SKS Sweden Bonfiglioli Vectron ACTIVE CUBE ACU 201 Series, Operating Instructions Manual

Page: 113 / 260

09/08
Operating Instructions ACU
111
9.5 Sensor evaluation
In the field of drive engineering, TTL and HTL sensors with 512, 1024 or 2048 divi-
sion marks are widely used. However, other division mark values are used, too.
These division marks (often also referred to as „increments“) determine the resolu-
tion (accuracy) at which a machine can be operated. A “division mark" is defined as
a pulse including the pause following the pulse – the pulse-duty factor is typically
1:1, i.e. with each revolution, a track delivers the number of increments for evalua-
tion. Depending on the characteristics of the sensor and the requirements in the
machine, different degrees of sensor evaluation accuracy are possible. Typical eval-
uation accuracy levels include:
− Single evaluation: One edge of a pulse of a track is counted and evaluated.
− Double evaluation: Two edges (the positive and the negative edge) of a pulse of
a track are counted and evaluated.
−
Quadruple evaluation: A second (offset) track delivers additional edges which
can be evaluated. Any status change of the two tracks is registered and eva-
luated. Thanks to the offset arrangement of the tracks, the direction of rotation
can be detected additionally. The two tracks are commonly referred to as A and
B. Depending on when the edges occur, it can be determined if the motor ro-
tates in clockwise or in anticlockwise direction.
With double or quadruple evaluation, internal calculation for motor control is im-
proved. The number of division marks does not change.
In addition to tracks A and B, sensors often feature a reference track (also referred
to as Z track, zero track, C track). The reference track delivers one pulse per revolu-
tion. This track is used for plausibility checking or for additional functions.
Note: If an operation mode with reference track is selected for the speed
sensor, the frequency inverter will make sure that the Z track occurs
according to the parameterized
Division marks, speed sensor 1
491. If
the evaluation is not consistent, a reaction as per parameter
Operation
mode
760 is triggered.
B
t
A
Z
t
t
1
2
3
4
1
4
Example (quadruple evaluation):
Each edge 1, 2, 3 and 4 is an evaluated signal
within the pulse-pause cycle of Track A. After
that, the cycle is restarted. The type of edges
indicates the direction of rotation:
−
Clockwise direction of rotation: A rising
edge of A (1) is followed by a rising edge
of B (2).
B
t
A
Z
t
t
1
2
3
4
1
4
−
Anticlockwise direction of rotation A rising
edge of A (1) is followed by a falling edge
of B (2).
Track Z: One pulse per revolution
Note:
HTL sensors can be connected to the basic device. The connection of
TTL sensors requires an extension module type EM-ENC.
Operating Instructions ACU 111 09/08