sales@lakeshore.com, service@lakeshore.com.


There are three aspects of using a cryogenic temperature sensor which are critical to its optimum performance. The first
involves the proper mounting of the sensor package, the second relates the proper joining of sensor lead wires and connecting
wires. The final concern is the thermal anchoring of the lead wires. Although the sequence in which these areas should be
addressed is not set in stone, all elements covered under each aspect should be adhered to for maximum operating
capabilities of the sensor.

SENSOR MOUNTING
The CX-10XX-CU package combines a standard SD sensor with a gold-plated copper mounting bobbin to form the CU
package. The mounting bobbin of this package contains a 2.9 mm (0.114 inch) diameter hole (0.03 inch off center) designed
for mounting with a #4-40 screw.

1. A threaded hole in your mounting surface is necessary for mounting
the sensor package. The hole in the sensor package will
accommodate a #4-40 screw. A brass screw is recommended due
to the thermal contractions/expansions of the final assembly.

2. The threaded hole and surrounding surface should be cleaned with
a solvent such as Acetone followed by an Isopropyl Alcohol rinse.
Allow time for the solvents to evaporate before sensor mounting.

3. Apply a small amount of Apiezon
®
N grease to the threads of the
screw. To ensure good thermal contact between the sensor and
mounting surface, use an indium washer/preform or a thin layer of Apiezon
®
N grease between the mounting surface and
the sensor package. NOTE: An overabundance of grease will increase the thermal barrier. Keep the thickness to 0.05 mm
or less.

4. Insert screw through sensor mounting bobbin and tighten screw firmly enough to hold sensor in place. Avoid over
tightening (torque of 3

5 in-oz [0.02

0.035 N-M] should be sufficient).

NOTE: The standard CX-10XX-CU package with Formvar insulated wire is designed for use up to 325 K (52 °C).
The CX-10XX-CU-HT package with Polyimide insulated wire is designed for use up to 420 K (147 °C).

LEAD ATTACHMENT
The SD sensor has been attached to the mounting bobbin and encapsulated in Stycast
®
epoxy. The 0.91 meter (36 inch)
Polyvinal Formal (Formvar) insulated sensor leads are 36 AWG, phosphor bronze wire which are thermally anchored to the
bobbin. Teflon
®
tubing is used as a strain relief to reinforce the leads at the bobbin assembly. Standard lead configuration for
the CU is a four lead device [Red (I-), Green (V-), Black or Dark Blue (V+), Clear (I+)].

CU Package - Four-lead measurement scheme
The current is confined to one pair of current leads with the sensor voltage measured across the
voltage leads (see figure).

Thirty-six inches of lead wire is attached during the production process. If additional connection
wire is required, use the following instructions.

1. Prepare the sensor leads with a RMA (rosin mildly active) soldering flux, tin them with a
minimal amount of 60% Pb 40% Sn solder. Use a low wattage soldering iron that will not
exceed 200 °C. Clean off residual flux with rosin residue remover.

2. Strip the insulation from the connecting wires by delicately scraping with a razor blade, fine sand paper, or steel wool.
(Phosphor-bronze or Manganin wire, in sizes 32 or 36 AWG, is commonly used as the connecting lead wire. These wires
have low thermal conductivity which help minimize the heat flow through the leads. Typical wire insulation is Formvar
or Polyimide (ML). Formvar insulation has better mechanical properties such as abrasion resistance and flexibility.
Polyimide insulation has better resistance to chemical solvents and burnout.) Follow the same procedure in step 1 for
preparing connecting wires.

3. CU package - Identify lead polarities and apply the soldering iron above the joint area until the solders melt, then remove
the iron immediately. Leave enough slack to allow for the thermal contractions that occur during cooling which could
fracture a solder joint or lead. Insulating the soldering joint is recommended to prevent shorts. Use heat shrink tubing.

NOTE: The standard CX-10XX-CU package with Formvar insulated wire is designed for use up to 325 K (52 °C).
The CX-10XX-CU-HT package with Polyimide insulated wire is designed for use up to 420 K (147 °C).
4.3 mm thick
2.9 mm diameter,
0.8 mm off center
8 mm
diameter
Leads: 914 mm (36 inches), 36 AWG
Mass: 1.1 gram (excluding leads)


HEAT SINKING/THERMAL ANCHORING
Depending on the application, sufficient heat sinking of the leads may already exist in the bobbin. Use the following procedure
if additional heat sinking is recommended.

For additional heat sinking/thermal anchoring:
1. Connecting wires should be thermally anchored at several temperatures between room temperature and cryogenic
temperatures to guarantee that heat is not being conducted through the leads to the sensing element.

2. A simple thermal anchor can be made by winding the wires around a copper post, bobbin, or other thermal mass. A
minimum of five wraps around the thermal mass should provide sufficient thermal anchoring. However, if space permits,
additional wraps are recommended for good measure. To maintain good electrical isolation over many thermal cycles, it is
good practice to first varnish a single layer of cigarette paper to the anchored area then wrap the wire around the paper
and bond in place with a thin layer of IMI 7031 Varnish. Formvar wiring insulation has a tendency to craze with the
application of IMI varnish. If used, the wires cannot be disturbed until the varnish is cured and all solvents have
evaporated (typically 12

24 hours).


CRYOGENIC ACCESSORIES Recommended for proper installation and use of CX-10XX-CU sensors:
Apiezon
®
Type N and H Grease. P/N GAN-25 and GAH-25 25 g tube. Low viscosity, easy to use, solidifies at cryogenic
temperatures, excellent lubricant. Difference is melting point: Type N is 316 K, Type H is 523 K.
Heat Sink Bobbins. P/N HSB-40 Large, HSB-8 Small. Gold-plated copper bobbins. Large bobbin holds up to 40 wires, small
bobbin holds up to 8 wires, depending on wire gauge and number of turns.
High-Temperature Solder. P/N SLT-10 3 meters (10 feet). Greater lead content (90% Pb 10% Sn) for soldering in
applications up to 500 K.
Indium Foil/Solder. P/N IF-5 for 5 foil sheets (2" square × 0.005" thick), ID-10-31/ID-10-56 for 10 disks, 0.31" or 0.56"
diameter × 0.005" thick respectively. Indium is 99.99% pure, exceptional pressure seal, extremely malleable.
Ostalloy
®
158 Solder. P/N SOSY-16 16 oz. Reusable eutectic alloy with sharply defined melting point of 343.16 K (70 °C).
Stycast
®
Epoxy 2850FT, Catalyst 9. P/N ES-2-20 20 packets, 2 g each. Permanent attachment, excellent low temperature
properties, poor electrical conductor, low cure shrinkage. [Requires Hazardous shipping.]
VGE-7031 Varnish. P/N VGE-7031 0.5 liter (1 pint) can. Nonpermanent attachment, excellent thermal conductor, easy to
apply and remove. [Requires Hazardous shipping.]
Instruments: Lake Shore sells a complete line of instrumentation used with your sensor, such as: Current Sources,
Temperature Controllers, Monitors and Thermometers, Temperature Scanners and Transmitters.
Wire. Lake Shore offers numerous types of wires for various applications, including phosphor-bronze wires: Single Strand,
Duo-Twist, Quad-Twist, and Quad-Lead, Nichrome heater wire, non-magnetic Manganin wire, and more.
Cable. Lake Shore offers ultra-miniature coaxial cable (Type C, SC, and SS), semi-rigid coaxial cable (Type SR), and a robust
4-wire CryoCable (Type CYRC).

For complete product description and detailed specifications on the above accessories and instruments, consult the Lake
Shore Temperature Measurement and Control Catalog, call at (614) 891-2243, E-mail at sales@lakeshore.com, or visit our
website at www.lakeshore.com.



















Form Number F015-00-00 Revision C ©2000 & 2006 Lake Shore Cryotronics, Inc. 8 November 2006