Connecting The Interlock - THORLABS ITC1 Series Operation Manual

4 Operating Instruction

4.4 Connecting the Interlock

The interlock represents a current source (output pin 1 of ST2 resp. C17 of ST1), with the re-
turn pin 5 (ST2) or C14 (ST1). The voltage between pin 1 and 5 (or C14 and C17) is observed
and used for enabling / disabling the output of the laser current controller.
Below are shown possible external connections to the interlock:
The voltage across the interlock pins must not exceed ~ 2.5 V, otherwise the interlock is con-
sidered as open. For this reason, the resistance of the external interlock circuit must be
W
between 0 and 430 .
It is also possible to connect an LED (current through the LED is about 3.5 mA) as shown in the
right diagram. In this case the LED serves as an additional signal that the laser current is
switched on.
When the laser current is switched on, the interlock is checked - if it is open, the laser cannot
be switched on. If the interlock is interrupted during laser operation, the laser is shut down im-
mediately, so the interlock circuit can be used for emergency switch-off of the laser current as
well.
When using the ITC1xx with Thorlabs laser diode mounts, the interlock function is provided by
the mount. For details please see the Operation Manual of the used laser diode mount.
© 2018 Thorlabs GmbH 19