Function; Reference Point Function - Balluff BML-SB/C/E0-Q-M4-0-KA Serie Manual De Instrucciones

BML-S _ B/C/E0-Q _ _ _ -M4 _ _ - _ 0-KA _ _ /KA _ _-S284
Incremental Magnetic Linear Encoder
3
Construction and function (continued)
3.2

Function

The BML is a magnetic, non-contact, incremental linear
encoder consisting of a sensor head and magnetic tape.
The sensor head and magnetic tape are mounted on the
machine. The magnetic tape contains alternating north and
south poles.
The two incremental sensors in the sensor head measure
the magnetic alternating field. Moving without any contact
over the magnetic tape, the two incremental sensors in the
sensor head sense the magnetic periods, allowing the
controller to detect the travel range.
– To function correctly, the bottom of the
sensor head must always be above the
magnetic tape (see Distances and tolerances
on page 9).
– For a complete technical description and
assembly instructions for magnetic tapes,
please see the magnetic tape user's guide at
www.balluff.com/downloads-bml.
The system is available in several variants:
– With or without a reference point function
– With or without a limit switch function
All functions are implemented via magnetic sampling. The
reference position is integrated in the magnetic tape, limit
switch magnets can be fastened in any position.
Not all variants cover the illustrated functions
and deviations from the illustrations shown may
occur.
3.3

Reference point function

The reference position is the starting position for counting
in each incremental linear encoder.
The way the reference position is detected depends on the
sensor head, the magnetic tape, and the controller.
Advantages of pole-periodic and fixed periodic magnetic
tapes: The magnetic tapes can be purchased in long
lengths and cut individually.
Reference point functions are possible with both linear and
round magnetic tapes (rings, only with BML-S2B/E...
sensor head).
8 english
No or pole-periodic reference signal:
System consisting of:
– BML-S_B/C/E...-M40_-... (none) or
BML-S_B/E...-M42_-... (pole-periodic)
– BML-M...-I4_-...-R0000 magnetic tape
In the most basic linear encoder, the sensor head detects
the magnetic periods using the incremental sensors. The
magnetic tape contains a track with magnetic north and
south poles. The position is detected by the controller by
adding up the counted increments.
With the pole-periodic reference point signal, a reference
point signal is output with each magnetic pole, i.e. every
5 mm. In this case, an external reference switch must be
set at the selected reference point signal. The controller
evaluates the reference position at the moment when the
switch and the reference point signal from the sensor head
are active.
Single or double reference signal:
System consisting of:
– BML-S_B/E...-M41_-...
– BML-M...-I4_-...-R_ _ _ _/0000 (single signal) or
BML-M...-I4_-...-R_ _ _ _/_ _ _ _ (double signal)
magnetic tape
A sensor head with an additional reference point sensor
can output a reference point signal as soon as it reaches
the magnetically coded reference point on the section
track of the magnetic tape. An external reference switch is
not necessary.
Fixed-periodic reference signals:
System consisting of:
– BML-S_B/E...-M41_-...
– BML-M...-I4_-...-C0006/_ _ _ _ magnetic tape
The sensor head with additional reference point sensor can
also be combined with a magnetic tape with fixed-periodic
reference points. Here, the references points are integrated
over the entire length of the tape at specific, uniform
distances, e.g. every 10 cm.
To determine the exact absolute position, the reference run
must be performed up to the external selection switch.