40
HA0165T Rev 4K Sept 2017
Chapter 6
If 'mW' is selected, readings are displayed or returned as power, generated using
a Amp:Watt calibration factor specified either in the 'Settings; panel or by calling
the SetUnitsMode method.
If ‘dB’ is selected, readings are displayed or returned in dBs. The signal is first
converted to Watts according to th e calibration factor, and then into dB.
Consequently, this conversion is also wavelength dependent.
If the rear panel ‘SIG IN’ SMA input is connected (input source is set to a SMA mode
using the SetInputSrc method), the display can be configured to display 'V', '%' or
'User'.
If 'V' is selected, readings are displayed or returned in Volts, i.e. the raw input
signal to the rear panel ‘SIG IN’ SMA connector.
If '%' is selected, readings are displayed or returned as a percentage of full scale
input, e.g. a 5V signal will display a value of 50%.
If 'User' is selected, readings are displayed or returned as a calibrated value using
a calibration factor set using the SetInputSrc method (or the Voltage calibration
parameter on the Input/Output tab of the Settings panel), e.g. if the calibration
factor has been set to '20', a 5V signal will display a value of 10.
Display Averaging
- displays the averaging level being applied to the power readings
(and the relative display bar) displayed on the GUI. Settings of 'low', 'medium' and
'high' resulting in averaging numbers of 5, 10 a nd 20 respectively. At the default
display update rate of 10Hz, this translates to 0.5, 1 and 2 second time constants
respectively. This setting is provide d as a conve nient way of smoothing readings
displayed on the GUI only, and does not affect in any way those same readings when
returned by software messages.
To change the setting, click the required setting button.
Circle Diameter control
- used to ad just the diameter of the scan circle, when
operating in 'Manual' adjustment mode. The current diameter is displayed in the
'Settings' window. Note. Use of this con trol will automatically switch the circle
diameter adjustment mode to 'Manual'.
Relative Signal Power -
The max power located in th e alignment. Bar display
showing a convenient visual indication of the feedback signal level. When the input
source is set to TIA (PIN), the bar display indicates the power level with respect to the
currently applied range. E.g. if the TIA range is 1micron, then a bar displaying half
length equates to a power level of 0.5micron. When the input source is set to SMA
(‘SIG IN’) i nput (voltage), then bar display indicates the voltage being measured
relative to 10V full scale.
A percentage figure if the max signal level is also displayed.
Note
This is not intended to be a calibrated power reading, but rather a
convenient mechanism for converting current to power. The conversion
factor is typically wavelength specific.