2 – 12
Getting Started
If a new limit value is more restrictive than the present setpoint, the
setpoint is “dragged” along with the limit value. For instance, if the
temperature setpoint in CT mode was 15.000
◦
C, and then the mini-
mum temperature changed from 10.000
◦
C to 18.000
◦
C, the setpoint
will automatically follow up to the new minimum. Conversely, at-
tempting to change a setpoint outside of the present values of the
limits will fail. For example, if the current setpoint in CC mode is
1.000 A, and the current limit is 2.000 A, an attempt to change the
current setpoint to 2.125 A will fail. Stated another way, limit values
always have priority over setpoint values.
2.2.9
Monitoring the TEC
The TEC controller’s working status may be monitored with the
alphanumeric display. Press the TEC [Monitor] button, and then use
[ ] and [ ] to step between monitoring the TEC current, TEC voltage,
temperature, and raw sensor output.
Items displayed on the Monitor tree are read-only.
2.2.10
Configuring TEC trip-offs
Under certain limit conditions, it is important to shut down the TEC
controller output. To customize which events will lead to TEC shut-
down, press the TEC [Config] button, and then press [ ] until you
reach the first “TE Cfg: Trip-OFF” item.
Specific events can be armed to shut down the TEC controller by
setting the “Trip-OFF” selection to “Y”; the events will be ignored
for shut-down by selecting “N.”
•
To shut down if the TEC current reaches its limit value, set
“Trip-OFF at TE Ilim:” to “Y.” Note that for normal operation,
this event is typically left at set to “N,” as the current source
will never output a value greater than the programmed limit—
the e
ff
ect of reaching the limit is to “saturate” the temperature
control loop, which will often happen during large temperature
setpoint changes.
•
To shut down if the TEC voltage reaches its limit value, set
“Trip-OFF at TE Vlim:” to “Y.” This is an important limit, and
should only be disabled by experienced users.
Note: there is no
CAUTION
voltage-limiting in the TEC current source, so disabling the Vlim
trip-OFF can lead to distruction of the user’s TEC module.
•
To shut down if the temperature goes above
T
max
, set “Trip-OFF
at Tmax:” to “Y.”
LDC500 Series Laser Diode Controllers
