Nm.
3.3.2 Mounting the sensor
1. Fix the sensor 1 using two cylinder head bolts M4 x 25 UNI5931.
Recommended tightening torque: 2.5 Nm. Recommended minimum
bend radius of the cable: R  42 mm.
The max. allowed gap between the sensor and the magnetic ring is 1 ±0.2
mm (0.04” ±0.008”).
WARNING
Please be sure that the mounting tolerances indicated in Figure 3 are always
met. Avoid contact between the parts.
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SMRA - SSI and BiSS
Figure 3
WARNING
Mount the sensor as shown in the Figures. Please mind the direction of the
cable outlet. The system cannot operate if mounted otherwise than illustrated in
the Figures.
WARNING
The arrow in Figure 1 is intended to indicate the standard counting direction
(count up information when the ring turns in the direction of the arrow). See
also the section “4.6 Counting direction input” on page 16.
WARNING
After having installed the sensor on the magnetic ring a zero/preset setting
operation is compulsorily required. The zero/preset setting operation is further
required every time either the sensor or the ring are replaced. For any
information on the zero/preset setting operation please refer to the section “4.5
Zero setting/Preset input” on page 16 and (BiSS interface only) to the Preset
registers on page 27.
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SMRA - SSI and BiSS
3.3.3 Optional mounting tool
To ease the installation of the sensor we suggest using the optional mounting
tool. The order code is: TOOL LKM-2386 (for rings Ø 130 mm).
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SMRA - SSI and BiSS
4 – lectrical connections
WARNING
Electrical connection has to be carried out by qualified personnel only, with
power supply disconnected and mechanical parts compulsorily in stop.
WARNING
If wires of unused signals come in contact, irreparable damage could be caused
to the device. Please insulate them singularly.
Function M8 cable M12 8-pin
0VDC power supply Black 1
+VDC power supply * Red 2
Clock IN + / MA + Yellow 3
Clock IN - / MA - Blue 4
Data OUT + / SLO + Green 5
Data OUT - / SLO - Orange 6
Zero setting/Preset White 7
Counting direction Grey 8
* See the order code for power supply voltage level
XAMPL
SMRA-GG-1-08 +VDC = +5VDC ± 5%
SMRA-GG-2-08 +VDC = +10VDC +30VDC
4.1 M8 cable specifications
Model : LIKA HI-FLEX M8 cable
Wires : 6 x 0.14 mm2 + 2 x 0.22 mm2 (26/24 AWG)
Shield : tinned copper braid
External diameter : Ø 5.3 mm ÷ 5.6 mm
Conductor resistance : < 148 /km (0.14 mm2), < 90 /km (0.22 mm2)
Minimum bend radius : Ø x 7.5
4.2 M12 8-pin connector
Male, frontal side
A coding
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4.3 Connection of the shield
For signals transmission always use shielded cables. The cable shielding must be
connected properly to the metal ring nut of the connector in order to ensure a
good earthing through the frame of the device.
4.4 Ground connection
Minimize noise by connecting the shield and/or the connector housing and/or
the sensor to ground. Make sure that ground is not affected by noise. The
connection point to ground can be situated both on the device side and on
user’s side. The best solution to minimize the interference must be carried out by
the user.
4.5 Zero setting/Preset input
The output position information at a point in the shaft rotation can be set
either to 0 (SSI interface) or to a desired value called preset (BiSS C interface;
the preset value has to be set next to the registers Preset, see on page 27). The
Zero setting/Preset input allows the operator to activate the zero/preset value
through an input signal sent by a PLC or other controller. This can be very useful
for setting the zero position of both the sensor and the machine. To activate the
zero setting/preset function, connect the Zero setting/Preset input to +VDC for
100 µs at least, then disconnect +VDC; normally voltage must be at 0VDC; Zero
setting/Preset must be set after Counting direction. We suggest setting the
zero/preset when the encoder is in stop. If not used, connect the Zero
setting/Preset input to 0VDC.
NOT
In the BiSS interface the preset can be activated also by using the Save
parameters and activate Preset function of the Command register. For
detailed information please refer to the Preset registers on page 27 and the
Command register on page 30.
4.6 Counting direction input
It is also referred to as Complementary input.
The standard counting direction is to be intended with ring turning as
indicated by the arrow in Figure 1. The counting direction circuit allows to
reverse the counting direction. In other words it allows the count up when the
ring turns in reverse of the standard direction, i.e. in the opposite direction to
the one shown by the arrow in Figure 1. Connect the Counting direction input
to 0VDC if not used. Connect the counting direction input to 0VDC to have an
increasing count when the ring turns as indicated by the arrow in Figure 1;
connect the counting direction input to +VDC to have an increasing count
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when the ring turns in reverse of the standard direction, i.e. in the opposite
direction to the one shown by the arrow in Figure 1.
WARNING
After having set the new counting direction it is necessary to set the sensor to
zero/preset.
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SMRA - SSI and BiSS
5 - SSI interface
Order codes: SMRA-BG-…
SMRA-GG-…
5.1 SSI (Synchronous Serial Interface)
SSI (the acronym for Synchronous Serial
Interface) is a synchronous point-to-point serial
interface engineered for unidirectional data
transmission between one Master and one Slave.
Developed in the first eighties, it is based on the RS-
422 serial standard. Its most peculiar feature is that data transmission is
achieved by synchronizing both the Master and the Slave devices to a common
clock signal generated by the controller; in this way the output information is
clocked out at each controller's request. Furthermore only two pairs of twisted
wires are used for data and clock signals, thus a six-wire cable is required.
The main advantages in comparison with parallel or asynchronous data
transmissions are:
•less conductors are required for transmission;
•less electronic components;
•possibility of insulting the circuits galvanically by means of
optocouplers;
•high data transmission frequency;
•hardware interface independent from the resolution of the absolute
encoder.
Furthermore the differential transmission increases the noise immunity and
decreases the noise emissions. It allows multiplexing from several encoders, thus
process controls are more reliable with simplified line design and easier data
management.
Data transmission is carried out as follows.
At the first falling edge of the clock signal (1, the logic level changes from high
to low) the absolute position value is stored while at the following rising edge
(2) the transmission of data information begins starting from the MSB.
At each change of the clock signal and at each subsequent rising edge (2) one
bit is clocked out at a time, up to LSB, so completing the data word
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SMRA - SSI and BiSS
transmission. The cycle ends at the last rising edge of the clock signal (3). This
means that up to n + 1 rising edges of the clock signals are required for each
data word transmission (where n is the bit resolution); for instance, a 13-bit
encoder needs 14 clock edges. If the number of clocks is greater than the
number of bits of the data word, then the system will send a zero (low logic
level signal) at each additional clock, zeros will either lead (LSB ALIGNED
protocol) or follow (MSB ALIGNED protocol) or lead and/or follow (TREE FORMAT
protocol) the data word. After the period Tm monoflop time, having a typical
duration of 16 µsec, calculated from the end of the clock signal transmission,
the encoder is then ready for the next transmission and therefore the data
signal is switched high.
The clock signal has a typical logic level of 5V, the same as the output signal
which has customarily a logic level of 5V in compliance with RS-422 standard.
The output code can be either Binary or Gray (see the order code).
5.2 MSB left aligned protocol
“MSB left aligned” protocol allows to left align the bits, beginning from MSB
(most significant bit) to LSB (least significant bit); LSB is then sent at the last
clock cycle. If the number of clock signals is higher than the data bits, then
unused bits are forced to logic level low (0) and follow the data word. This
protocol can be used in sensors having any resolution.
The word has a variable length according to resolution, as shown in the
following table.
Sensor model Ring model Length of
the word
Max. number of
information
SMRA-BG-x-06-...
SMRA-GG-x-06-... MRA/130-64 13 bits 12 bits (4096 info/rev.)
SMRA-BG-x-07-...
SMRA-GG-x-07-... MRA/130-64 14 bits 13 bits (8192 info/rev.)
SMRA-BG-x-08-...
SMRA-GG-x-08-... MRA/130-64 15 bits 14 bits (16384 info/rev.)
The number of information per revolution results from:
2 to the power of resolution * number of ring poles
XAMPL
SMRA-GG-2-08-...: resolution = 08;
MRA/130-64: number of poles = 64.
Hence: 28 * 64 = 256 * 64 = 16,384 information per revolution
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The output code of the sensor can be GRAY or BINARY (see the order code).
Structure of the transmitted position value:
SMRA-xx-x-06-... bit 13 … 2 1
SMRA-xx-x-07-... bit 14 … 2 1
SMRA-xx-x-08-... bit 15 … 2 1
value MSB … LSB Error bit
5.3 Recommended transmission rates
The SSI interface has a frequency of data transmission ranging between 100 kHz
and 2 MHz.
The CLOCK signals and the DATA signals comply with the “EIA standard RS-422”.
The clock frequency (baud rate) depends on the length of the cable and must
comply with the technical information reported in the following table:
Cable length Baud rate
< 60 m < 400 kHz
< 100 m < 300 kHz
< 200 m < 200 kHz
< 400 m < 100 kHz
The time interval between two Clock sequence transmissions must be at least 16
µs ( Tp = pause time > 16 µs).
5.4 rror bit
The error bit is intended to communicate the normal or fault status of the Slave.
“1”: correct status (the sensor is working properly, there are no active
errors)
“0”: an error is active:
•position calculation error, invalid position value; the sensing
electronics is not able to read the ring; this problem may be
caused, for instance, by an excessive distance between the
sensor and the ring, by a wrong/reversed assembly of the
elements, by a damage to the magnetic surface of the ring;see
the section “3.3.2 Mounting the sensor“ on page 12;
•the power supply is not as required, please refer to the order
code;
•EEPROM error.
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