OPERATION
LDC-3900 Front Panel
10_15 LDC-3900 Series 17
CHAPTER 2

For more information on low level interface commands such as LLO, refer to the
IEEE488.1 specification.
When the instrument is in LOCAL mode, pressing the LOCAL switch causes the
GPIB address to be displayed. The GPIB address may be changed by turning the
ADJUST knob while also pressing the (PARAMETER) SET switch. The usable
GPIB address range is 1-30.
The TALK/LISTEN indicator is illuminated whenever the instrument is
communicating over the GPIB bus.
Adjust Section
The Adjust section is located on the right side of the LDC-3900 Modular Laser
Diode Controller front panel. It consists of the Adjust (main control) Knob and the
LAS/TEC adjust mode enable switches. A green (LAS) or (TEC) LED indicates
that a corresponding module is available for adjustment.
The Adjust Knob is used to change the set points, enter parameter values, enter
the GPIB address, or enter instrument calibration data.
The (Adjust) LAS/TEC switches are used to enter or exit LAS or TEC adjustment
mode. If the (Adjust) LAS/TEC switch is pressed so that the (Adjust) TEC Indicator
LED is orange, the unit enters TEC mode. Likewise, if the (Adjust) LAS/TEC
switch is pressed so that the (Adjust) LAS Indicator LED is orange, the unit enters
Laser adjust mode.
Only one (or none) channel Adjust mode, TEC or LAS, may be operating at any
given time. In order to use the Save or Recall functions, both the TEC and LAS
(Adjust) modes must be disengaged (no Adjust Indicators lit in orange).
The GPIB address adjust mode may be entered at any time (except during
calibration) by pressing the (GPIB) Local switch. This adjustment mode overrides
any other existing adjustment modes. When the GPIB address adjustment is
done, the previous adjustment mode will be reinstated.
Automatic Set Point Adjustment
If the Adjust Knob is turned during operation, while a measured TEC value is
being displayed and the (Adjust) TEC Indicator is orange, the TEC display will
indicate the set point of the selected operating mode (T, R, or I
TE
). This control
mode set point display will continue for three seconds, and then the display will
revert to its former state (a measured value).
For example, assume that an (Adjust) TEC mode is in effect and T is selected as
the TEC Mode, but the (TEC Display) R switch is selected and the sensor
(thermistor) resistance is displayed on the TEC display. If the Adjust Knob is
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