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?

WMO World Weather & Climate Extremes Archive

About The Archive

Screen Shot 2017-09-14 WMO Archive PageOnline —  In 2006, the World Meteorological Organization (WMO) Commission for Climatology (CCl) WMO OPAG 2 group unanimously agreed to the creation of a world archive for verifying, certifying and storing world weather extremes.

They agreed that a set of procedures should be established such that existing record extremes are verified and made available to the general public and that future weather record extremes are verified and certified.

They agreed that future weather extremes would be evaluated by a committee consisting of the WMO CCl Rapporteur for Climate Extremes, the chair of the OPAG 2 group, the chair of the overarching CC1 group, a regional authority, and as necessary an authority associated with the specific type of record (temperature, pressure, hail, tornado, tropical cyclone, etc.).

The committee would recommend a finding to the Rapporteur. The Rapporteur for Climate Extremes would have final authority and responsibility for certifying the record.

All accepted and verified record extremes (with corresponding metadata) are to given on this website.

Inquiries for consideration of new world/regional weather records should be made to the Rapporteur for Climate Extremes: Randy Cerveny (cerveny@asu.edu)

 

Archive TaWorld Meteorological Organization's World Weather & Climate Extremes Archivebles include:

Temperature: Highest & Lowest Temperature

Pressure: Highest Sea Level Air Pressure Below 750 m, Highest Sea Level Air Pressure Above 750 m, and Lowest Sea Level Air Pressure (excluding tornadoes).

Rainfall: Greatest 1-Min Rainfall, Greatest 60-Min Rainfall, Greatest 12-Hr Rainfall, Greatest 24-Hr Rainfall, Greatest 48-Hr Rainfall, Greatest 72-Hr Rainfall, Greatest 96-Hr Rainfall, and Greatest 12-Mo Rainfall.

Hail: Heaviest Hailstone

Aridity: Longest Dry Period

Wind: Maximum Gust, Maximum Gust for Tropical Cyclone

Lightning :Longest Distance Lightning Flash, Longest Duration Lightning Flash

Weather-Related Mortality:  Highest Mortality: Lightning, Highest Mortality: Lightning (single stroke), Highest Mortality: Tropical Cyclone, Highest Mortality: Tornado, Highest Mortality: Hailstorm

Hemispheric Weather & Climate Extremes

Continental Weather & Climate Extremes: Based on World Meteorological Organization Defined Regions

World Tornado Records

World Tropical Cyclone Records

World Meteorological-Related Phenomena Records

Open MapViewer

and,

Latest News

Members of the inaugural WMOCCL OPAG2 committee for the World:

  • Craig Donlon (United Kingdom)
  • Jay Lawrimore (United States)
  • Rainer Hollmann (Germany)
  • Thomas C. Peterson (United States)
  • Wan Azli Wan Hassan (Malaysia)
  • Xiaolan Wang (Canada)
  • Zuqiang Zhang (China)

 

Current managers of the WMO Weather and Climate Extremes Archive are:
Dr. Randy Cerveny, School of Geographical Sciences, Arizona State University
Bohumil Svoma, School of Geographical Sciences, Arizona State University

Visit the Archive online at: https://wmo.asu.edu/

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

New references for high temperature measurements

Summary of work reported for high temperature measurements from NPL

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 outlines such temperatures.

Recorded: 16 June 2015

Speaker: Emma Woolliams

Last Updated: 10 Sep 2015

Source: http://www.npl.co.uk/science-lectures/new-references-for-high-temperature-measurements

YouTube Video: https://www.youtube.com/watch?v=l4Ws6PiqQ9cs.YouTube video:

Further information

Related areas

The Significance of Thermowells

Consider relevant factors and standards

Thermowell Drawing
Thermowell Drawing
Courtesy ISA InTech

Online — In a May/June 2013 article in InTech Magazine Basics of thermowell design and selection”, author Ehren Kiker describes why thermowells are important and how their key parameters can be determined for a particular use situation.

The article begins:

“When planning for a temperature measurement application, a fair amount of consideration is typically given to sensor selection (e.g., thermocouple vs. RTD) and wiring of the output (e.g., transmitter vs. direct wiring), and how these factors will affect the measurement. Often, by comparison, relatively little consideration is given to the mechanical components of the sensor assembly, particularly the thermowell.

“Of all the components in a typical temperature assembly, a thermowell would seem to be the simplest and least critical. In reality, the thermowell is fundamentally important because it directly and significantly affects the life span of the sensor and accuracy of the measurement. It also protects the closed process, providing plant and personnel safety.”

Click here to read the full article now.

ABOUT THE AUTHOR

Ehren Kiker (ehren.kiker@us.endress.com) is a product manager with Endress+Hauser with more than 15 years of experience in process control instrumentation.

Intech MagazineInTech Magazine provides the most thought-provoking and authoritative coverage of automation technologies, applications, and strategies to enhance automation professionals’ on-the-job success.

There is much more online at: https://www.isa.org/standards-and-publications/isa-publications/intech-magazine/.

About ISA

The International Society of Automation (www.isa.org) is a nonprofit professional association that sets the standard for those who apply engineering and technology to improve the management, safety, and cybersecurity of modern automation and control systems used across industry and critical infrastructure.\

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.

Visit: http://www.tempsens.com/softwares.html

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.

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!/

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

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 OpenClipArt.org

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 www.astm.org and search by the standard designation, or contact ASTM Customer Relations (phone: 877-909-ASTM; sales@astm.org). ASTM International welcomes participation in the development of its standards. For more information on becoming an ASTM member, visit www.astm.org/JOIN.

For more news in this sector, visit www.astm.org/sn-consumer 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; cmeyer@nist.gov

ASTM Staff Contact: Christine DeJong, Phone: 610-832-9736; cdejong@astm.org

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 www.astm.org/ABOUT/overview.html.

Mercury Thermometers & Alternatives in the USA

Thermometer Image
Thermometer Image: Courtesy FreeDigitalPhotos.net & mistermong

USA — The USA’s National Institute for Standards and Technology (NIST) began an active mercury-reduction campaign in 2007, and stopped calibrating Mercury (Chemical symbol: Hg) thermometers entirely on March 1, 2011.

A full range of thermometric calibration services continues for non-mercury devices according to the special NIST webpage at: www.nist.gov/pml/mercury.cfm

Mercury is a potent neurotoxin, and every thermometer that contains it is a potential environmental threat. In the 21st century, however, that is a risk that no one needs to take, and a worldwide effort is underway to deploy substitute devices (alternatives) in consumer, professional, and industrial applications.

New analog thermometers with safe filling materials are in production at several companies and recent ASTM standards have been developed to cover them. See ASTM Standards E1 (www.astm.org/Standards/E1.htm) and E2251 (www.astm.org/Standards/E2251.htm).

For more information on each, click each standard’s title (above).

Digital thermometry technologies are plentiful, trials versatile, and generally superior to modern variations on the mercury-in-glass design. Many of these digital devices have wider effective temperature ranges, and nearly all of them equilibrate about 10 times faster than Mercury-filled devices.

There are three classes of sensors that produce signals which can be converted into a digital temperature read-out: thermistorsplatinum resistance thermometers and thermocouples. For more information on each, click on the name on on their name.

Each sensor type used is digital thermometers uses a slightly different aspect of a well-characterized relationship between temperature and electrical resistance or induced voltage in certain materials.

The term “thermometer,” when used in the context of digital equipment, refers to electronic systems that capture signals from the sensors, convert them into temperatures using conversion methods compatible with ASTM and/or ITS-90 standards, and then display the result in some format.

The accuracy of digital thermometers thus depends on the sensor type used, the sensor’s quality, its calibration, and conformance to specified standards. Plus,  the conversion system’s electronics, it’s calibration and conversion technique used and the unit’s sensitivity to ambient temperature and other conditions result additional sources needing traceable calibration.

In many modern devices, these details can be transparent to the user and summary details are described in the unit’s ‘System” calibration certification.

If not, then it is the responsibility of the user to assure that all major components of the measuring system have certified, traceable calibration and then perform the required calculations to determine the system’s measurement capability and combined measurement uncertainty.

This is not always an easy task, but is quite straightforward, as described in the NIST Publication: NIST/SEMATECH Engineering Statistics Handbook (http://www.nist.gov/itl/sed/gsg/handbook_project.cfm)

Reference webpage: Selection of Alternatives to Liquid-in-Glass Thermometers

Promoting alternatives to mercury thermometers

Thermistors

Thermocouple

Ref: ASTM E230 / E230M – Standard Specification and Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples

Platinum Resistance Thermometers (PRTs)

Standard Specification for Industrial Platinum Resistance Thermometers:
ASTM E1137 / E1137M – 08

Verification Methods for Alternative Thermometers

Background References & Links
(Laws and Regulations),

EPA’s Mercury home page — (www.epa.gov/hg/index.html)

State Regs: 2005 Mercury Compendium www.ecos.org/section/committees/cross_media/quick_silver/2005_mercury_compendium1/

The Environmental Council of the States
50 F Street NW Suite 350,
Washington, DC 20001

Tel: +1  202-266-4920
Fax: +1 202-266-4937
Email: ecos (at) ecos (dot) org
Website: www.ecos.org