
Lake Shore Model 325 Temperature Controller User’s Manual
Operation
4-23
4.12 RAMP
The Model 325 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; it is used by the instrument
for up and down ramps 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.
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. Any subsequent change in setpoint will ramp at the specified rate.
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.
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