Precise temperature measurement is an integral part of many laboratory experiments and industrial processes, and becomes especially important for the technical demands of cryogenics. Quantum Technology can supply the equipment and expertise you need for your application, and will follow up with installation and servicing where required.

The cryogenic temperature sensors available from Quantum fall into four broad classes. Since different physics prevails in each class, and different physical quantities are measured, careful consideration must be given to select a sensor compatible with your requirements. The following general product descriptions and selection guide are designed to make your search easier.

Q07.1 Diode sensors:

The temperature dependence of the junction forward voltage, measured typically at 10 microamps, is invoked. Two types are available:

• Silicon
  • 1.4 K to 475 K
  • Interchangeable -- conform to standard calibration curves
• Gallium aluminum arsenide (GaAlAs)
  • 1.4 K to 325 K
  • Reliable in magnetic fields up to 5T

Q07.2 Resistive sensors:

These may be further subdivided according to the resistive material and hence the slope of the temperature dependence:

• Metals
  • positive temperature index
  • useable over a wide range
  • highly resistant to ionizing radiation
  • Types available:
    • Platinum
      • 30 K to 873 K
      • Interchangeable -- conform to DIN and IEC standards
    • Rhodium-iron
      • 1 K to 500 K
      • Good long term stability
    • Nickel-manganin
      • 4 K to 313 K, linear response
      • Strain gauge style
      • Low cost
• Semiconductors (negative temperature index):
  • Germanium
    • Choice of ranges between 0.05 K and 30 K
    • Interchangeable -- recognized as a Standard Thermometer
    • Good resistance to ionizing radiation
  • Carbon-glass
    • 1.4 K to 100 K
    • Excellent for use in magnetic fields to 19 T
    • Good resistance to ionizing radiation
  • Cernox
    • 0.3 K to 325 K
    • Excellent for use in magnetic fields to 19 T
    • Highly resistant to ionizing radiation
    • Various package options available
  • Ruthenium Oxide
    • 0.02 K to 100 K
    • Reliable in magnetic fields up to 5 T
    • Interchangeable -- conform to standard curves

Q07.3 Capacitive sensors:

Measurement capability is based on the temperature dependence of the dielectric constant of the ferroelectric used. They feature

• Excellent behaviour in magnetic fields
• Poor accuracy, making them useful only as control sensors

Types available:

• Multilayer ceramic -- 1 K to 290 K
• Strontium titanate -- 1 K to 60 K

Q07.4 Thermocouples:

The voltage developed at the junction between two metals depends on temperature. Thermocouples are know for

• Small size and measurement simplicity
• Low cost
• Fair accuracy
• Interchangeability (ASTM standard)
• Good resistance to ionizing radiation

The most popular types for cryogenic use are:

• Chromel-constantan (Type E) -- 3 K to 475 K
• Chromel-alumel (Type K) -- 3 K to 575 K
• Chromel-copper/iron -- 4 K to 300 K