Lake Shore 350, User Manual

Page: 16 / 192

2 c
HAPTER
1: Introduction
Model 350 Temperature Controller
In short, the Model 350 cryogenic temperature controller brings a new level of power,
precision, and performance to critical low temperature physics research. It is ideal for
use with He-3 systems, adiabatic demagnetization refrigerators (ADRs), certain dilu-
tion refrigerators, and many other applications demanding low thermal power and
high measurement precision.
1.2 Application
Versatility Designed to support a broad range of sensor types, the Model 350 is performance
optimized for use over the entire temperature range of Cernox™ sensors, making it
the instrument of choice for ULT environments, as well as other cryogenic systems
where errors due to magneto-resistive or radiation effects need to be minimized.
1.2.1 Four Standard
Sensor Input Channels The Model 350 comes with four standard sensor inputs supporting Cernox™, ruthe-
nium oxide, platinum RTDs, and other NTC RTD sensors. Inputs can be configured to
accept any of the supported input types. Each sensor input channel has its own cur-
rent source, providing fast settling times. The four sensor inputs are optically isolated
from other circuits to reduce noise and to provide repeatable sensor measurements.
Current reversal eliminates thermal electromotive force (EMF) errors in resistance
sensors. Nine excitation currents facilitate temperature measurement and control
down to 100 mK, with the nominal temperature range (using Cernox™ sensors) span-
ning to 420 K. The instrument automatically selects the optimal current and gain lev-
els for you once the sensor type is selected, and automatically scales current to
minimize self-heating effects at low temperatures. The patented input circuitry elim-
inates any errors associated with grounding inconsistencies, making it easier to
achieve reliable measurements at ultra-low temperatures. With the ability to label
each sensor input channel with a customized name, it’s also easy to identify the mea-
sured values being displayed.
1.2.2 Three Option
Cards for More Inputs
and a Wider Range of
Applications Field installable input option cards can expand your sensor selection to include sili-
con diodes (like DT-670), capacitance sensors or thermocouples. Once installed, the
option input can be selected and named from the front panel like any other input
type. These option cards further expand the application versatility of the Model 350
temperature controller by allowing specialized sensors to be switched in and out to
achieve specific measurement objectives. For example, addition of the thermocouple
input option enables continuous measurement to 1000 K and above. Alternatively,
the capacitance sensor option card enables a magnetics-impervious capacitance
temperature sensor to be temporarily switched in for elimination of magneto-resis-
tive effects while taking low temperature sample measurements under high or
changing fields. Diode sensor support is provided by the 4-channel scanner option
card, which also enables use of additional Cernox™ sensors for supplemental

monitoring.
1.2.3 Four PID
Controlled Outputs For convenient integration into a wide range of systems, the Model 350 offers four
PID-controlled outputs. Variable DC current source outputs include a 75 W output for
direct control of the typical main warm-up heater, and a 1 W output for fine control of
the sample heater. Two additional 1 W variable DC voltage source outputs can be
used to power auxiliary devices like a still heater in a dilution refrigerator, or to con-
trol a magnet power supply driving an ADR. The ability to dynamically select an input
to associate with the controlled output provides additional flexibility in setting up the
control scheme.