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HA0365T Rev D Jan 2017
Chapter 5
5.6.4 Setting the Position Sensor Zero
On actuators with position feedback, the position sensor is a strain gauge fitted to the
piezo actuator. The strain gauge may give a small signal when the actuator is at zero
position with zero volts applied (due to limitations in manufacture, or temperature
fluctuations). This 'offset' signal must be removed before the position attained by a
specific applied voltage and the p osition attained by a corresp onding specified
distance can be rationalized.
Each actuator has a un ique offset valu e. Therefore the offset should be a djusted
whenever an actuator is replaced. Temperature and prolonged use can affect the
performance of the strain gauge and therefore the offset value.
Each time the Strain Gauge K-Cube is powered up, the display will flash a default
reading until the position sensor is zeroed.
To zero the position sensor:
1) Ensure that the Piezo Driver K-Cube output is zero. Turn the OUTPUT control to
minimum and remove any input on the rear panel EXT IN connector.
2) Either press and hold the button on the Strain Gauge K-Cube, click the ' Zero'
button in th e Strain Gauge K-Cube GUI panel, or call the 'SG_Z eroPosition'
method in the application software.
3) The display on the Strain Gauge K-Cube shows ‘
nULL
’ and counts down to zero.
5.7 Adjusting the Piezo Position
1) Make connections as detailed in Section 5.6.1. or Section 5.6.3.
2) Set the Strain Gauge K-Cube to ‘Position’ mode - see handbook
ha0144 Strain
Gauge K-Cube
.
3) Rotate the Piezo Drive K-Cube ‘Output‘ control clockwise. Notice how the voltage
display increments to sh ow the increasing voltage applied to the piezo. The
Position display on the Strain Gauge Reader K-Cube shows a propo rtional
increase in position (in microns).
4) Rotate the ‘Output’ control an ticlockwise. Notice ho w the voltage display
decrements to show the decreasing voltage applied to the p iezo. The Position
display on the Strain Gauge Reader K-Cube shows a proportional decrease in
position (in microns).
Note
The position of the actuator is relative to the minimum position set for the
arrangement using the ‘Null’ facility, see Section 5.6.4. The extension of
the actuator is displayed on the Strain Gauge K-Cube as a position in
microns.