Field Bus

Since the beginning of the 90's bus systems are increasingly used, in particular open field bus systems
such as Profibus, Interbus and CANbus. Unlike conventional techniques these systems are economically
interesting. Field busses are not only economically favorable they also represent a new technology which
opens another dimension for the planning of system concepts incorporating dezentralized solutions. Field
busses enable the specific communication of automation components - bus nodes - among themselves. More Info Price

Measuring Systems

The principle of the incremental measuring system is the
scanning of a line pattern on a glass or plastic disc (see
Image 1). The states of the line pattern transparent or not
transparent are converted into electronic pulses by an
opto-electronic unit (e.g. transparent = 5V, not transparent
= 0V). The analysis of the signals is performed in an
evaluation unit by counting up or down with each pulse
The current count is stored in digital form and is instantly
available for evaluation More Info Price

Parallel Interface

All bits of a position are transferred simultaneously using
one line for each bit. Data transmission is done by two
transistors in push pull circuit. For example the signals
can be evaluated via digital entries of an PLC. The
conversion from gray to binary code has to take place iN
the control system, since the code of this method is
transmitted directly
The bit parallel interface is a very fast and for low resolutions cheap possibility of data transmission. For
high resolutions or machines of bigger size installation costs can rise rapidly so that other methods of data

transmission are more favourabT

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SSI Interface

For machines where several axis have to be automated (e.g. robots), the cabling of rotary encoders with bit-parallel
interface can become a problem, especially when high resolutions are necessary. A solution for this problem is
the synchronous-serial-interface (RS 422). The synchronous-serial-interface (SSI) enables a dat
transmission with only one 6 wire cable. Drivers that meet the RS 485 standard allow transmission rates up to 10
Mbps/s and line lengths up to 1200 m. This is entirely sufficient for most applications. The maximum transmission rate is dependant on the transmission length. Image 1 shows this relationship. More Info Price

Structure of an Absolute Encoder

The measuring system consists of a light source, a code
disc pivoted in a precision ball bearing and an opto-
electronic scanning device (see Image 1). A LED is used
as a light source which shines through the code disc and
onto the screen behind. The tracks on the code disk are
evaluated by an opto-array behind the reticle. With every
position another combination of slashes in the reticle is
covered by the dark spots on the code disk and the light
beam on the photo transistor is interrupted. That way the
signals.Fluctuations in the intensity of the light source are
measured by an additional photo transistor and another electronic circuit compensates for these. After the electronic signals are amplified and converted they are then available for evaluation.

code on the disc is transformed into electronic

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