Chapter 3 Laser Diode Driver Module Operation 37
3.5.3.8 Tol Time and Tol Iop
The
Tol Time
and
Tol Iop
elements are used for determining when the laser is “in
tolerance.” The
Tol Time
value is expressed in seconds, and can range from 0.001
seconds to 50 seconds. The
Tol Iop
value is displayed in mA, and can range from 0.1
mA to 100 mA. When operating in
Im
or
Po
modes, The
Tol Iop
setting is ignored,
and fixed values of 50 µA and 50 mW, respectively, are used. The laser is considered
in tolerance after it has been within the tolerance setting for the set number of
seconds. If at any time it goes outside the tolerance range, the time restarts at zero.
As an example, if the
Tol Time
is set to 5 seconds, the
Tol Iop
is set to 2 mA, and
the current set point was 1000 mA, the laser module would have to stay within 998
mA and 1002 mA to be within tolerance. Out of tolerance is indicated by a
Out Of
Tol
status field on the bottom of the Laser Main Screen.
3.5.3.9 Intermittent Contact (Int Control)
The
Int Control
setting controls the detection of intermittent contacts caused by
faults cables or connectors. An intermittent contact, if enabled, will shutdown the
laser with an “open” error. The system allows the user to disable the circuit when
working in an electrically noisy environment that might cause a false detection. The
circuit is automatically disabled in the High Bandwidth Mode.
3.5.3.10 PD Resp
The
PD Resp
element is the conversion factor between photodiode current and
photodiode power, and is expressed in µA per mW. If this value is zero, the system
will not operate in
Po
mode.
3.5.3.11 PD Zero
The
PD Zero
element is the photodiode offset that is removed from the photodiode
read back before any values are displayed, and conversely, is added to any
photodiode set point. The photodiode offset is a combination of any dark current or
stray light picked up while the laser is off. Pressing the
PD Zero
soft key sets this
element to the photodiode current that is present on the photodiode input. To clear it,
simply press the
PD Zero
soft key a second time.
3.5.3.12 Prev soft key
Pushing the
Prev
soft key returns to the previous screen.
3.5.4 Laser Modulation Setup Screen
Newer combo modules (8000-22) have onboard modulation circuits. The modulation
setup screen has six variables,
Mod Enable
,
Mod Frequency
,
Mod Amplitude
,
Mod Type
,
Io min
, and
Io max
.
Mod Amplitude
,
Io min
, and
Io max
are
interrelated, see below.
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