Sunpower Inc. CryoTel
MT Operating Instructions version 4
12
Indium, Apiezon grease, or similar thermal grease between the sensor and the object to insure
proper thermal conduction.
Laboratory testing can be accomplished with a test cap arrangement similar to the one shown in
Fig 9. The test cap consists of a copper disk, two resistors, two through holes with M3
clearance for connection to copper tip, and two M3 holes for attachment of sensors to the test
cap. Calculate the heat load (power in Watts = current x voltage) by providing a known voltage
and current across the resistors on the test cap. Mount the control sensor using one of the M3
mounting holes on the test cap. If using a second sensor, mount it to the test cap for
independent temperature measurement. Apply an appropriate thermal grease to the bottom face
of the test cap in order to maximize conduction. Mount the test cap to the cold tip using the M3
threaded holes on the cold tip.
Figure 9: Test Cap Assembly
When the cold tip is contained in a vacuum vessel, use feedthroughs to connect the wiring
harness to the sensor wires. Use at least four conductors connecting the feedthrough to the
control temperature sensor. Use additional feedthroughs if employing a test cap or other
sensors inside the cryostat. All wires inside the cryostat should be as small as possible in order
to minimize parasitic loading on the cooler. The wires of the sensor and wiring harness are
color coded to help insure proper connection. Table 1 shows the proper connection of the
wires. Figure 10 and Table 2 describe proper connections of the wiring harness to the CryoTel
Controller.
Temperature
sensors
M4 Mounting
screws
Resistors
(heat load)
