Balluff BML Información Básica página 43

Interfaces for BML Magnetic Encoder System
2
Interfaces (continued)
Optional triggering of VH by an input
Optionally (see sensor user's guide) the differential input
VH can be used to trigger a virtual homing move. This
Req
requires that this input be high for t
timing is shown: Up to time t2 the s_AB position follows
the physical position s_act with an offset. The offset is
undefined as long as no Z-pulse has been sent. At time t0
the input VH goes high. Once at time t1 the time t
Req
expired, the virtual homing move begins after t
time t2 with the same timing as shown in Fig. 2-10.
s_AB
s_act
s_act
1
0
A
B
Z
VH Req
t0 t1 t2 t3
Fig. 2-10: Using input VH
Req
When the sensor is turned on, increments for the virtual
homing move VH are output (see see Fig. 2-9 on
page 14). These increments are also output each time
VH (see Fig. 2-10) is requested.
Req
www.balluff.com
. In Fig. 2-10 the
VH
has
VH
at
VHstart_delay
t
t
t
t
t4
t
Busy Signal instead of Z-Signal
As another option (see user's guide for sensor) a Busy
signal can be output instead of the Z-signal. This tells the
controller at which point the virtual homing move has been
completed. The timing is shown in Fig. 2-11. The virtual
homing move takes the time shown in Fig. 2-10 from t2 to
t4.
Each time the zero position is crossed a new VH Busy
signal is output.
s_AB
s_act
s_act
1
0
A
B
VH Busy
Ub
t0 t1 t2 t3
Fig. 2-11: "VHBusy" mode
Error response in tri-state
When the sensor detects an error it sets its output to high
impedance. The controller can interpret this state as a
cable break.
Once the error is no longer present the sensor behaves
similarly to a switch-on. The timing is shown in Fig. 2-9 or
Fig. 2-11. The error condition ends at time t1. An error will
occur especially when moving out of the tape. Entering the
tape corrects the error. There is no virtual homing move.
Reasons for a virtual homing move
VH (t2 to t4 in Fig. 2-9...Fig. 2-11) is carried out under the
following conditions:
– After switch-on
– When the sensor resumes its normal operating state
after an error
– When there is a request by the input VH
– After running the function Preset
s_AB
t
t
t
t
t4
t
Req
english 15