2.10.3 Sensor Installation
45
|
www.lakeshore.com
2.10.2.1 Sensors Using Standard Curves
Some types of sensors behave in a very predictable manner and a standard tempera-
ture response curve can be created for them. Standard curves are a convenient and
inexpensive way to get reasonable temperature accuracy. Sensors that have a stan-
dard curve are often used when interchangeability is important. Some individual sen-
sors are selected for their ability to match a published standard curve, but in general
these sensors do not provide the accuracy of a calibrated sensor. For convenience, the
Model 372 has several standard curves included in firmware.
2.10.2.2 Curve Handler™
Lake Shore provides a software application, called Curve Handler™, which makes
loading temperature curves into the Model 372 a very simple process. The program
can copy curves from properly formatted files into the Model 372 user curve loca-
tions. You can also use it to read curves from the Model 372 and save them to files.
There are two versions of the Curve Handler™ application. The fully featured version
is a 32-bit Microsoft Windows™ application that must be installed on a Windows™
PC. This version works with the IEEE-488, Ethernet, and USB computer interfaces on
the Model 372, and allows you to manipulate the temperature curves directly in the
program window. This version is compatible with the older format .340 curves and
the newer .CURVE format that is needed to load cubic spline curves. This version will
also work with all existing Lake Shore temperature controller and temperature moni-
tor instruments. The Windows™ version of the Curve Handler™ application is avail-
able, free of charge, from the Lake Shore website at www.lakeshore.com.
The second version of Curve Handler™ is written in the Java™ programming language
and is available through the Ethernet web interface on the Model 372. This version
allows you to copy curves from files to the Model 372, and vice versa, but it does not
allow manipulation of curve data, does not support the newer .CURVE format (needed
to read/write cubic spline curves), and only works using the Ethernet interface. Refer
to section 6.4.4 for details on connecting to the web interface and opening the
embedded Curve Handler™ application.
2.10.3 Sensor
Installation
This section highlights some of the important elements of proper temperature sensor
installation. Information on installing temperature sensors applies equally well to
other resistance measurements. For more detailed information, Lake Shore sensors
are shipped with installation instructions covering that specific sensor type and pack-
age. The Lake Shore Temperature Measurement and Control Catalog includes an
installation section as well. Lake Shore also offers a line of Cryogenic Accessories.
Many of the materials discussed here are available through Lake Shore and can be
ordered with sensors or instruments.
2.10.3.1 Mounting Materials
Choosing appropriate mounting materials is very important in a cryogenic environ-
ment. The high vacuum used to insulate cryostats is one source of problems. Materi-
als used in these applications should have a low vapor pressure so they do not
evaporate or out-gas and spoil the vacuum insulation. Metals and ceramics do not
have this problem, but greases and varnishes must be checked. Another source of
problems is the wide extremes in temperature that most sensors are exposed to. The
linear expansion coefficient of a material becomes important when temperature
changes are so large. Never try to permanently bond materials with linear expansion
coefficients that differ by more than three. A flexible mounting scheme should be