Proper handling of switches and linear position transducers
High pressure inductive proximity switches
If required, hydraulic cylinders from AHP Merkle are equipped with inductive proximity switches that are pressure-tight up to 500 bar (7250 PSI). The switches are protected against polarity reversal and short-circuit as standard.
If hydraulic cylinders are ordered with inductive proximity switches, the sensors are mounted and adjusted ready for operation. It is not permitted to tamper with the proximity switches, otherwise all warranties will become void.
If such a proximity switch has to be exchanged in the course of maintenance work, it is essential to ensure that it is adjusted properly. To do this, move the piston to the position to be monitored, turn the new proximity switch with its front side carefully to the stop, and then turn it back again 360°. This achieves the required switching distance of 1 mm (0 .039 inches) Then lock it using the lock nut.
Tip: With hydraulic cylinders from AHP Merkle, the standard sensing point is the cylinder end position. It is possible to shift the sensing point up to 5 mm (0.2 inches) before the piston end position. The customer has to specify such special requirements clearly already when the hydraulic cylinder is ordered, because no subsequent adaptations are possible.
Adjustable inductive proximity switches
As an alternative to the high pressure inductive proximity switches there is also the option of adjustable inductive proximity switches. These are not pressure-tight, and detect the cylinder stroke via a rod that extends out of the pressure chamber to the rear.
These sensors are protected against polarity reversal, but NOT protected against short-circuit.
Magnetic field sensors
The magnetic field switches are very easy to adjust using the slot mounting.
For exact positioning the switch is slid towards the permanent magnetic field generated by the piston until it switches (image 1). Mark this position.
Repeat the same procedure at the end of the magnetic field and conclude it with a corresponding mark (image 2). Finally, position the switch in the middle between the two marks and fix it in place (image 3).
Because of their mode of operation, magnetic field sensors have a relatively wide switching range.
Adjust magnetic field switches
Mechanical limit switch
Mechanical limit switches are actuated via an external stop or a switch cam. If the switch is actuated via a switch cam, the switching position can be changed subsequently. The switches are notable for their high switching current carrying capacity.
Linear position transducer
When installing a linear position transducer, pay very close attention to ensuring that after assembly the linear position transducer and the hole in the piston and piston rod are optimally aligned; this prevents crushing or other damage. The simplest way to do this is to move the piston to the piston end as far as it will go and only then push the linear position transducer through the hole.