Lake Shore Model 332 Temperature Controller User’s Manual
4.11 SETPOINT
The control setpoint is the desired load temperature expressed in temperature or sensor units. Use
sensor units if no temperature response curve is selected for the sensor input used as the control
channel.
The control setpoint has its own units parameter. Set with the
Control Setup
key in Paragraph 4.7.
Control channel readings can display in any units. Display units need not match setpoint units.
NOTE
: If a curve is not assigned to the control input, control reverts to sensor units and the
setpoint is set to the most current reading.
When changing setpoint units while the control loop is active, the Model 332 converts the control
setpoint to the new control units for minimal disruption in control output.
Setpoint resolution depends on sensor type and setpoint units. With setpoint expressed in temperature,
setpoint resolution is 0.001 degree for setpoints below 100, and 0.01 for setpoints between 100 and
1000. In sensor units, the setpoint resolution matches the display resolution for the sensor input type
given in the specifications (Table 1-1).
The instrument allows a large setpoint range to accommodate a variety of sensors and units. With
setpoint expressed in sensor units, setpoint range is unlimited. The user must determine suitability of a
setpoint value. In temperature units, a safety feature limits the setpoint value to help prevent load
damage load. The setpoint limit in the temperature response curve sets maximum safe temperature in
kelvin for the sensor package. It can be verified by using the Curve Entry key. The setpoint is limited to
a value less than or equal to the limit. If the setpoint value changes from the number entered when
Enter is pressed, it is likely the setpoint exceeds the above limit or is inappropriate for the sensor type.
Once control setup parameters are configured (Paragraph 4.7) and the active control loop is selected
(Paragraph 4.6.1), the desired temperature setpoint is entered by pressing the
Setpoint
key.
Enter for Loop 1
Setpoint +77.350½
The setpoint is entered using the numeric keypad, which includes the numbers 0
–
9, +/–, and decimal
point. Press the
Enter
key to accept the new setpoint or press the
Escape
key to cancel.
If the display format is configured to show the setpoint (Paragraph 4.3), you will see something
resembling the following for a normal display.
À 77.236½ Á 295.22½
 77.350½ 50% Low
4.12 RAMP
The Model 332 generates a smooth setpoint ramp when the setpoint units are expressed in
temperature. The user can set a ramp rate in degrees per minute with a range of 0 to 100 and a
resolution of 0.1. Once the ramp feature is turned on, its action is initiated by a setpoint change. When
a new setpoint is entered, the instrument changes the setpoint temperature from the old value to the
new value at the ramp rate. A positive ramp rate is always entered and it is used by the instrument for
ramps up and down in temperature.
The ramping feature is useful by itself but it is even more powerful when used with other features.
Setpoint ramps are often used with zone control mode. As temperature is ramped through different
temperature zones, control parameters are automatically selected for best control. Ramps can be
initiated and status read back using a computer interface. During computer controlled experiments, the
instrument generates the setpoint ramp while the computer is busy taking necessary data. AutoTune
does not function during a setpoint ramp. The ramp rate disguises the reaction of the cooling system
and no valid tuning data can be taken.
Operation
4-23