LINEPULS & LINECOD catalogue 2016 in English

LINEPULS • LINECOD
Technical information
There are two types of magnetic tapes for incremental encoders: MTx tapes and MTSx tapes.
MT tapes are 10 mm wide while MTS tapes are 5 mm wide.
As in an incremental measuring system the tape has a systematic sequence of North and
South poles recurring indefinitely, there is virtually no limit to its measuring length (see on
page 14). Standard incremental tapes up to 100 m long can be supplied, they can be cut
to length accorwding to application requirements. You are required to indicate the desired
size under the option LENGTH in the order code.
Tape dimensions
The magnetic tapes for absolute encoders, MTAx type tapes, are 10 or 20 mm wide, according
to models.
An absolute tape encompasses a coded sequence of North-South poles generating a
pseudo-random absolute pattern, so there is a limit to the number of information it can
provide as well as to its overall length. The max. measuring length of the absolute encoders
is indicated in the datasheet under the section “Mechanical specifications”. Unless otherwise
indicated, any absolute tape section shorter than the max. measuring length can be supplied
on request.
When you need to order the tape please calculate its length as follows:
length of the travel to be measured + length of the sensing head + two safety sections at
both ends each one being min. 1-pole pitch long + additionally 1 cm at both ends if you
mount the optional tape terminals.
The magnetic sensors (MR magneto-resistive sensors or Hall sensors) are located inside the
readhead and designed to translate the information from the magnetic field generated by
the North-South poles of the tape into an electrical signal.
In an incremental encoder the magnetic sine waves are converted into two separate sinecosine
signals phase-shifted by 90 electrical degrees.
While in an absolute encoder the sequence of coded poles is converted into an absolute serial
signal. The signals are processed and optimized by the converting circuitry before being
output. The sensing elements are designed and arranged in order to minimize the effects of
the external static magnetic fields.
The converting circuitry (otherwise referred to as translation circuitry) is designed to collect
the signals from the magnetic sensor and convert them into standard output signals.
Signal conditioning processes allow to obtain signals that are optimized for the subsequent
controller and the different environmental conditions.
Using interpolation techniques further allows to interpolate the signals, that is to convert
the signals to a higher sampling rate (upsampling). In this way it is possible to provide enhanced
measuring resolutions to output.
The converter can provide the following output signals or information to the subsequent
controller:
• square wave signals phase-shifted by 90 electrical degrees;
• sine-cosine signals phase-shifted by 90 electrical degrees;
• absolute information via serial SSI and BiSS interfaces;
• absolute information via fieldbus interfaces;
• current and voltage analogue signals.
Magnetic sensors
Converting circuitry
12