THORLABS TNA001/IR User Manual page 24

Chapter 4
8) Depending on the range of tra vel of the pi ezo actuators, it is po ssible that the
piezo range is not suffi cient to drive this stage to the max po wer position and in
this case, the manual actuators should be adjusted to reposition the stage. The
piezo position is indicated by the 'TARGET display as follows:
Using the Target Display
The 'target' display shows the horizontal and vertical position of the piezo actuators,
relative to their mid positions and should be read in conjunction with the SIGNAL and
RANGE bars.
For example, consider the situation when the RANGE bar indicates '4', and the
SIGNAL bar is 2/3 lit. This shows that the current power level is about 70nA. Let's also
assume that the amber LED is lit to the right of the target. This indicates that the
horizontal piezo actuator is towards the right hand side of its travel. The piezo driver
associated with the horizontal actuator will show around 60V (assuming a 75V piezo;
for a 150V piezo, a typical value will be around 120V). Now suppose that after a few
minutes, the power signal increases and the red LED to the right of the target is lit.
This means that in order to locate maximum power, the piezo is moving more to the
right. But, the Red LED also indicates that the piezo is near the limit of its travel to the
right and the associated piezo driver shows about 73V (148V for a 150V piezo). This
means that the piezo actuator must be recentered, and the position error taken up by
manual adjustment.
Fig. 4.3 TARGET and VOLTS Displays Showing Values Near Travel Limit
24 HA0165T Rev 4 May 2012