CL-200A Manual, Rev. 120523
12
the probability of overheating the experiment to the point of damage. There is no protection from
overcooling caused by a misplaced monitor thermistor.
An indicator on the front panel indicates an open-thermistor fault of the selected feedback
thermistor. Normally if a thermistor becomes open, as with a broken wire, the controller sees this as
a lower temperature. The controller will then increase the output power to try to raise the
temperature. This can cause overheating of the experiment if the fault is not noticed. In the
CL-
200A
, the selected feedback thermistor is monitored for an open condition. If an open fault is
detected, the output power is shut off, preventing overheating. A red LED indicates the presence of
an open thermistor.
MANUAL MODE
In
manual mode
, the
MANUAL VOLTAGE
control (Item K) is used to set the output voltage to a
fixed value. In
manual mode
, the
SET TEMPERATURE
control (Item H) is disabled, as is the feedback
system of the
CL-200A
.
Operation is again straightforward. Set the
CL-200A
to accept
internal commands
by setting the
INTERNAL
/
EXTERNAL SELECT
control (Item J) to
internal
. Place the
CL-200A
into
manual mode
by
switching the
COOLING MODE SWITCH
(Item C) to
manual
. Switch the
METER
(Item B) to
Output Volts
and adjust to the desired set-point using the
MANUAL VOLTAGE
control (Item K).
Alternatively, the
CL-200A
can be commanded using external inputs. Set the
CL-200A
to
external commands
by setting the
INTERNAL
/
EXTERNAL SELECT
control (Item J) to
external
. In this
mode the
CL-200A
will accept external voltage commands at the
EXT VOLT SET
BNC (Item T) located
on the instrument rear panel.
In this mode, the instrument operates as a 0-15 VDC power supply that can provide up to 5A of
current to each channel. Use this mode with heater systems that will operate properly with a fixed
voltage and lack of feedback thermistors.
The
CL-200A
has a convenient feature for switching modes. In the
CL-200A
, the control loop
integrator is held at its last value when switching to
off
, allowing the integrator to resume when the
Automatic mode is again selected.
When the
CL-200A
is switched to
manual
mode, the integrator tracks the manual voltage.
When the mode is set from
manual
to
off
, this value is held. Switching to automatic mode allows the
control loop integrator to begin at the last voltage setting of the manual mode. This allows the user
to set the integrator to any desired initial value for the automatic mode.
Warner
Instruments
A Harvard Apparatus Company