3.9 Setup of polarities and bias voltage
LDC340 / Page 23
3.9.2 Polarity of the internal monitor diode (PD POL)
The internal monitor diode can either be used with anode or cathode connected to
ground. If you have chosen the right pins of the output jack you also have to select
the right polarity with the key PD POL in the field SETUP at the front panel.
If the polarity has been chosen correctly the display of the photo current is positive
when driving the laser diode above the threshold current.
If the polarity is chosen wrong the display of the photo current is negative when
driving the laser diode above the threshold current. In this case you
must never
switch on the bias voltage.
3.9.3 Bias voltage of the monitor diode (PD BIAS)
If required the monitor diode may be driven with a bias voltage of 0 ... 10 V.
The bias voltage is switched on by pressing the key PD BIAS for about one second.
Attention
Before switching the bias voltage on make sure that the photodiode
polarity is correct (inverse direction).
If the photodiode is forward biased with a voltage a current will flow
through it that could damage or even destroy it.
NOTE
To protect the monitor diode from accidental biasing the, switch PD BIAS
must be pressed for about 1 second to switch on the bias voltage.
