5. 4 B i po l ar C o nt r o l 77
| www.lakeshore.com
5.4 Bipolar Control
The most common type of temperature control output device is a resistive heater,
which requires only unipolar output, since they will add heat regardless of the polar-
ity of the excitation voltage. There are, however, temperature control devices that are
bipolar. These devices, such as thermoelectric devices, can work in both polarities,
moving heat from one side of the device to the other when a current is applied. There-
fore, a surface can be heated or cooled using a bipolar temperature control device. For
these types of bipolar devices, the Model 336 features a bipolar control mode. In this
mode, the Model 336 is configured to drive these devices to control temperature
using Output 3 and 4. Refer to section 2.11 for more information about thermoelec-
tric devices.
To use Output 3 and 4 for bipolar control, first set the Heater Output Type parameter
to Voltage, then set the polarity to Bipolar. The Closed Loop PID control mode can then
be used to control a thermoelectric device, providing a control output of
-10 V to +10 V. Refer to section 2.11 for information on thermoelectric devices. Refer
to section 3.8.5.4 for information on scaling the output for voltages less than 10 V.
Menu Navigation:
Output SetupQOutput (3 or 4)QPolarity (Bipolar)
Interface Command: ANALOG
5.5 Warm Up
Supply
Warm Up Supply mode is designed for controlling an external power supply used for
rapidly increasing the temperature in the controlled system, for example, to bring a
system to room temperature in order to change samples. Refer to section 3.8.5 for
information on using an external power supply for warm up supply mode.
The Control Input parameter determines which sensor is used for feedback in the
Warm Up Supply mode. Refer to section 4.5.1.5 for details on the
Control Input parameter.
Once Warm Up Supply Mode is configured, press Setpoint and set the desired tem-
perature, then press Heater Range and set the range to On to activate the output. The
front panel display must be configured to show the Warm Up control loop for the Set-
point and Heater Range keys to be used. Refer to section 4.2 and section 4.3 for
details on front panel keypad operation and display setup.
The Power Up Enable feature determines if the output will remain on after power is
cycled. Refer to section 4.5.1.2 for details on the Power Up Enable feature.
Menu Navigation:
Output SetupQOutput (3 or 4)QOutput ModeQWarm Up Supply
Interface Command: OUTMODE
5.5.1 Warm Up
Percentage
The Warm Up Percentage parameter is used to determine the amount of voltage to
apply to the unpowered output (3 or 4) when using Warm Up mode to control an
external power supply. The voltage applied will be the full scale output (+10 V) times
the Warm Up Percentage. For example, if the Warm Up Percentage is set to 50%, the
control output voltage for the given unpowered output will be 50% of 10 V, or 5 V,
when the output is on.
Menu Navigation:
Output SetupQOutput (3, or 4)QWarm Up PercentageQ(0% to 100%)
Default: 100%
Interface Command: WARMUP
To Next Page
Loading...
