15

SETTINGS SCREEN

Press to access the Settings Screen

Move the slider bar on the touchscreen to change the display

brightness. Press the blue text to toggle the

Beeper on-off

setting.

Figure 21. Settings Screen

LOCK OR UNLOCK SETTINGS

(OPTIONAL)

Settings are not locked.

This is the default. Critical values set with the

Adjustment knob can be locked. Press to lock

the settings.

Settings are locked.

Press to unlock the settings.

Settings are locked and password protected.

Locked settings that are password protected

can only be locked and unlocked using a remote

computer.

EXTERNAL MODULATION

(EXT MOD) BNC

This is the external modulation input. The voltage input on

this BNC sums with the DC value on the screen. The input

impedance is 1 kΩ. To calculate the external modulation

signal voltage, see the next section for the transfer function,

and use the following equation:

V

EXT_MOD = ISETPOINT / Transfer Function

If the external modulation input causes the driver to reach the

current limit, the output signal will be clamped at the limit level

but will not switch off.

The bandwidth of the Current Monitor is lower than the

bandwidth of the output. To monitor the actual output

waveform at high frequencies, connect an oscilloscope across

the output pin on the MONITOR D-SUB, Pin 8 (positive), and

Pin 9 (ground) while using the resistor test load.

CAUTION: Connect the oscilloscope across the

test load only — never connect the oscilloscope

across a quantum cascade laser.

EXTERNAL MODULATION BNC

TRANSFER FUNCTIONS

The external modulation transfer function depends on the

QCL instrument model and is as follows:

QCL500 LAB:

0.1 A / V.

QCL1000 LAB:

0.2 A / V.

QCL1500 LAB:

0.3 A / V.

QCL2000 LAB:

0.4 A / V.

The input range is always -5 V to +5 V.