There are many specialized glossaries that cover the terms describing the unique details about temperature and moisture sensors and their uses and this page represents an attempt to index most of them in one place.







Many online articles about radiation thermometry and its uses (infrared thermometers, radiation pyrometers) exist including technology articles, PowerPoint slide presentations and .pdf downloads, but they seem to be vanishing as more and more “big businesses” take over these specialized sensors.But few are aimed at being useful glossaries or definition of terms.

There are some exceptions and some well-crafted pieces that have been online for a while and can be found in semi-hidden corners of the Web.

Thermal Radiation Thermometers: temperature_measurement_radiation_thermometers

Thermal Imaging:  (Glossary of Basic Thermography Terms) .

Clearly this is a work in progress, and it may be expanded in time. Priority will be according to the response it garners.


Industrial temperature measurement | Basics and practice

Free Download From ABB

(Extract From the Introduction)

With this Handbook for industrial temperature measurements we are attempting to provide the technician with solutions to his wide variety of responsibilities. At the same time, it provides for those new to the field, insight into the basics of the most important measurement principles and their application limits in a clear and descriptive manner.

The basic themes include material science and measurement technology, applications, signal processing and fieldbus communication.

A practice oriented selection of appropriate temperature sensor designs for the process field is presented as well as therequired communication capability of the meter locations.

The factory at Alzenau, Germany, a part of ABB, is the Global Center of Competencefor Temperature, with numerous local experts on hand in the most important industrialsectors, is responsible for activities worldwide in this sector.

125 years of temperature measurement technology equates to experience and competence. At the same time, it forms an important basis for continued innovation.

In close cooperation with our customers and users, our application engineers create conceptsto meet the measurement requirements.

Our Sector-Teams support the customer, planner and user in the preparation of professional solutions.

Free download available online at:

Author Team:
Karl Ehinger, Dieter Flach, Lothar Gellrich, Eberhard Horlebein, Dr. Ralf Huck, Henning Ilgner, Thomas Kayser, Harald Müller, Helga Schädlich, Andreas Schüssler, Ulrich Staab,

ABB Automation Products GmbH

Many thanks to the publishing group at ControlEngineering-Europe for alerting us to this new online resource (

Mercury Thermometer Alternatives by NIST

Promoting alternatives

no mercuryOnline —  The USA’s National Institute for Science & Technology (NIST) is not only  the nation’s National Metrology Institute (NMI), it also serves additional roles, including cooperating with other government agencies to safeguard people from harm due to sensors or practices that could be hazardous.

About 20 years ago the use of mercury-filled sensors, such as barometers, hygrometers and liquid-in-glass thermometers were recognized as sources of long-term hazards to man and nearly all animals.

The Federal Drug Administration (FDA) and Environmental Protection Agency (EPA) began efforts to ban the use of mercury in such devices and NIST has been in the forefront of the effort, along with volunteer organizations like ASTM International.

NIST has published a series of webpages that describe the issues related to mercury filled thermometers and considered several alternatives, some of which, in this Editor’s opinion are long overdue.

The rest of this article is copied from the December 22, 2016 NIST webpage: that begins the NIST series of information pages to help users understand some of the alternatives to mercury-filled  Liquid-in-Glass thermometers.

In effect these new temperature sensor alternatives bring many testing and measuring practices into the modern world of both sensor and display technologies, providing durability, precision and traceability along with digital options, in many cases.

Mercury-filled thermometers have historically served numerous industries as reliable temperature standards. Increased regulation and the high cost of cleaning up mercury spills have encouraged the use of alternative types of thermometers.

To support the use of alternative thermometers, the NIST Temperature and Humidity Group provides guidance documents, training, and technical consultation to other government agencies and standards-developing organizations.

Replacement of mercury thermometers with suitable alternatives will reduce releases of mercury into the environment and will reduce costs incurred to clean up mercury spills.

Historically, healthcare and regulated testing laboratories have relied greatly on NIST-calibrated mercury-in-glass thermometers as stable reference standards of temperature.

The use of mercury thermometers has been virtually eliminated in routine hospital use, but a wide variety of regulations and test methods continue to specify mercury thermometers.

Mercury thermometers have several intrinsic advantages:

  • they are stable for long periods,
  • failure is usually visually apparent, and
  • they require little training or maintenance.


However, mercury is a powerful neurotoxin, and the cost of cleaning a mercury spill in industry is many thousands of dollars. Furthermore, many states restrict the sale of mercury thermometers.

In 2008, the NIST Temperature and Humidity Group worked with several organizations to reduce or eliminate the use of mercury thermometers.

Environmental Protection Agency (EPA):  the EPA hosted meetings in the Spring of 2008 to discuss strategies to eliminate the use of mercury thermometers in EPA regulations and laboratories. NIST provided technical guidance documents, presentations, and technical advice as experts in temperature measurements.

Clinical Laboratory and Standards Institute (CLSI):  NIST Temperature and Humidity Group staff have worked with CLSI staff to update standards calling for the use of mercury-in-glass SRM thermometers, enabling laboratories to use other thermometer types with NIST traceability.

Centers for Disease Control and Prevention (CDC):  Control of temperature is critical to proper storage of vaccines, in order to preserve safety and efficacy. At CDC’s invitation, the NIST Temperature and Humidity Group gave a presentation at the May, 2008 “Vaccine University” that CDC sponsors. Over 60 participants learned how traceable temperature measurement and control can be achieved with modern electronic thermometers.

These activities build on support provided in 2007 to the Food and Drug Administration (steam processing of food) and ASTM committee D2 on petroleum.

In an environment of increased regulatory and economic pressures to discontinue the use of mercury thermometers, NIST has provided timely and critically important technical advice to other federal agencies and thermometer users, ensuring that important industrial and health-care temperature measurements are performed efficiently and accurately.

Major accomplishments:

  • Guidance document published on how to identify alternatives to mercury liquid-in-glass thermometers.
  • Technical support provided to other government agencies and to developers of documentary standards.


Links to other NIST webpages:


Selected Publications & Related Links


Questions about Mercury Thermometer Alternatives?

Temperature Measurement with your Computer

Windmill LogoOne of the best of our favorite resources on the Web is a software company on Manchester, England, Windmill Software. They have supplied free PC software for Test & Measurement to all who wish to download it from their website:,

Windmill has for many years also published a free monthly informative eNewsletter called Monitor newsletter (ISSN 1472-0221); archive and subscription available online at

At last look it was up to issue No, 224!

Here’s links to one of the extra specials they have done on the subject of temperature measurement


Measuring Temperature with a Computer

Temperature measurement is the most common application of data acquisition systems. You will need a device to measure the temperature – a temperature sensor. Thermocouples, resistance temperature devices (RTDs), thermistors, platinum resistance thermometers and infrared thermometers are all types of temperature sensor.

The most popular are thermocouples and RTDs. The sensors you choose depends on several things, such as as your expected maximum and minimum temperatures, cost, accuracy needed and your environmental conditions.

To get data from the temperature sensor into your PC you need a data acquisition interface with suitable software. The interface unit plugs into your computer, for example into the USB or Ethernet port.

You wire the sensor to the interface, install the software and the computer can now monitor temperatures.

Comparison of Thermocouples and RTDs

National Physical Laboratory Video Presentations on Temperature Measurements


New references for high temperature measurements

As a culmination of an eight-year research programme an international collaboration has developed robust reference fixed points, studied their sensitivity to impurities and external conditions and finally measured their melting transition temperature.

This talk describes how 100+ measurements made by nine different NMIs have been combined to assign low-uncertainty thermodynamic temperatures to the melting transition of Re-C, Pt-C and Co-C metal-carbon eutectics.

At the simplest level, these fixed-points will provide new temperature references for the calibration of pyrometers at temperatures above the freezing point of silver (1234.93 K) and will thus reduce the uncertainties associated with high temperature measurement compared to those achievable using the International Temperature Scale of 1990 (ITS-90).

The thermodynamic temperatures of these fixed-points have been determined through direct measurement of the radiance of a blackbody cavity surrounded by the fixed-point material from Planck’s law and hence the Boltzmann Constant. The evolving mise en pratique for the definition of the kelvin encourages the realisation and dissemination of thermodynamic temperature.

This may be directly – and the work described in this talk shows that filter radiometry is sufficiently mature for this, or it may be by providing fixed-points with reference thermodynamic temperatures that have associated uncertainties – and this talk will outline such temperatures.
Innovations in High Temperature Measurement

A 49 minute review of the present technical status of High Temperature measurement by one of the leaders in temperature Metrology at NPL in the UK.

Presented by Dr. Graham Machin, NPL (Recorded July 2011)

Recent and unfolding innovations in this area promise step change improvements throughout the measurement chain; from realisation of temperature above 1300 K in National Measurement Institutes, dissemination of the scale to calibration laboratories, down to the practice of industrial high temperature thermometry.


More details: Read more National Physical Laboratory Video Presentations on Temperature Measurements

The most accurate temperature measurements ever made. Probably.

NPL Lecture by Michael de Podesta

It is now 25 years since the establishment of the International Temperature Scale of 1990. The scale has been extremely successful in enabling accurate and consistent temperature measurement around the world.

However, it has become clear that the thermodynamic temperature estimates on which ITS-90 is based were in error, even at temperatures close to the triple point of water.

The discovery and elucidation of this error is largely due to the development of acoustic thermometry.

Over the last decade, the development of combined microwave and acoustic resonators for the measurement of the Boltzmann constant has improved the state-of-the-art significantly and resulted in advances in theory, fabrication, and experimental techniques.

After reviewing some of these advances, we present new data on T – T90 at twenty temperatures in the range from 118 K to 303 K.

The differences agree well with other recent estimates, but our low uncertainty reveals previously unseen detail. These measurements probably constitute the most accurate measurements of temperature ever achieved.



Recorded: 16 June 2015

Speaker: Michael de Podesta

Wake Frequency Calculator by TempSens Instrument

Plus two additional Calculators

Wake_Frequency_CalculatorAn online resource calculator for estimating the Wake Frequency of a thermowell in a flowing stream.

According to the website:

“TEMPSENS WAKE FREQUENCY CALCULATOR is easy to use and it also ensures that thermowell is designed within the dimensional limits of PTC19.3, 2010. This calculator establishes the practical design considerations for Thermowell installations in power and process piping, which also incorporates the latest theory in the areas of natural frequency, Strouhal frequency, in-line resonance and stress evaluation.”

The program is “FREE” and can be distributed to other users, this was developed for Tempsens internal use and then we have now a lot of customers requesting for a copy of this program. Please give your inputs for improvement in the program.


The same web page provides a Temperature Calculator to convert the Emf (mV)/Ohms generated by thermocouple & RTD to the temperature or vice versa as well as a SPRT Calculator to provide the ITS-90 coefficients for the set of resistance readings provided on the fixed point cell.

New ASTM Standard For Digital Thermometers

ASTM E2877, Guide for Digital Contact Thermometers

Digital Display with Temperature 27 Deg. C by palomaironique
Image Courtesy of

W. Conshohocken PA, USA — A new ASTM International standard provides a variety of recommendations for the manufacture and selection of digital thermometers. ASTM E2877, Guide for Digital Contact Thermometers, was developed by Subcommittee E20.09 on Digital Contact Thermometers, part of ASTM International Committee E20 on Temperature Measurement.

Included in ASTM E2877 is a set of accuracy classes for digital thermometers. These classes pertain to the temperature interval from -200 °C through 500 °C, an interval important for many thermometry applications.

In order to qualify for a specific accuracy class, a thermometer must measure correctly to within a specified value over this interval or the subinterval in which the thermometer is capable of making measurements.

Digital thermometers that are used for measuring temperature in many laboratories and industrial applications are being increasingly seen as environmentally safe alternatives to mercury-in-glass thermometers, particularly since the U.S. Environmental Protection Agency’s efforts to phase out mercury thermometers are under way.

According to Christopher W. Meyer, a physicist at the National Institute of Standards and Technology, and an E20 member, the petroleum industry and others have used mercury thermometers for decades.

“These industries wish to convert to digital thermometers but until now there has been no ASTM standard for them,” says Meyer. “Also, there has been no set of defined accuracy classes that could help specify the type of thermometer needed for a given application. ASTM E2877 is necessary for instructing these industries in the basics of digital thermometers and for providing a standard that can be used in operation protocols.”

The new standard describes three types of sensors used in digital thermometers: platinum resistance sensors (PRTs or RTDs), thermistors and thermocouples (TCs).

“ASTM E2877 describes the various types of contact digital thermometers that are on the market and discusses the relative characteristics of each,” says Meyer. “It also defines a set of accuracy classes for digital thermometers that may be used to help specify the type of digital thermometer needed for an application. It will allow industries that have previously specified mercury thermometers in their protocols to use digital thermometers.”

All interested parties are invited to join in the standards developing activities of E20.09.

To purchase ASTM standards, visit and search by the standard designation, or contact ASTM Customer Relations (phone: 877-909-ASTM; ASTM International welcomes participation in the development of its standards. For more information on becoming an ASTM member, visit

For more news in this sector, visit or follow ASTM on Twitter @ASTMProductsRec.

ASTM Committee E20 Next Meeting: May 20-21, 2013, May Committee Week, Indianapolis, Ind.

Technical Contact: Christopher W. Meyer, National Institute of Standards and Technology, Gaithersburg, Md., Phone: 301-975-4825;

ASTM Staff Contact: Christine DeJong, Phone: 610-832-9736;

ASTM International, formerly known as the American Society for Testing and Materials (ASTM), is a globally recognized leader in the development and delivery of international voluntary consensus standards. Today, some 12,000 ASTM standards are used around the world to improve product quality, enhance safety, facilitate market access and trade, and build consumer confidence.

ASTM’s leadership in international standards development is driven by the contributions of its members: more than 30,000 of the world’s top technical experts and business professionals representing 150 countries. Working in an open and transparent process and using ASTM’s advanced electronic infrastructure, ASTM members deliver the test methods, specifications, guides, and practices that support industries and governments worldwide.
Learn more about ASTM International at

The Pros & Cons of RTDs & Thermocouples – By Jim Pinto

Jim Pinto One useful resource on RTD and Thermocouple sensors was found at Jim Pinto’s Writings section of his website, borrowed from the original article that he wrote for Instruments & Control Magazine in June 2000, at:

In the article Jim takes particular care to describe the likely errors that can occur with less-than-perfect cold junction correction in some electronic thermocouple instruments (i.e. signal conditioners, displays, controllers and transmitters)

He prefaces his remarks by saying:

Resistance temperature detectors and thermocouples can be used for some of the same measurements, but each has strengths and weaknesses that must be carefully matched to the application at hand.

The original version of this article was published in the leading USA magazine – Instruments & Control Systems, June 2000

(Click here for a copy from the I&CS website:

Jim Pinto is an extraordinary person who has been very active in the ISA – the International Society for Automation, where he is Fellow of the Society. He founded Action Instruments and since about 1998 has shared his thoughts and experiences with the world through various media including, since about 2000, his website,  and his YouTube Channel, online at:

His personal profile is available on at: (credit for Jim Pinto’s Picture belongs to that page) and on Linkedin at: where many images and video recordings of Jim may be viewed.

Using a 3-Wire RTD to Reduce Temperature Measurement Errors

Ensure High Accuracy in Your Critical Temperature Measurements

DataloggerCHESTERLAND OH, USA — To prevent inaccurate temperature measurements which can potentially cause disastrous inventory losses, CAS DataLoggers recommends using 3-wire RTDs to customers taking temperature measurements using RTD sensors.

These sensors are affordable and easily available for use with our wide inventory of temperature dataloggers, but some users are unaware of this more accurate option. With this in mind, Applications Specialists have put together this brief guide to show the need for 3-wire RTDs.

RTD sensors make simple resistance measurements, usually at about 100 ohms, which is a relatively low level of resistance. Therefore an RTD measurement error of 1 ohm or more is quite significant, for a regular RTD at room temperature, the resistance is 109.1 ohms, and even a 1-ohm error in that measurement will cause a temperature error of about 2.5 °C.

When using a 2-wire RTD, users may find that the resistance of the connections between the sensor and datalogger directly affects the temperature measurement, so this is easily avoided by using a 3-wire RTD, which enables the connected datalogger to compensate for the resistance of the circuit.

An example of this kind of measurement error occurs when connecting an RTD to a piece of 20 AWG (American Wire Gauge) copper hookup wire (solid or stranded), with electrical resistance* of about 1 ohm per 100 ft. of length.

In this case, using a 2-wire RTD with a 50-ft cable on it can result in a 2 ° to 2.5 °C systematic temperature error just due to the resistance of the wire.

So, especially with longer cable runs, users can avoid this significant error source by using a 3-wire RTD sensor along with a data logger that provides automatic compensation for these types of applications.

* Reference the electrical resistance of copper wire versus AWG size on the HyperPhysics website at: (NOTE:  HyperPhysics is a free online educational resource by Dr. Rod Nave at the Georgia State University in Atlanta GA, USA.  A CD/DVD version  is available for purchase at: Apps for iPhone and iPad are also available at small or moderate cost at Apple’s iTunes store.)

CAS DataLoggers products are used in a wide variety of applications in remote monitoring, in industrial process and manufacturing industries, for automotive and aerospace data collection, in pharmaceutical manufacturing and storage, and in geological and environmental monitoring—there are even units on the Space Shuttle and ISS (International Space Station)!

Sophisticated data acquisition and control systems are also available including high performance real-time systems for situations where traditional test systems or programmable controllers are not suitable.

These systems are used in data acquisition, test and control applications where microsecond precision is needed. Models are available with 8 to over 400 analog input channels, analog output channels, digital inputs and outputs, counters, RS-232, RS-485 CANbus and Profibus interfaces. CAS DataLoggers also provides configuration assistance, custom programming, custom system design and assembly, post-sales technical support, and repair and calibration services. Development capabilities include custom data acquisition and data logging systems, test and measurement systems, and portable data collection systems.

For more information on a wide range of temperature dataloggers from Accsense, T&D, Grant and more, or to find the ideal solution for your application-specific needs, contact a CAS Data Logger Applications Specialist at (800) 956-4437 or visit the website at

Contact Information:
CAS DataLoggers, Inc.
12628 Chillicothe Road
Chesterland, Ohio 44026

Tel: +1 (440) 729-2570 and, Toll-free: (800) 956-4437