World's first practical Johnson Noise Thermometer
developed by .......METROSOL
Metrosol in conjunction
with the National
Physical Laboratory (NPL) have developed the world's
first practical Johnson Noise Thermometer. So far we have
developed and patented the technique and instrument concept.
We have also produced a desktop proof of principle working
prototype and can make measurements in a normal laboratory
The initial phase of this work was part funded by Innovate
UK as a feasibility
study in their “Development of the Civil Nuclear
Supply Chain” competition.“ The outcome
of this feasibility study exceeded our expectations.
Johnson Noise Thermometry
Johnson noise thermometry (JNT) is a primary temperature
measurement technique based on the fundamental properties
of thermal fluctuations in conductors.
A Johnson noise thermometer never needs calibrating and
is insensitive to the condition of the sensor material,
so is ideally suited to long-term temperature measurements
in harsh environments, such as nuclear reactor coolant circuits,
nuclear waste management and storage.
Johnson noise (thermal noise, Johnson-Nyquist noise, white
noise) is the electronic noise generated by the thermal
agitation of the charge carriers (usually the electrons)
inside an electrical conductor, which happens regardless
of any applied voltage. The generic, statistical physical
derivation of this noise is called the fluctuation-dissipation
Johnson noise in an ideal resistor is white, meaning that
the power spectral density is constant throughout the frequency
spectrum (except at extremely high frequencies). As the
Johnson noise is the results of many independent charge
carrier movements, the central limit theorem states that
the resulting noise voltage will have a normal or Gaussian
The most important aspect of Johnson noise from our point
of view is that the power of the Johnson noise is directly
proportional to absolute temperature. There is no material
property or calibration requirement to derive the absolute
temperature, just electrical measurements. Therefore this
technique is not subject to sensor drift.
We are now seeking partners or investors to
take the project to the next stage, or work with you to
help you measure Johnson Noise on your project. Contact
Metrosol to register your interest.
THE METROSOL ETHOS .....
Our Ethos can simply be stated as “uncompromising”.
We believe that the difference between an adequate (or even
a good) product and a world-class product is in the fine
detail and at Metrosol we are unflinching in our search
for perfection. We employ a continuous improvement approach,
refining our designs and manufacturing processes in order
to ensure that our products always deliver the highest performance
and are of the highest quality.
Our approach is to look for innovative solutions to measurement
problems that provide tangible benefits to users of our
instruments. We collaborate with a number of partners (National
Measurement Institutions and commercial organisations) who
are acknowledged leaders in their field in the development
of our technology. The extensive range of skills we can
deploy allows Metrosol to take a product design from a market
requirement to a fully engineered instrument, ready for
Our aim is always to exceed our customers’
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