4.5 Commands
4 – 37
Lock TEC Control Mode When On
TMLK(?)
{
z
}
Set (query) the TEC control mode lock-out
{
to
z
=
(
NO 0
,
YES 1
)
}
.
When
TMLK
YES
is set, the LDC500 will prevent the
TMOD
command
from operating if the laser is on. The front-panel [CT
/
CC] key is
similarly inhibited.
Front panel:
>
1?; 48
.
TMLK?
Example:
NO
TEC Autotune
TUNE(?)
{
z
}
Set (query) the temperature control autotune process
{
to
z
=
(
OFF 0
,
ON 1
)
}
.
The LDC500 implements an automatic tuning algorithm, based on an
“open loop” step-response method. If an autotune cycle is initiated
(by sending the
TUNE
ON
command), the LDC500 will first wait until
the temperature reading is stable, and then generate an output step
in TEC current corresponding to 10% of the user current range (set
by
TILM
). The temperature reponse is then monitored for a period of
time, and loop gain parameters determined.
If the temperature does not stabilize at the beginning of the cycle,
the autotuning fails and the loop parameters remain unchanged. If
the step response cannot be interpreted successfully, the autotuning
also ends in failure and the loop parameters are unchanged. Finally,
if the user cancels an autotune cycle in progress (either by sending
TUNE
OFF
or by pressing the [Clear
/
Cancel] button while the dis-
play focus is at Autotune), then the autotune stops and the loop
parameters are unchanged.
If the TEC module was o
ff
upon receipt of the
TUNE
ON
command,
it will be turned on for the duration of the tuning cycle, and then
returned to o
ff
.
Autotuning can be performed regardless of TEC control mode.
Autotuning can be performed when the sensor model is “none”
(resistance), or in any of the Celsius models. The tuning algorithm
is more robust, however, when using true temperature units instead
of resistance units.
When querying
TUNE?
, the token response is either
OFF 0
(tun-
ing has not been started, or was cancelled),
ON 1
(tuning is in
LDC500 Series Laser Diode Controllers
