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7
Tips and Techniques
7.1
Introduction
This section explains operational details of the Model 6100 Laser Diode and
Temperature Controller and provides application examples.
7.2
TEC Limits
The Temperature Controller subsystem has several limits to protect the TEC
from damage. The limits include current and compliance voltage.
7.2.1
Current Limit
There are two types of current limit:
In the first type, the TEC controller processor does not allow the driver
output to exceed the limit's set point via front panel or USB command.
This form of limiting is called the soft limit, and does not affect the
operation of the TEC except to limit the drive current.
In the second type, the high-speed DSP processor monitors the actual
TEC current and if that exceeds the limit set point for any reason then the
output is immediately shut down. This form of limit is called the hard
limit. The Temperature Controller will always be shut down on a hard
limit.
7.2.2
Voltage Limit
The control processor continuously monitors output condition and prevents
overdriving the TEC voltage. When the voltage limit is reached, the
Temperature Controller output current is shut off to prevent damage to the
TEC.
7.2.3
Operating at or Near Io and Vte Limits
Because of the sensitivity of the limit circuits, operating at or near the limit
unless necessary is not recommended. AC line transients, RF interference, or
static can be enough to trigger these limits. Triggers for hard limits and
voltage compliance limits vary, but can include the following:
Static discharges, which may cause enough noise to trigger the circuit.
Turning on the laser when its set point is at or near the limit. Turning on
the output with the set point at the limit can cause a small overshoot in
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