A subject rife with errors, no matter how you look at it.

There’s a classic pair of books on temperature measurement that are hopelessly out of print. We are fortunate to have both in our little library. They are:

1. “Temperature Measurement in Engineering“, Volume I, by H.D Baker, E.A. Ryder and N.H. Ryder, John Wiley & Sons, Inc. New York and Chapman & Hall, Limited, London (Copyright 1953) Library of Congress Catalog Card Number 53-11565, and

2. “Temperature Measurement in Engineering“, Volume II, by H.D Baker, E.A. Ryder and N.H. Ryder, John Wiley & Sons, Inc. New York and London (Copyright 1961) Library of Congress Catalog Card Number 53-11565. [Click for the rest…]

 

Online — EarthTemp is a network to stimulate new international collaboration in measuring and understanding the surface temperatures of Earth. This will involve experts specialising in different types of measurement of surface temperature, who do not usually meet.

Their motivation is the need for better understanding of in situ measurements and satellite observations to quantify surface temperature as it changes from day to day, month to month.

Knowing about surface temperature variations matters because these affect ecosystems and human life, and the interactions of the surface and the atmosphere. (for more details, see motivations and objectives and scientific context – http://www.geos.ed.ac.uk/research/earthtemp/objectives.html and http://www.geos.ed.ac.uk/research/earthtemp/context.html).

The network is organised around three themes over three years.

In the first year (2012), they focused on Taking the temperature of the Earth: Temperature Variability and Change across all Domains of Earth’s Surfacehttp://www.geos.ed.ac.uk/research/earthtemp/themes/1_in_situ_satellite.

This is an inclusive question, designed to bring together research communities and develop a full picture of common research needs and aspirations.

The second year (2013) discusses Characterising surface temperatures in data-sparse and extreme regions (with an Arctic focus – http://www.geos.ed.ac.uk/research/earthtemp/themes/2_data-sparse).

EarthTemp People

Management group

Chris Merchant (Principal Investigator)
Dr. Chris Merchant is Reader in Earth Observation in the School of GeoSciences (University of Edinburgh). His principal expertise is use of thermal and reflectance imagery from satellites for observing surface temperature for climate applications, with interests also in lakes, aerosols, clouds, air-­sea fluxes and the radiation budget.

John Remedios (Co-Principal Investigator)
Prof. John Remedios is Professor of Earth Observation Science (EOS) in the Space Research Centre (University of Leicester). His research interests include surface temperatures and atmospheric correction; climate trends; measurements, retrievals and exploitation of tropospheric pollution and stratospheric composition; and validation and calibration of satellite instrument data.

Nick Rayner (Co-Principal Investigator)
Dr. Nick Rayner is a scientist at the Hadley Center (Met Office) where she leads the analysis of marine climate observations. Her expertise includes sea surface temperature, marine air temperature and sea ice observations, and the the statistical reconstructions of historical climate data.

Stephan Matthiesen (Project manager)
Dr. Stephan Matthiesen is a physicist and works as project manager and researcher at the School of GeoSciences (University of Edinburgh). He is also a freelance translator and editor of scientific texts.

Steering group

Jacob L. Høyer, Danish Meteorological Institute (DMI)
Phil Jones, University of East Anglia (UEA)
Folke Olesen, Karslsruhe Institute of Technology (KIT)
Hervé Roquet, Centre de Météorologie Spatiale, MeteoFrance
José Sobrino, University of Valencia
Peter Thorne, National Oceanic and Atmospheric Administration (NOAA)

Website support: Science and Engineering at The University of Edinburgh

Website: http://earthtemp.org/

News Feed: http://www.google.com/reader/public/atom/user/15733979554046153349/state/com.google/broadcast

And their really big advantages

At the risk of being insensitive by saying this sounds like a ‘Duh” moment let’s not. Let’s explore just what it means and why it is significant, especially in the case of temperature sensors.

The fact is, noncontact temperatures sensors, and similar noncontact sensors for size and shape are so-called because they measure a certain property by not contacting the object itself. Aside from the obvious side benefits of not causing any changes to the object being measured, noncontact temperature sensors have some significant benefits and accompanying advantages over contact temperature sensors.

As an aside, for just a moment realize that both contact and noncontact temperature sensors do not exactly measure anything, their indication of a temperature value is inferred from the combination of several factors.

In the case of contact temperature sensors, some analog, physical property of the sensor changes due to the sensor being in contact with the object of measurement. For example, a liquid-in-glass thermometer has the length of a thin column of colored liquid alongside a temperature scale changes as the sensor and object remain in contact.

The change is not immediate and the two must remain in contact for a sufficiently long period of time to say that the column length has stopped changing and the liquid column is said to be “in equilibrium” with the temperature of the object being measured. That is, to say, they are at the same temperature because there is no heat flow between them, or it is so small as to be neglected.

The length of the liquid column has been previously calibrated to the scale on its side to read in commonly used units of temperature.

This example points out the key factors in inferring the temperature of an object by a contact sensor: (1) they must be in contact long enough for the two to have (2) no heat flow between them, or be in thermal equilibrium with each other.

A noncontact temperature sensor, on the other hand needs no contact, but other factors enter into the inference of the temperature of the object for the sensor’s response to the object.

The most common type of noncontact temperature sensor is a single waveband radiation thermometer, or “IR thermometer”. It is basically a radiation receiver, or radiometer, that has been calibrated in terms of the temperature of a reference source of thermal radiation, most often a Blackbody simulator.

These are optical devices that use either or both mirrors or lenses to collect thermal radiation from a designed optical field of view and focus that radiation onto a sensing element or transducer. The transducer converts the thermal energy of the radiation received from an object into a physical response, either a small electrical signal or something else; electrical signals are most common.

If the object is a reference blackbody source that completely fills the optical field of view of the sensor, one can calibrate its electrical output versus the temperature of the blackbody and thus generate a calibration response for it.

In use, if one aims the noncontact sensor at an object that fills its optical field of view, its electrical response is an indication of the object’s temperature, not necessarily a complete or accurate measurement. Some additional factors need to be considered, such as the “non-blackbodyness” of the objects, whether there are effects from any of the intervening media that could attenuate or possibly enhance the amount of radiation received by the sensor.

It sounds complicated, and in truth, doing it from first principles, it is. However, this technology was discovered more than 100 years ago.The technology is very mature and has evolved into an engineering discipline rather than a research program.

The fact is: noncontact temperature sensors exist in a wide range of devices with many capabilities. They have, as promised above, some significant advantages over contact sensors.

First of all, they do not have to be, and in fact could be seriously damaged, if they reached the temperature of the object being measured, especially if it was very hot.

At temperatures above the melting point of most thermocouples and other high temperature sensing products, say above about 1700 °C (3092 °F), there are not very many ways to measure temperature at all. So, noncontact temperature sensors have a real advantage at the hot end of the temperature scale.

Since they do not have to be in thermal equilibrium, with the object being measured, that means there is no inherent time delay in getting a temperature measurement with a non-contact sensor.

The only time limit lies in the sensor’s own time response properties and that of the electronics to with they are very often connected. Sub-second temperature measurements are not only possible, they are usually very common.

Sub-millisecond response times, however, are less common and not found among the garden variety IR Thermometers one can buy for less than about $1000 USD!

SUMMARY:

1. Noncontact temperature sensors can measure very high temperatures with relative ease and survive…most of the time.

2. Noncontact temperature sensors can measure very quickly, often far more quickly than contact temperature sensors.

3. Noncontact temperature sensors can measure the surface temperature of solids and liquids often with better accuracy (and faster) than contact temperature sensors… (a subject to be examined in a later article.)

Temperature Calibration & Metrology Web Seminar Archives

Calibration

Fluke Calibration’s Focus on Basics – RTDs – Digital & IR (Infrared Radiation) Thermometers Online –  Fluke Calibration’s free online web seminars cover a wide range of calibration and temperature topics. More are scheduled monthly. To learn about upcoming events, check their web seminar page, or sign up for their e-news bulletins today. If you […]

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Data on Temperatures- Weather & Climate

Climate

  >>Temperature Data<< Temperature Data – NODC – NOAA www.nodc.noaa.gov › Access Data? by A Allegra – 2010 May 24, 2012 – Resources. temperature data title image. NODC’s most complete global temperature datasets are contained in: World Ocean Atlas/Database:. NODC’s most complete global temperature datasets are contained in: World Ocean Atlas/Database: Quality Controlled Data Online […]

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