LINEPULS & LINECOD catalogue 2016 in English

LINECOD
Additional functions for SSI and BiSS encoders
Using the Zero setting / Preset function, the output value can be set either to zero (reset)
or to a desired value (preset) via an external signal issued by a PLC or other controller device.
When the internal microprocessor receives the signal it resets or presets the output information.
This can be very useful, for example, for synchronizing the encoder readout with
the 0 mechanical position of the axis you need to measure. To set the zero (or the preset),
the Zero setting/Preset signal must be connected to +Vdc for 100 μs at least; then it must
be disconnected. In normal conditions its voltage must be at 0Vdc.
The Zero setting/Preset operation must be performed after having set the Counting direction.
We suggest setting the zero/Preset when the encoder is in stop.
Please note that a zero setting operation is compulsorily required after having installed the
sensor on the magnetic tape. The zero setting operation is further needed every time either
the sensor or the tape are replaced in an existing system.
Zero setting / Preset input
The counting direction circuit allows to reverse the counting direction. In other words it
allows the count up when the sensor moves in reverse of the standard direction.
The standard counting direction is to be intended with sensor moving as indicated by the
arrow in the upper face of the magnetic tape (provided that the sensing head is mounted
properly). Connect the counting direction input to 0Vdc to have an increasing count when
the sensor moves as indicated by the arrow in the tape; connect the counting direction input
to +Vdc to have an increasing count when the sensor moves in reverse of the standard
direction, i.e. in the opposite direction to the one shown by the arrow in the tape.
Connect the Counting direction input to 0Vdc if not used.
Counting direction input
In specific SSI models an error bit is provided at output. It is intended to communicate the
normal or fault status of the encoder.
“1”: correct status (no active error)
“0”: an error is active when the following conditions typically occur:
• reading error: the sensor is not able to read the tape correctly; among the possible
causes are: the tape is not installed properly (for instance: the tape is mounted
contrariwise to the sensor; or it is mounted upside down); the tape magnetic
surface is damaged somewhere; the sensor is not working properly;
• frequency error: the sensor is travelling too fast over the tape.
Refer to the specific encoder’s documentation for the position of the error bit in the frame
and its proper meaning.
Error bit
The parity bit is an optional function used for checking in a very basic way whether errors
occur during transmission. It is the simplest form of error detecting code and offers the
advantage that only one bit is required for error detection. On the other hand it only indicates
that a parity error occurred in the transmission and there is no way to determine which
particular bit is corrupted. Furthermore the parity bit is only guaranteed to detect an odd
number of bit errors. If an even number of bits have errors, the parity bit records the correct
number of ones, even though the data is corrupt. It can be either even or odd. Lika encoders
provide an ODD parity bit. Thus the sum of the bits having logic level 1 in the character has
to be odd.
Refer to the specific encoder’s documentation for the position of the parity bit in the frame.
Parity bit
41