IFM MK59 Series, Operating Instructions Manual

Page: 7 / 33

Cylinder sensor with IO-Link MK59xx
7
5 Function
The device provides the following functions and signals them with a switching signal:
• monitoring the piston position in pneumatic cylinders.
• diagnostic functions:
– Stroke time monitoring (
Ò /
21)
– Switching cycle monitoring ( Ò / 23)
– Magnetic field monitoring ( Ò / 24)
Depending on the device type, one or two physical switching outputs are available:
T-slot sensors Number of switching outputs
MK5904, MK5907, MK5908, MK5909 2
MK5905, MK5906 1
5.1 Measuring principle
The device measures the magnetic field in 2 spatial directions (B
x
and B
y
) and calculates the absolute
magnetic field (B
abs
) and a position-dependent signal [PDV1].
The absolute magnetic field must be in the range of 1 mT...20 mT.
Bx
By
B abs
B
x
: Magnetic field in x-direction
B
y
: Magnetic field in y-direction
B
abs
: Absolute magnetic field
If the magnetic system is designed accordingly, the calculated output signal is linear and proportional
to the position of an encoder magnet.
Ferromagnetic materials (iron), permanent magnets and magnetic fields in the vicinity of the
device or the encoder magnet can influence and falsify the signal.
5.2 Signal range
The device provides a measured value [PDV1] depending on the position of the encoder magnet in
the range of 0...4000. This value is dimensionless, but proportional to the position of the encoder
magnet.
The output signal corresponds to the value 2000 when the encoder magnet is centred under the target
marking "T" on the sensor. Due to the shape of the encoder magnet and the distance between the
device and the magnet, different slopes of the signal curve as well as different resolutions and
measuring ranges can be achieved.
The longer a magnet is, the lower the slope of the signal curve and the resolution and the larger
the measuring range becomes.
If the magnets are too weak or the distance between the device and the magnet is too great, the
signal range may be limited at the edges if the magnetic field is too weak.
If the magnets are too strong or the distance between the device and the magnet is too small,
the signal range may be interrupted in the middle if the magnetic field is too strong.