Control Head Type 8681
PositionMeasuringSystem
16. 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. Ideally materials are used which do not have any ferromagnetic properties.
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 adaptation to the process valve's piston.
Stroke range / feedback signals / teach-in function
The recordable stroke range is between 0 ... 80 mm.
3 discrete feedback signal are evaluated:
- Position 1 (discrete S1OUT signal)
- Position 2 (discrete S2OUT signal)
- Position 3 (discrete S3OUT signal)
3 Teach-In buttons have been provided for comparison with the actual stroke range (see Chapter “16.1. Setting the position measuring system (Teach-In)”). The switching positions for the position measuring system can be
determined with these Teach-In buttons or by means of the PC service program (connection via the Service interface on the electronics module).
A discrete, external feedback signal (standard proximity switch) can also be processed (S4IN, S4OUT).
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” or
Chapter “11. AS Interface - Design” or
Chapter “12. DeviceNet - Design” or
Chapter “13. 120 V AC - Design” or
Chapter “15.2. Control head (AS-i) with 2 external initiators”.
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