Doc 2136-D01 Rev E 1/24/02
2-8
2-8
Note:
If "IPD" is negative the anode and the cathode of the photodiode must be exchanged.
•
Disable the laser by pressing "ENABLE" (9) button to switch off the laser current.
•
Select constant power (CONST P) with "P" (22).
•
Set the adjust knob (10) completely CCW.
•
Switch on the output by pressing "ENABLE" (9). The LED "ENABLE" (8) lights up, the output is activated, and
the current slowly increases (about 1 s) to the value set with the adjust knob (10).
•
With the adjust knob (10), you can continuously set the photodiode current "IPD", and thus the optical power of
the laser diode, until the laser current "ILD" reaches the selected current limit "ILIM".
If the desired photodiode current "IPD" cannot be set exactly enough with the adjust knob (10), the range of the knob
(10) can be adjusted to the provided photodiode current in wide ranges with the potentiometer "PD RANGE" (24)
(refer to changing the IPD setting range).
If no photodiode is connected or the polarity of the photodiode current was selected incorrectly (refer to chapter
2.3.2), the laser current "ILD" increases to the set current limit "ILIM" after the output is switched on.
If the photodiode current "IPD" is interrupted in constant power mode, the laser current "ILD" increases to the set
current limit "ILIM".
If the laser current "ILD" is limited by the selected current limit "ILIM", ripple and noise no longer correspond to the
specifications for normal operation (refer to chapter 2.3.1). However, the set maximum current "ILIM" cannot be
exceeded.
If the connection to the laser diode is interrupted during operation, the output is switched off automatically. LED
"ENABLE" (8) turns off, LED "OPEN CKT" (6) lights up, and a beeper sounds a short warning signal.
If the output is switched on while the interlock is closed and there is no laser diode connected, at first the LED
"ENABLE" (8) lights up and the output is switched on. Immediately afterwards the LDC 500 recognizes the absence
of the laser diode, switches the output off, the LED "ENABLE" (8) turns off, and the LED "OPEN CKT" (6) lights
up.
After pressing "ENABLE" (9) the LED "OPEN CKT" (6) turns off and the laser diode current output can be switched
on again by pressing "ENABLE" (9).
The laser current can be modulated via the connector "MOD IN" (R3) (refer to chapter 2.3.7).
Changing the "I
PD
" setting range
To guarantee an easy setting of the operating point in constant power mode, even with small photodiode currents, the
full scale of the adjust knob (10) can be set with potentiometer "PD RANGE" (24)between 0.6 mA and 2 mA.
Procedure to change the Ipd range:
•
Turn the potentiometer "PD RANGE" (24) completely CCW. Full scale = 0.6 mA.
•
Turn the adjust knob (10) completely CCW.
