A

Analog interface

Standard analog interface: As required from 4 to 20 mA, or 0 to 10 V output signal.

B

Baud rate

Gives the signal rate and hence the speed of serial data trans­fer in bits per second.

Bend radius

In cabling terms, the bend radius relates to the smallest curve radius a cable may have when installed, without the cable properties being altered. The bend radius is given in relation to the cable diameter.

Bus system

A system for transferring data between multiple devices over a common cable. A bus system makes it possible to control all sensors and actuators centrally. Additional information such as process data, service data and diagnostics data can also be exchanged.

Well known examples are:

DeviceNet, PROFIBUS, CANopen, PROFINET, EtherNet/IP, EtherCAT.

Additional information on bus systems can be found in this glossary under the CANopen, DeviceNet, EtherCAT, EtherNet/IP, PROFIBUS and PROFINET entries.

C

CANopen

CANopen: is a communication protocol based on CAN.

User organization: CiA (CAN in Automation)

More detailed information about this technology is available at www.can-cia.org

Channel

Signal path upon which a signal is output.

Code disc

--See “Output frequency, maximum“ on page 10Code type

Unique encoding of the measured values according to a defined scheme at the encoder output. In practice, different codes are used for different electrical interfaces, e.g. SSI interface with Gray code.

Cycle

--See “Service life“ on page 11

D

DeviceNet

DeviceNet is a CAN based communication protocol.

User organization: ODVA

More detailed information about this technology is available at www.odva.com

Differential evaluation

Evaluation of signals produced by a circuit which produces a sig­nal and its invert. The 1/0 level, or sine/cosine signals are trans­ferred in the form of voltage differences between two cables. In this way, the signal used (the difference) remains uncorrupted as interference normally affects both cables equally.

Drag chain use suitability

Drag chain use suitability is the ability of cabling to be used in moving applications. PUR cabling is suitable for drag chain use, but PVC cabling is of limited suitability or completely unsuitable.

In the case of PUR cabling, the number of bend cycles is gener­ally greater and the bend radius smaller than with PVC cabling.

Drum circumference

The resolution in mm of a wire draw encoder can be deter­mined using the circumference of the drum and the resolution of the rotary encoder (e.g. 12 bits per revolution).

E

EMC

Electromagnetic compatibility (EMC) means that technical equipment should not be affected by electromagnetic interfer­ence. This is achieved both by limiting sources of interference in devices and by devices being designed to be sufficiently resistant to interference. EMC is regulated by EU Directives and Standards.

Enclosure rating

The enclosure rating indicates the degree of protection of a machine or sensor against contact and penetration by impuri­ties and water. The enclosure ratings begin with the letters IP, followed by the first digit, which indicates the degree of protec­tion provided against touch and particles. The second digit describes the protection against penetration by water.

Encoders

Encoders are sensors for monitoring position, angle and speed. Essentially, encoders can be categorized as rotary or linear. Rotary encoders are sub-divided into incremental and absolute encoders. Linear encoders are further sub-divided into wire draw encoders and non-contact linear encoders.

Encoders, absolute

Absolute encoders generate information relating to position, angle and rotation counts in type-specific angle steps. For this, a unique code pattern is assigned to each angle step. The num­ber of code patterns available per revolution determines the resolution. Each code pattern forms a unique reference, and is therefore absolute position information. There is therefore no need for a reference run after switching on. A singleturn encoder measures the absolute position within a revolution. A multiturn encoder not only provides the position within a revolution but also the number of revolutions.

Encoders, incremental

Incremental encoders generate information related to position, angle and number of rotations. The number of lines per revolu­tion determines the number of impulses that the encoder trans­mits to the control unit for each revolution. The current position can be determined by the control unit counting these impulses from a reference point. When the machine is switched on, a reference run to the reference point is required to determine the actual position of the encoder.

Error limit

The error limit is the largest positive or negative deviation of any angle position (absolute) or of a measured angle (incre­mental) from the true value.

EtherCAT

EtherCAT is an Ethernet based fieldbus.

User organization: EtherCAT Technology Group

More detailed information about this technology is available at www.ethercat.org

EtherNet / IP

EtherNet / IP is an Ethernet based fieldbus.

User organization: ODVA

More detailed information about this technology is available at www.odva.com

F

Fieldbus

Bus system in the process area for direct connection of sensors and actuators that have their own intelligence. Data in digital form is transferred between sensors, actuators and control de­vices via a fieldbus. This transfer must be as rapid as possible, i.e. close to real time. For this, a fixed minimum and maximum response time must be guaranteed.

Flange

Part of the encoder for fixing to the customer installation inter­face. There are various mechanical versions, for example:

Gray code

Constant code that is also used with the SSI interface. When the position value changes from one value to the next, only one data bit changes. This ensures reliable data transfer.

Gray excess code

If a suitable section for encoder resolution is extracted from the middle of the complete Gray code, this results in the “Gray Ex­cess Code” (capped Gray code). The use of this Gray excess code allows only a single data bit to be altered even when the encoder crosses zero, although the number of steps is not 2 n where n is a whole number.

H

Halogen-free (wiring technique)

Cables and wiring are said to be halogen-free if the materials used do not contain salt forming chlorine, fluorine, bromine or iodine. The insulation and sheath materials of these cables consist of polymers based on pure hydrocarbons. When such materials are burned, no corrosive or toxic gases are produced, but only water vapor and carbon dioxide.

HIPERFACE® 

High Performance Interface (HIPERFACE®) is a hybrid interface developed by SICK that can transfer analog speed values and digital position values. Electrical compatibility is guaranteed by the use of HIPERFACE® as the obligatory interface for all physi­cal parameters.The advantages of HIPERFACE® are that only one interface is required on the drive electronics for all applications, only one type of signal cabling is needed between the drive electronics and the signal encoder and manual configuration of the speed sensor is not necessary.

HIPERFACE® DSL

The High Performance Interface DSL is a pure Digital Servo Link interface developed by SICK that provides new servo drive system architecture for HIPERFACE® with a completely new range of options as it is not hybrid (analog/digital), but is completely digital.

Thanks to the innovative and interference-free HIPERFACE DSL® protocol, rugged and reliable communication can be achieved using just two wires that are integrated into the motor cable. In addition, the digital protocol requires a minimum of connection

cables between the frequency inverter and the motor feedback system.

The absence of motor feedback connections achieves signifi­cant cost savings and distinctly increased performance.

HTL push-pull

High Voltage Transistor Logic functions with a voltage supply in the range 10 and 30 V DC, with 24 V DC being the most usual. “Low” is defined as an output of between 0 V and 3 V and “high” as between VCC and VCC - 3.5 V.

I

Interface, electrical

Connection point between two devices or systems. The devices or systems on either side of an interface are connected to each other by interface cabling over which data, addresses and control signals are exchanged. The term interface embraces the complete functional, electrical and constructive conditions that make up the point of contact between the devices or systems. Depending on the type of data transfer, a distinction must be made between parallel (e.g. Centronics, IEEE 488) and serial interfaces (e.g. RS-422, RS-423, RS-485) that are designed for differing transfer speeds and distances.

Interface, mechanical

--See “Flanges

Inverted signal

Reciprocal signal for the suppression of interference impulses when using differential sampling.

A¯A90° el.360° el.Measurement step

A = Original signal; Ā = Inverted signal.

--See “Differential evaluation“ on page 6

J

Jitter

From the English verb “to jitter”: flicker, tremble; time variation of the output signal resulting from constantly present tolerances.

L

Linear encoders

A linear encoder is for frictionless length measurement and de­termining positions. A read head samples a code pattern or the magnetic field of a magnetic scale and outputs the appropriate electric signal.

Principle of operation

Linearity

The accuracy of wire draw encoders is described by the linear­ity. This indicates the maximum deviation for the measurement of a defined measurement distance or rotation. In contrast to repeatability, this relates to the measuring range covered and not to the positioning point.

The data sheet values for wire draw encoders refer to the par­ticular measuring range.

M

Material resistance, PUR

Flexible silicone and halogen-free cabling with PUR outer sheath: The oil and fire resistance requirements of VDE 0472 are ful­filled. Can be used in drag chain applications with a minimum bend radius. This cabling is most suitable for flexible use in robot technology, for machine tools, as well as for machining produc­tion.

Material resistance, PVC

Pure PVC cables, suitable for medium mechanical strain in packaging machines as well as for assembly and production lines: good resistance to acids and alkalis and hence ideal for use in the foods and drinks industries. Resistance to wear as well as oil and chemical resistance is limited.

Measurement range

The range within which a rotary or linear encoder can produce a valid measurement signal.

Measurement step

There is a differentiation here between the measurement step for absolute and incremental measurement systems.

Incremental measurement systems:

In this case, the measurement step represents the period of the output signal. Here, the number of periods is the same as the number of lines per revolution on the measurement scale, or a multiple thereof.

Absolute measurement systems:

In this case the measurement step is the smallest possible angular movement of the rotor that will produce a change in the output signal.

Measurement step deviation

The measurement step deviation indicates the maximum measurement deviation from measurement step to measure­ment step. For this, measured values are taken at one or more adjacent positions in the test range and their maximum devia­tion from the desired value determined.

Multiturn (MT)

A version of an absolute encoder that in addition to the angular position of the shaft (singleturn) can also definitively determine and output the number of shaft rotations (multiturn).

Example: Magnetic multiturn with gearing.

N

NPN Open Collector

The NPN Open Collector is an interface based on an output circuit with an NPN transistor.

An open collector is the unconnected collector connection of an NPN transistor, whose emitter is connected to earth and whose collector is connected to the output.

NPN output

CEB

NPN output is an interface based on an output circuit with NPN transistor.

Offset

The difference between the actual physical value and the preset value is described as the offset. This can be both a position offset for position measurement, as well as a voltage offset.

Offset value2000Position:Preset value3000Actual value1000

Output frequency, maximum

The maximum encoder output signal frequency, for which the correct sequence of the code values is assured is called the maximum output frequency.

The formula used is as follows:

PNP output

ECB

The PNP output is an interface based on an output circuit with a PNP transistor.

Preset

For absolute encoders, a preset value can be allocated to the actual physical position value. In the case of an allocation via the set wire, this equates to the value 0. For programmable absolute encoders, the preset value can be any value within the measuring range.

PROFIBUS

PROFIBUS is a fieldbus for industrial communications.

User organization: PNO (PROFIBUS Nutzerorganisation e. V.)

More detailed information about this technology is available at www.profibus.com

PROFINET (Process Field Network)

PROFINET is an Ethernet based fieldbus.

User organization: PNO (PROFIBUS Nutzerorganisation e. V.)

More detailed information about this technology is available at www.profibus.com

R

Reference signal

--See “Zero pulse“ on page 13

Repetition accuracy

--See “Reproducibility“ on page 10

Reproducibility

Reproducibility, repetition accuracy or repeatability is defined as the maximum distribution from at least five consecutive measurements, carried out under identical conditions.

Resolution

The resolution is expressed as the number of impulses per revolution or path units.

If, for example a rotary incremental encoder has a resolution of 12 bits, this means the number of impulses is 4096.

The formula for calculation is: Number of impulses = 2X, where x is the resolution in bits.

Rotation direction, clockwise (cw)

Rotation to the right, when viewing the shaft.

Rotation direction, counterclockwise (ccw)

Rotation to the left, when viewing the shaft.

S

Sampling frequency

The frequency with which the signal periods of a sensor system are measured per second.

For incremental measuring systems, the speed is limited by the maximum sampling frequency.

Sampling, magnetical

Position, angle and speed determination for rotary or linear en­coders using permanent magnets and appropriate evaluation units to determine the magnetic field. Encoders with magnetic sampling are usually of lower resolution than optical ones.

_Permanent magnetHall sensor

Sampling, optical

Position, angle and speed determination for rotary or linear encoders using LEDs, code patterns and photo-diodes.

The line marks (for incremental encoders) or codes (for ab­solute encoders) are inscribed as digital patterns on a glass, metal or plastic disc and are sampled by a light source (light emitting diode) and photo-diodes.

Encoders with optical sampling are usually of higher resolution than magnetic ones.

1 LED; 2 Lens; 3 Reference point; 4 Code disc; 5 Mask; 6 Photo-diode.

Code discs: Left incremental, right absolute.

Scaling

For programmable encoders, the encoder actual value is multi­plied by a scaling factor. This means that the resolution can be adapted to the application in question.

Service life

For rotary encoders, the service life of the bearings represents the overall service life of the encoder expressed in revolutions.

For wire draw encoders, the service life is expressed as the total number of cycles. A cycle is defined as one withdrawal and rewind movement (load cycle).

The service life depends on the type of load. This is influenced by factors such as the environment, the installation location, the measuring range in use, the travel speed and acceleration. If the value of one or more of these influencing factors is in the high range, the service life may be reduced proportionally.

Shaft

The component of a rotary encoder that transfers the rotation movement and torque from the application to the sensor unit of the encoder.

Shaft coupling

A shaft coupling is for the indirect connection of two shafts to balance radial, axial or angular offset.

Shaft load capacity, axial

The axial shaft load capability describes the load capacity along the axis of the encoder shaft.

Shaft load capacity, radial

The radial shaft load capability describes the load capacity about the radius along the encoder shaft. For this, the point of action must be applied to the end of the shaft.

Shielding

The shielding of equipment or connecting cables is the design-dependent protection of equipment against radiated electro­magnetic interference. Sensitivity to radiated electromagnetic interference, as well as the intensity of radiated electromag­netic interference, must be reduced by full shielding so that the encoder can be used properly. This should be extensive and all around.

Silicone-free (connections)

Silicone-free connections must be used in certain industrial fields, such as paint shops. The reason for this is that silicones can reduce the effectiveness of or disrupt adhesive or other joints.

Sine-Cosine interfaces

Unlike conventional pulse signals, sine-cosine signals are emit­ted in sine-wave form. These signals can be output at a higher resolution, as there is also an option to sample the signals using an analog-digital converter. For this reason also, encod­ers with sine-cosine interfaces are preferred for demanding servo applications for which a high level of accuracy is required. In addition to the signals, a zero set can also be emitted, from which the absolute position can be calculated.

Singleturn (ST)

A version of an absolute encoder that can definitively determine and output the angle position within a single revolution.

SSI

A synchronous serial interface is a standardized interface originally developed by Max Stegman GmbH (now SICK) for serial data transfer that makes it possible to transmit absolute positions. The advantage of this type of transfer is that, as well as the time of the recording of the position, the speed of the data transfer can be controlled by the PLC. This guarantees safe transfer.

Starting torque

The torque required to move a shaft from the rest position in the rotation direction.

Stator coupling

The stator coupling compensates for both the radial and axial shaft movements of the drive element as well as installation tolerances without significantly affecting the accuracy of hollow shaft encoders. The stator coupling absorbs the torque derived from the bearing friction during angular acceleration.