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: https://library.e.abb.com/public/6bfb8fc893ac4d0da0a806ce8cd73996/03_TEMP_EN_E.pdf

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 (http://www.controlengeurope.com/article/140944/Handbook-aims-to-simplify-industrial-temperature-measurement.aspx)

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: https://www.nist.gov/pml/sensor-science/thermodynamic-metrology/mercury-thermometer-alternatives-promoting-alternatives 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: http://www.windmill.co.uk,

Windmill has for many years also published a free monthly informative eNewsletter called Monitor newsletter (ISSN 1472-0221); archive and subscription available online at http://www.windmill.co.uk/newsletter.html.

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

(Excerpt)

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.

Source: http://www.npl.co.uk/science-lectures/high-temperature-measurement

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.

Source: http://www.npl.co.uk/science-lectures/the-most-accurate-temperature-measurements-ever-made-probably

Video: https://www.youtube.com/watch?v=Irr8fOLtiWc

Recorded: 16 June 2015

Speaker: Michael de Podesta

Thermocouple Junctions Are Not Voltage Sources!

by R. P. Reed, Ph.D, PEret

NOTE: The following is a brief overview of a special article written and published here by a noted authority on thermocouples. Dr. Ray P. Reed. Dr. Reed is a retired researcher from Sandia Laboratories in New Mexico, USA.

He is a semi-retired, yet still a contributing member of the ASTM International Committee E20 on Temperature Measurement. He has written and presented many professional and peer-reviewed articles on temperature sensors, notably thermocouples in his long career.

His list of publications is on another page on this website, http://www.temperatures.com/resources/temprefs/publications-presentations-of-r-p-reed/.

This new article from R.P. Reed is published with his permission and is in downloadable format.

It is in Adobe PDF format and its size is about 310 kb.

Here’s a sample of the initial paragraph of the article:

“Thermocouples, based on the Seebeck effect, remain the simplest, most widely used, electrical sensor of temperature. Thermocouples consist only of thermoelectrically dissimilar conductor legs connected at junctions. The Seebeck emf occurs only in the legs. Therefore, commonplace calibration and thermometry errors relate to degraded thermoelements, not to junctions. A yet commonplace implicit Junction-Source Model incorrectly asserts that Seebeck emf occurs only in junctions. That erroneous concept hides problems that are commonplace in consequential thermometry.”

Link to a full Introduction to the article and the download link Link: http://www.temperatures.com/thermocouple junctions are not voltage sources!/

TI Temperature Measurement Videos

TI, or Texas Instruments, is one of the world’s most prolific and largest makers of temperature sensors. They make all kinds but their sensors are mostly in the form of Integrated Circuit semiconductors.

TI also does an exceptional job in educating users how their devices work and how they can be interfaced and incorporated in measurement systems. Especially useful are the videos showing how some of their other integrated circuit modules can be used with external temperature sensors, like Thermocouples, RTDs and Thermistors.

Here’s an example of an interesting one:

Developed through TI’s expertise in MEMS technology, the TMP006 is the first of a new class of ultra-small, low power, and low cost passive infrared temperature sensors. It has 90% lower power consumption and is more than 95% smaller than existing solutions, making contactless temperature measurement possible in completely new markets and applications.

Check out their Video Channel on YouTube, especially the long list of videos already published about “Temperature Measurement”. It very straightforward; just go to: https://www.youtube.com/user/texasinstruments/search?query=%22temperature+measurement%22

Precision & Accuracy in Measuring Surface Temperatures

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. Read more Precision & Accuracy in Measuring Surface Temperatures

Why Noncontact Sensors are So Named

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

Fluke Calibration’s Focus on Basics – RTDs – Digital & IR (Infrared Radiation) Thermometers

Calibration and Metrology Web Seminar Series

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 have missed out on one of their live web seminar events, you can view the recordings in their web seminar archives. Here’s a list of current ones along with links to them (as of 1 August 2013). They are mostly in English, but several are also in Spanish.

Introduction to Temperature Measurement and Calibration

Techniques and Common Methods of Temperature Calibration

How Do You Know that Your Digital Thermometer is Accurate? »

How to Create a Temperature Measurement Uncertainty Budget »

Replacing Mercury Thermometers  Once and for All »

Kelvin and SI Units »

Redefinition of SI Units (Kelvin, Kilogram,  Ampere & Mole) »

How to Calibrate an RTD or Platinum Resistance Thermometer »

Cómo Calibrar un RTD »

How to Calibrate an RTD Using a Dryblock Calibrator »

Cómo Calibrar un RTD Usando un Calibrador de Bloque Seco »

Overcoming Drift: A Complete Guide to Maintaining Your PRTs »

Annealing an RTD: Why, When and How »

How to Maximize SPRT Measurement Performance »

Understanding Uncertainties Associated with Dryblock Calibrators »

How to Calibrate an IR Thermometer »

Como Calibrar Termómetros Infrarrojos »

Infrared Temperature Calibration 101 »

Advancements in Digital Thermometry Bridge Technology »

What is 0.06 PPM, Can Calibrate itself, and  costs much less that a bridge? »

Best Practices in Maintaining Temperature Calibration Equipment »

Making Laboratory Accreditation Work for You »