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Lake Shore Model 331 Temperature Controller User’s Manual
4.12 RAMP
The Model 331 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.
NOTE: When an incomplete ramp is shut off, the setpoint will remain on the most current
setting, i.e., the reading will not jump to the end of the ramp.
NOTE: If the input type or input curve is changed while a ramp is in progress, both ramping
and the heater are turned off.
NOTE: If Ramp is on and the setpoint is set to sensor units, the ramping function will remain on but
when another setpoint is entered, the setpoint goes directly to the new setpoint value. The
Ramp LED will stay on solid (no blinking).
To enable setpoint ramping, press the Control Setup key, then press the Enter key until you see the
following display.
Select for Loop 1 °®
Setpoint Ramp On
Use the s or t key to select Setpoint Ramp On. Press the Enter key. You will see the following.
Enter for Loop 1
Ramp Rate
0.0 K/m
The ramp rate is entered using the numeric keypad, which includes the numbers 0 – 9 and decimal point.
The user can set a ramp rate in degrees per minute with a range of 0 to 100 and a resolution of 0.1.
Ramp rate will be in the same units specified for the setpoint. Press the Enter key. The front panel
Ramp LED will illuminate, indicating the ramp function is active. Any subsequent change in setpoint will
ramp at the specified rate and the Ramp LED will blink while ramping is in progress.
If you wish to pause a ramp, press the Setpoint key then immediately press the Enter key. This stops
the ramp at the current setpoint but leaves the ramping function activated. Then to continue the ramp,
enter a new setpoint.
To turn the ramping feature off, press the Control Setup key, then press the Enter key until you see the
following screen.
Select for Loop 1 °®
Setpoint Ramp Off
Use the s or t key to select Setpoint Ramp Off. Press the Enter key then the Escape key. The Ramp
LED will turn off.
Operation
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