Cryogenic sensors: Platinum cobalt resistance sensor

What are cryogenic sensors?

Cryogenic sensors are a type of RTD (Resistance Temperature Detector) specifically designed for extremely low (cryogenic) temperatures. Our platinum cobalt cryogenic (cryo) sensors provide reliable and accurate performance at temperatures below 73K(-200°C), even going down as low as 1.5K (-271°C). These are temperature ranges far beyond the scope of standard cryogenic platinum sensors.

Cryogenic sensors can, for example, be found in aerospace applications, medical industries, liquid hydrogen tanks and superconducting devices.

Introducing the CERACOIL,

For this type of cryogenic thermometry, Kamet has chosen to work with our long-standing partner, Okazaki. Their platinum cobalt sensor, CERACOIL, combines excellent cryogenic properties with the exceptional quality standard that Okazaki is renowned for.

Okazaki has been involved in the production of sensors for space equipment mounted on Japanese H-IIA/H-IIB spacecrafts. Furthermore Okazaki is authorized and registered on the European preferred part list (EPPL) for the European Space Agency (ESA).

The patented CERACOIL was developed by Okazaki and incorporates technology developed for various aerospace applications where accuracy in extreme conditions is essential. As such, CERACOIL sensors can be relied on for exceptional quality and high precision readings in most cryogenic applications.

The platinum cobalt sensor, CERACOIL, is available in two resistances, Pt100 and Pt1000.

Physical properties

Okazaki’s platinum cobalt cryogenic sensor offers a number of important advantages:

  • the tightly wound platinum resistance wires make these sensors suited to environments with high levels of vibration
  • excellent resistance value changes, even below 4K(-269°C).
  • superior repeatability
  • temperature measurement is feasible at exceptionally low temperatures (as low as 1.5K (-271°C))

The product specifications for the CERACOIL are as follows:

Nominal resistancePtCo 100Ω / 1000Ω at 0°C
Measurement temperature range1.5 K to 373 K (-271°C to 990°C)
Tolerance ±0.5 K at 4 K to 40 K / ±1 K at 273.15 K
Reproducibility*±20 mK (at 10 K) / ±10 mK (at 20 K) / ±33 mK (at 273.15 K)
Measuring current1 mA
Element dimensionsØ1.4 x 12 mm
Length (L)Pt100 25 mm / Pt1000 50 mm
Outside diameter (D)Pt100 2.0 mm / Pt1000 3.5 mm
*Reproducibility is the change amount from the initial value after 1000 heat cycles between 77 K and 300 K (-195°C to 26°C).

PtCo 100Ω Temperature – Resistance Table

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PtCo 1000Ω Temperature – Resistance Table

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A note about silicon diodes

Sometimes silicon diodes are used for temperature measurement in cryogenic applications. While these sensors have some advantages in terms of interchangeability and price, they also have distinct disadvantages. In comparison to platinum cobalt sensors, silicone diodes are:

  • significantly less accurate
  • strongly influenced by magnetic fields at temperatures below 40K(-233°C)
  • tend to self-heat due to their relatively high power dissipation

In conclusion, where high accuracy is required, such as is the case for components in critical systems, then the cost of sensor failure can be considered higher than the cost of investing in a high quality cryogenic sensor, such as the CERACOIL. 

Industrial applications of cryogenic sensors

Cryogenic sensors play a critical safety role in various applications, including medical and pharmaceutical industries. fusion reactors and maglev trains. We take a closer look at a few other applications below.

– Particle accelerators

Cryogenic sensors are a critical component in supercolliders (particle accelerators) where superconductivity has become a key technology. Cryogenics is primarily used to cool the superconducting components of particle accelerators. These cryogenic systems operate at temperatures from 4.2 K (-268°C) in supercritical, down to 2 K (-271°C) in superfluid. 

Superconducting particle accelerators represent a field of industry that is set to expand with new conductors planned for Europe, Asia and America. It is therefore essential that cryogenic sensors continue to be developed and improved in order to meet these future demands.

This is another reason why we have chosen to stock Okazaki products, as they are a partner valued for their cutting edge research and development.

– Satellites and space telescopes

(Research) satellites and space telescopes increasingly include cryogenic technology in the form of cryocoolers to ensure their operation at optimal performance. As such, cryogenic sensors have become an important part of the ancillary instrumentation in these structures. 

– Cryogenic storage of gases

Cryogenic storage (such as of liquid hydrogen) is used as a means to efficiently store large quantities of gas. By cooling the gas to cryogenic temperatures, it becomes liquid. Hydrogen is, for example, 851 times more compact when in liquid form. However, cryogenic storage and transportation of gases can be dangerous, and temperature control is a critical safety measure in ensuring that the required low temperatures are maintained. Cryogenic sensors placed inside the gas storage tank play an important role in this control and monitoring process.

Would you like to know more?

Okazaki is an industry leading company in the temperature world. In terms of quality, the aerospace factory producing these sensors has ISO9001, ISO14001 and JIS Q 9100 certifications.

Get in contact

Do you have questions or want advice on your particular cryogenic application? Reach out to our team of experts and they will be happy to assist and advise you further.

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