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CEO: Dr. Bernt Götz • Phone +493641/66880 • Fax +493641/668866 • www.piezosystem.com
8.11.2 Trigger Out
In order to control external devices, the measured or desired (setpoint) position can be reported back
via the trigger output. The input signal for th trigger can be chosen via
trgsrc
command.
The trigger signal is low-active, i.e. an H / L edge shows that a trigger point has been reached.
The signal range in which trigger events are generated is determined with
trgss
(lower limit) and
trgse
(upper limit). The interval between the trigger levels is determined with
trgsi
.
Triggering on a rising (
trgedg,1
), a falling (
trgedg,2
) or both edges (
trgedg,3
) is possible; the trigger
is deactivated with
trgedg,0
.
The unit of measurement for
trgss
,
trgse
,
trgsi
is the actuator-specific unit in controlled operation
(e.g. µm or mrad), the duration of the trigger pulses can be set as an integer multiple of 50µs (standard
1 * 50µs). It is important to ensure that trigger pulses do not overlap. If necessary, the duration of the
pulses must be set to the minimum (
trglen,0
) or the travel speed of the actuator needs to be reduced.
Furthermore, it must be ensured that the motion range delimited by
trgss
and
trgse
is completely
traversed (plus 0.2% of the total stroke), otherwise no trigger points are generated as no change in
direction of motion can be detected.
Example: An actuator has a closed loop stroke of 80 µm. With edge = rising (
trgedg,1
),
trgss,10
[µm]
ttrgse,30
[µm]
trgsi,5
[µm] the trigger events are generated at 10 µm, 15 µm, 20 µm, 25 µm
& 30 µm. After reaching the position
trgss
(measured value> = 10µm) the trigger pulse is set and the
next trigger point is calculated (15µm), the trigger is switched off after n * 50µs and it is waited for the
position 15µm to be reached. After reaching this position, the trigger is set again and the next position
is calculated again (20 µm). After reaching 30 µm, the next trigger point is set to 10 µm, the trigger is
only released when the position 10 µm is approached from "below" (i.e. from a position 10µm - (0.2%
of 80µm)).
The edge detection works as follows:
•
With a rising edge, the highest measured value (distance) is always noted.
•
If the measured value falls by more than 0.2% of the distance below the saved distance, a falling
edge is recognized.
•
Now the smallest measured value (distance) is always noted.
•
If the measured value now increases by more than 0.2% of the distance over the noted
(smallest) distance, a rising edge is recognized again.
This functional principle requires that the area delimited by
trgss
and
trgse
is always passed beyond
its limits (at least +/- 0.2% of the way).
8.12 Temperature measurement
To avoid damage to the electronics, the device is switched off at a temperature of 65 °C and can only
be used again after power cycling or resetting by the
reset
command. To check the temperature of the
heat sink in dynamic operation or under bad cooling conditions the temperature can be queried with the
temp
command.
