Burkert 8681, Operating Instructions Manual, Page: 129 / 166

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Position Measuring System
20 POSITION MEASURING SYSTEM
Operating principle of the position measuring system
The position measurement is based on recording the change in position of the ferromagnetic target inside
the system. The geometry and the material of the target to be used are synchronized with the sensitivity of
the system.
The measurement precision is determined by the ferromagnetic properties of the target and all other parts
in the system. While the targets must be ferromagnetic, the other components are ideally made of materials
that do not have ferromagnetic properties – see therefor chapter “6.7 Position measuring system data” on
page 27.
The switching positions of the process valves are reported to the actuator by feedback signals from the
solderless position measuring system. Connection to the control head is done by means of a simple adap-
tation to the process valve's piston (valve spindle).
Stroke range / Feedback / Teach functions
The recordable stroke range is between 0 ... 80 mm.
3 discrete feedback are evaluated:
- Position 1 (discrete S1OUT signal)
- Position 2 (discrete S2OUT signal)
- Position 3 (discrete S3OUT signal)
A discrete, external feedback signal (standard proximity switch / external initiator) can also be processed
(S4IN, S4OUT).
The valve positions S1 to S3 are reported within a certain tolerance range, this feedback range can be
adapted - see chapter “6.8.1 Feedback fields (position measuring system)” on page 28.
These Teach buttons or the PC service program (for the 24 V DC, 120 V AC, AS-i, DeviceNet variants) can
be used to define the switch positions of the position sensor (Teach procedure: manual or automatic Teach
functions).
The control head is connected to the PC via the service interface on the electronic module. For the IO-Link
and büS/CANopen variants, the Bürkert Communicator (Type 8920) can be used. This requires a büS stick
in addition to the Bürkert Communicator – see chapter „16 Accessories for büS devices“ on page 120.
If an explosive atmosphere is present the housing may not be opened when voltage is present.
For a detailed description of the electrical installation - see
chapter “10 24 V DC - Design” on page 40 or
chapter “11 120 V AC - Design” on page 47 or
chapter “12 AS Interface - Design” on page 53 or
chapter “13 DeviceNet - Design” on page 62 or
chapter “14 IO-Link - Design” on page 75 or
chapter “15 büS/CAN open-Design” on page 85 or
chapter “18 Connection of an External Initiator” on page 125 or
chapter “19.2 Control head (AS-i) with 2 external initiators” on page 128.
english
Control Head Type 8681