Balluff BML-S1F Series, User Manual, Page: 42 / 130

16
6
Interface (continued)
6.2 Digital rectangular signal
(BML-S1F_- Q …)
The sensor head converts the sine and cosine signals from
the incremental sensors in digital A/B impulses and
transfers them to the controller.
6.2.1 Digital incremental measuring system
The sensor transmits the measurement to the controller as
a differential voltage signal (RS422).
The edge distance A/B corresponds to the mechanical
resolution of the sensor head (e.g. 1 µm). The time
between two edges is defined by the minimum edge
distance and must be adjusted to the controller. The
maximum movement speed is defined by the mechanical
resolution and the minimum edge distance (see Tab. 6-1
and Tab. 6-2).
Fig. 6-3:
A
B
Z
Digital output signals for forward movement
The digital A/B impulses are interpolated in the sensor head.
The two digital impulses A and B are electrically phase-
delayed by 90°, the algebraic sign of the phase difference
depends on the direction of movement of the sensor
(Fig. 4-1/Fig. 4-2).
Each edge change of A or B is a counting step for the
cycle counter (up/down counter). With a leading signal A,
the counter reading increases and it decreases with a
leading signal B. The controller knows the precise
increment position at all times, without having to
periodically query the sensor (real-time capability).
The position of the Z signal may be different in the position
measuring systems (Q1 to Q4, see Fig. 6-3). It is, however,
always one increment wide.
If the sensor is supplied with voltage that is
isolated from the processing electronics, the
GND for this voltage must be connected to the
GND of the processing electronics.
For correct function, the A and B signal must be
evaluated depending on the direction.
Signal periods 360° el.
Edge distance
Reference impulse
Q1 Q2 Q3 Q4
Fig. 6-4:
Signal A
Signal B
Forwards Backwards
Increment
Counter
reading (e.g.)
Direction of
movement
BML output signals with cycle counter
Fig. 6-5:
+A
–A
Circuitry of subsequent electronics (RS422)
A channel
PLC Sensor head
E.g.
IC 26C32
BML-S1F_-A/Q _ _ _ -M_ _ 0- _ 0-…
Incremental Magnetic Linear Encoder
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