O P E R A T I O N S
Operating the TE Controller from the Front Panel
32
LDC-3700C Series
C H A P T E R
2
used over their linear range, the constants C1 and C2 are used in this case to
determine a linear approximation of the temperature, rather than the Steinhart-
Hart non-linear approximation which applies for thermistors. The appropriate
algorithms are automatically implemented whenever the sensor type is selected
via the rear panel
SENSOR SELECT
switch.
Setting TE Control Loop Gain
For best temperature control loop performance, the control loop gain needs to be
set. The GAIN function sets the analog feedback gain which, in part, determines
how fast the actual temperature reaches and settles to the set-point temperature.
If the gain is set too low (1 is lowest), the TE cooler will take longer to reach the
temperature set-point. If it is set too high (300 is highest), the actual temperature
may overshoot and may oscillate around the set temperature resulting in long
temperature settling times. The allowed GAIN values in the LDC-3700C's
Temperature Controller are: 1, 3, 10, 30, 100 and 300. These values define the
proportional loop gain of our hybrid P-I temperature control loop.
The gain setting depends on the type of TE module and thermal load that you are
using, but we can suggest guidelines for selecting the proper gain. Set the gain to
1 and increase it until the actual temperature oscillates around the set
temperature. Then reduce the gain to the next lower value.
To set the gain, press the
(PARAMETER) SELECT
switch until the
GAIN
indicator
is lit. The
TEC
display will show the value of the control loop GAIN. To change the
GAIN
, press and hold in the
SET
switch, at the same time turn the
ADJUST
knob
until the desired new value is on the TEC display, then release the
SET
switch.
When the
SET
switch is released, the new value will be stored in non-volatile
memory.
At this point the sensor type is selected, the appropriate constants are entered
and the temperature control loop gain is set. Next, the display will be configured to
read in the correct units for operation in Constant Temperature mode. The
enunciators next to the TEC display will indicate the display mode corresponding
to the switch pressed (°C will illuminate when the T push button is pressed).
The
TEC DISPLAY
section
is used to select the displayed temperature,
T
, sensor
value,
R
, or TE module current,
I
TE
. Press
T
for temperature and the display will
indicate measured temperature in °C. When the
R
switch is pressed, the display
will show the measured thermistor resistance in k
,
the measured LM335 voltage
in mV (not annunciated), or the measured AD590 current in µA (not annunciated),
TE
LIM I
SAVE
CONST
GAIN
LIM T
HI
TEC
LIM I
CAL PD
LIM I
LIM P
RECALL
SET
SELECT
PARAMETER
LASER
Summary of Contents for LDC-3700C Series
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Page 8: ...L I S T O F FIG U R E S vi LDC 3700C Series...
Page 10: ...L I S T O F TA B L E S viii LDC 3700C Series...
Page 78: ...RE M O T E O PE R A T I ON Command Syntax 62 LDC 3700C Series C H A P T E R 3...
Page 150: ...C O M M A N D RE F E R E N C E Command Reference 134 LDC 3700C Series C H A P T E R 4...
