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HA0373T Rev Ck May 2017
Chapter 6
Monitor, Open Loop and Closed Loop
- These three buttons are
used to togg le between Monitor, Open Loop and Closed Loop
modes. The LED in the button is lit when a particular mode is selected - see Section
4.5. for more details.
When operating in '
Monitor
' mode, the X axis (XDIF F) and Y a xis (YDIFF)
difference signals from t he detector, are fed throug h to the rear panel SMA
connectors for use in a monitoring application.
When in ‘
Open Loop
’ mode, the signals at the rear panel are fixed at zero (0V), or
held at the last closed loop value, depending on th e setting of the ‘
Position
Demands In Open Loop
’ parameter in the settings panel (see Section 6.2.). This
is useful when the system is being adjusted manually, to position the light beam
within the detector array.
In ‘
Closed Loop
’ mode, the feedback circuit sends position demand signals (XOut
& YOut) to the rear panel XDIFF and YDIFF connectors, which can be used to
drive a pair of positioning elements (e.g. piezo drivers) in order to position the light
beam within the center of the detector array.
Limits Display
- shows user specified settings for the
parameters listed below.
Axis Limits:
- shows the va lues of the Minimum and
Maximum limits for the XOut and YOut values, between
-10V and +10V. The XOut and YOut values are the signals sent to the X DIFF and
Y DIFF connectors in closed loop mode, which are then used by the position
element to drive the piezo mirror in order to keep the beam central in the detector.
Under normal operating conditions, these values are between -10 V and +10 V
however, some applications may require the limits to be less than this.
PID Gains
- the value of the proportional, integral and derivative constants for the
feedback loop. This term provides the force used to drive the piezo to the demand
position, reducing the positional error. They accept values in the range 0 to 1 and
are set in the Control Settings tab, see section Section 6.2.2.
Settings button
- Displays the 'Settings' panel, which allows the position
aligner operating parameters to be entered - see Section 6.2.
Active
- lit when the unit is operating normally and no error condition
exists.
Error
- lit when a fault condition occurs, e.g. the strain gauge unit is
powered up without a feedback input connected.
Identify
- when this button is pressed, the OLED display on the front panel
of the associated hardware unit will flash for a short period.
