Specifications

Positioning IP 240
10.13 Methods of Synchronization
Positioning is possible with the IP 240 only when the actual value has been synchronized. Three
methods of synchronization are available for this purpose:
• Reference point approach
A reference point approach synchronizes the actual value to a fixed point in the traversing
range.
• Software-controlled synchronization
The actual value is synchronized every time a control bit with a value of ”1” is transferred.
• Synchronization with an external control signal
The actual value is synchronized every time there is a positive signal edge at the IP 240's
IN input, and the current actual value is stored on every negative signal edge at this input. This
value can be read out as final value (e.g. of a length measurement).
You select the synchronization method you want to use via a control bit. It is thus possible to
specify different methods successively.
Synchronization sets the actual value to the value of the zero offset last transferred (NVER),
irrespective of whether the zero offset in question is an additive or relative zero offset.
10.13.1 Reference Point Approach
A reference point approach synchronizes the measuring system to a reference point in the
traversing range. The location of the reference point is determined by the first zero mark signal
(Z signal) from the incremental encoder that follows a preliminary contact signal.
To generate the preliminary contact signal, you must insert a bounce-free switching element in
the traversing range and connect it to the channel's IN input. Because the IN signal may already be
active at the start of the reference point approach, it is possible to use an existing limit switch as
sensor for the preliminary contact signal.
The encoder used must supply at least one zero mark signal per revolution, and must meet the
timing requirements discussed in Section 13.1.2.
If the channel was configured without backlash compensation, synchronization is possible in both
directions of travel. If the channel was configured with backlash compensation, the actual value is
synchronized only when the preliminary contact is exited with ascending actual value (positive
direction of travel).
Note
You must make sure that synchronization always takes place at the same zero mark
position by selecting the traversing speed during reference point approach and
aligning the negative preliminary contact edge between two zero marks.
Moreover, the direction of travel may not be changed after the negative
preliminary contact edge.
During reference point approach, the Z signal is evaluated while A=1 and B=1.
This state may occur only once for the duration of the Z signal (Z=1).
You will find a list of timing requirements in Chapter 13 ”Encoder Signals”.
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