Setpoint - Lakeshore 335 User Manual

62 c 4: Operation
HAPTER
Model 335 Temperature Controller

4.5.1.7.6 Setpoint

The Setpoint parameter is used to set the desired load temperature for a control loop.
Before a setpoint can be entered, a control loop must be created by configuring an
input sensor and assigning it to a control output using the Control Input parameter.
The Setpoint can be entered in either temperature units or sensor units, based on the
sensor input's Preferred Units setting. The Setpoint Ramping feature is available
when controlling in temperature units to provide smooth, continuous control from
one temperature to the next. Refer to section 4.4 for details on Input Setup. Refer to
section 4.5.1.7.1 for details on assigning a Control Input. Refer to section 4.5.1.7.7 for
details on the Setpoint Ramping feature.
Most applications require control in units of temperature. To control in units of tem-
perature, set the Preferred Units parameter of the control input sensor to either kel-
vin or Celsius. When controlling in temperature, the available setting range of the
setpoint is limited by the Setpoint Limit parameter of the assigned temperature
curve. Refer to section 4.4.11 for details on setting the Preferred Units parameter.
Refer to section 5.8.2 for details on setting a curve Setpoint Limit.
The Setpoint Limit feature only limits the Setpoint entry. For even greater protection, the
Temperature Limit feature can be used to turn off all heater outputs if a sensor reading
above the specified temperature is observed. Refer to section 4.4.10 for details on the
Temperature Limit feature.
There are some instances when temperature control in sensor units may be desired,
for example when a temperature curve is not available. For these applications, the
Model 335 can control temperature in sensor units. To control in sensor units, set the
Preferred Units parameter to sensor. When controlling in sensor units, the Setpoint
resolution matches the display resolution for the sensor input type given in the speci-
fications (section 1.3).
Temperature control in sensor units can be unpredictable since most sensors do not have
a linear response to temperature, and therefore have can have different sensitivity in dif-
ferent temperature ranges.
When changing the Preferred Units from sensor to temperature (kelvin or Celsius), or
from temperature to sensor, the Model 335 converts the setpoint to the new control
units by using the assigned temperature curve. This provides minimal disruption in
the control output when changing the Preferred Units parameter while the control
loop is active.
Menu Navigation:
SetpointQ(See note below)
When controlling in temperature, the setpoint is limited by the control input tempera-
ture curve's Setpoint Limit. When controlling in sensor units, the setpoint is limited by the
limits of the configured control sensor.
Default: 0.0000 K
Interface Command: SETP