Model 321 Cryogenic Temperature Controller

The Model 321 Cryogenic Temperature Controller includes one sensor input that supports a diode, platinum RTD, or thermocouple sensor. This is factory-configured and can not be changed in the field. For a more accurate measurement, the differential input of the Model 321 allows 4-lead measurement of the sensor.

The Model 321 includes several standard response curves and it has the ability to store one 97-point curve. The accuracy of the Model 321 thermometry can be enhanced with the use of Lake Shore calibrated sensors and CalCurve™ or by the use of SoftCal™¹.

Control software in the Model 321 compares the measured value of the control sensor to the desired control setpoint and acts with the three-term (PID) function to minimize the difference. Control parameters can be entered manually, or the Autotuning feature of the Model 321 can automate the tuning process. Two heater ranges, with the high providing 25 W and the low 2.5 W, allow for a variety of cryogenic cooling systems. The power output of the Model 321 is a quiet, variable DC current, ensuring as little noise coupling as possible between the heater and experiment.

The setpoint ramp feature allows smooth continuous changes in setpoint and can also make the approach to a setpoint temperature more predictable. The zone feature can automatically change control parameter values for operation over a large temperature range. Values for ten different temperature zones can be loaded into the instrument, which will select the next appropriate value on setpoint change.

The built-in serial interface provides remote access to data and stored parameters in the Model 321 and allows setting of most front panel functions. The serial interface of the Model 321 includes the Model 320 command emulation mode for drop-in interchangeability with Model 320 Cryogenic Temperature Controllers in existing systems.