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This is an excellent article giving the basics about temperature- Thanks to the University Corporation for Atmospheric Research.
Isotech Journal of Thermometry - This brilliant five part
journal is an excellent collection of technical articles dedicated
specifically to thermometry. It includes articles related to temperature
scales, different methods to realize them and practicle techniques used to
calibrate interpolation devices such as SPRTs, IPRTs, Thermocouples, Thermistors
Welcome to the Isotech Journal Of thermometry - Fundamentals of Thermometry, Part 1: Temperature Scales - Practical Calibration of Thermometers on the ITS-90 - Platinum Resistance Thermometers as Interpolation Standards for the ITS-90
Fundamentals of Thermometry, Part 2: Fixed Points - Standard Platinum Resistance Thermometer calibrations on the ITS-90, How to specify & order - International Equivalence of thermometer calibration, testing & certification - Improvements in Metrological Apparatus - Evaluation of the Gallium melting Point by a two cell comparison - An MS-DOS computer program for the interpolation of ITS-90
Fundamentals of Thermometry, Part 3: Standard Platinum Resistance Thermometers - The Platinum Resistance Thermometers of C.H. Meyers (Historic Reprint) - Coiled Filament Platinum Resistance Thermometers - Open Cell, Sealed Cells, & Slim Cells - The Heat Pipe and its use in Thermometer Calibration - Isothermal Heat Pipes and Press Controlled Furnaces
Fundamentals of Thermometry, Part 4: Standard Thermometers, Bridges & Measurements - Cost of Calibration to ITS-90 at various institutions - Uncertainties in Temperature Measurement - The Gallium Watchdog (in quality assurance of measurement) - New Developments & Discoveries - High Temperature Platinum Resistance Thermometers - Review: About Words - available metrology vocabularies
Fundamentals of Thermometry, Part 5: Industrial Platinum Resistance Thermometers - Common Errors in Industrial Temperature Measurement - I Blame the Mother-in-law (Evolution of a Fluid Bed Calibration Bath) - The Water Triple Point and Gallium Point in Secondary Laboratories in Germany - Comparison Calibration at the Boiling Point of Nitrogen or Argon - A Caution from Phil Metz - News of a new Metrology Society (Slovak Metrological Society) - Melting Point and Triple Point Measurements of Gallium on the IPTS-68 (Historic Reprint)
Measurement and Calibration: what every Instrument Technician should know -
Temperature may be the most commonly measured physical parameter. Yet there have
never been so many ways to measure it as there are today. With so many options
it’s natural to have a few questions. How do I measure temperature? How
accurate is my measurement? What temperature range is required? What type of
device best measures temperature? These are very common questions when
confronted with the need to measure temperature. A variety of measurement
devices may be used for temperature: liquid in glass thermometers (LIG),
thermocouples (TCs), thermistors, resistance temperature detectors (RTDs),
platinum resistance thermometers (PRTs) and standard platinum resistance
thermometers (SPRTs) - Thanks to Fluke and www.processonline.com.au
Challenges of Temperature Sensing - Measuring each of the "big four" process variables has its specific peculiarities, but temperature seems particularly controversial. In fact, this apparently simple task often gets complicated. This tutorial explains why- from Control Engineering Magazine and Moore Industries-Pacific, Inc.
Trends in Process Temperature Measurement -An Evolving Technology Segment Changes Focus to Meet End-User Needs - Mike Cushing - This article also covers the basics about resistance thermometers, thermocouples and the use of temperature transmitters - from www.flowcontrolnetwork.com
NIST Launches New Website to Educate Industry About Alternatives to Mercury Thermometers - As part of a larger effort to reduce the amount of mercury, a potent neurotoxin, in the environment, the National Institute of Standards and Technology (NIST) has launched a new website to help industry scientists and engineers decide the best temperature measurement alternative for their purposes. The website also includes information about myths pertaining to mercury and temperature measurement and how to safely package and recycle mercury-containing products.
Selecting Temperature Measurement and Control Systems - Steve Byrom - How to get accurate data and perform reliable control from systems designed for the rigors of industrial applications - Measuring and controlling temperature is undoubtedly the most common measured parameter because it is critical to so many operations and tasks. Accurate temperature measurement and control is vital to the quality of manufactured goods, such as finished metal components, and to the efficient and safe operation of a process or system. In today’s market, there are myriad devices for monitoring and controlling temperature, ranging from simple temperature controllers to complex distributed control systems. Most temperature measurement and data acquisition products are well-suited for the job for which they are intended, but care must be taken when applying them in harsh industrial environments - from ISA and InTech.
10.13 Industrial Temperature Measurement Engineer's Guide – This 420 page guide from Emerson Process Management is excellent. From the basics to engineering design and white papers it is very comprehensive. You will have to register to get it but it is worth the effort!
Buying a Temperature Controller? - Understand the Specification Before you Order - Arthur Holland - A review some of the features and specifications of the commonly used discrete panel-mounted controllers. A review of all makes and features is impossible here, so to supplement this column, my best advice is, extend your reading to catalogs, operation manuals, FAQs and web sites of the top manufacturers. Technology help lines are so overloaded that they become impenetrable and direct you to existing sources of help. Rightly so - but be prepared to quarry your way through some hard to read material. With product knowledge in your brain and an eye on your process you can make a sound and economical choice of controller.
A useful degree C/F/Kelvin conversion tool - from Raytek
The Majority of the following links are compliments of http://www.temperatures.com , this website is excellent and provides comprehensive technical information on all temperature related instrumentation. ICEweb congratulates temperatures.com on the development of such a great resource.
The principle behind a bimetallic strip thermometer
relies on the fact that different metals expand at different rates as they warm
Bimetallic Thermometers and Thermostats
Emissivity - Emissivity: a mystery to some? But not to all! You can't live with it. You can't live without it - Emissivity is linked to Infrared Radiation Thermometry (or, if you prefer, pyrometry) . It's a mystery to many people, however, even to some who sell non-contact temperature sensors and thermal imagers.mPart of the mystery of emissivity is its spelling, it gets mangled more often than consistant; emmissivity, emistivity, emystery and emisomething are just a few. Seriously, it is the often misunderstood parameter that is always associated with IR temperature measurement and radiation heat transfer ("consistent" is the correct spelling, BTW and emissivity has always had only one 'm'). Heat transfer people have no problems with their emissivities. Are they better educated than some of the users of IR thermometers?
Mercury in Steel Basic principals from the Glossary of Meteorology
Standards for Liquid in Glass Thermometers - Glass thermometers are among the oldest and still the most widely type of thermometer used in laboratory work and in households to determine fever temperature in humans.The first standard issued by ASTM on thermometery was standard E1.
the Right Temperature Sensor - Mick Carolan - Temperature
sensors are an effective way to measure temperature, but which should you use,
and for which application? Thanks to www.pacetoday.com.au
Selecting a Temperature Sensor - Choosing a temperature sensor can often be very straightforward, sometimes tricky, but always worth doing well. That's because these sensors, especially in science and engineering uses, can spell the difference between repeatable results and nonsense numbers. The name of the game in measurement is to measure with an amount of inaccuracy or uncertainty that is acceptable. So, the first thing you need to know is how well you need to know the value of the temperature numbers you expect to get. A simple series of questions, when answered, will usually get you started.
How To Select And Use The Right Temperature Sensor - Ron Desmarais - This paper answers the question "How do I determine which sensor to use in my application?” After a brief review of how RTD’s and thermocouples are constructed and used to measure temperature, it discusses what differentiates these sensors from one another. It covers the topics of temperature range, tolerance, accuracy, interchangeability and relative strengths and weaknesses for each type. After reviewing these topics you will have a better understanding as to when each type of sensor should be used and why. From Pyromation, Inc.
A Comparison of Thermocouple and RTD Temperature Sensors - Many users simply look to fill the basic needs of their application and do not worry much about their choice of temperature sensing technology. That is, they will make a selection based simply on temperature range and their own bias, perhaps based on their familiarity with a particular sensor type. At a minimum, an informed sensor choice should first consider (a) Measurement range, including the range extensions of shutdown, startup, and process upset (b) The response time and (c) The sensor stability, accuracy, and sensitivity in the application environment. The optimum choicebetween thermocouple and RTD can be difficult. There is a lot of overlap between these sensors at the more popular lower end of the operating temperature range. So for sensors that cover the same operating range, and applications where response time is not a driving issue, plus stability, accuracy, and sensitivity are acceptable, it is necessary tocompare characteristics between sensors to find the best fit for a given application - from Acromag.
Choosing a Temperature Transmitter -From Moore Industries International - While there are many practical and economic advantages to using temperature transmitters, the most basic are to ensure measurement integrity and to convert a temperature sensor’s low-level (ohm or millivolt) signal to a standard 4 to 20 mA current signal that can be readily accepted by a monitoring and control system. Advancing technology has made the use of temperature transmitters affordable even in cost-sensitive applications. Here are few things to consider when choosing one. Thanks to Process Heating Magazine
Sensor Types - Big differences exist between different temperature sensor or temperature measurement device types. Using one perspective, they can be simply classified into two groups, contact and non-contact. The two links in this article take you to descriptive pages on each type with a breakdown by more specific, detailed types.
Temperature Sensor Uses, Measurements or Applications - Measurements are where temperature sensors meet the "real world" where results prove that one understands their properties and has selected a sensor well enough to do the job within the desired measurement uncertainty. This link is where the real fun begins for anyone trying to make a serious temperature or dewpoint measurement. It highlights web sources for this information.
Thermometers - What are RTD's? -Resistance
Temperature Detectors or RTDs for short, are wire wound and thin film devices
that measure temperature because of the physical principle of the positive
temperature coefficient of electrical resistance of metals. The hotter they
become, the larger or higher the value of their electrical resistance.
Resistance Tables - Thanks to Emerson Process Management
All you want to know about Resistance Thermometers - A 53 page document from Eurotherm
Standard Platinum Resistance Thermometers - Frequently Asked Questions - From ISOTECH
The Basics of Temperature Measurement Using RTDs - This paper provides information for choosing a Resistance Temperature Detector (RTD) sensor type. After a review of the basic construction of an RTD it looks at an RTDs Temperature Coefficient of Resistance (TCR), its sensitivity, accuracy, interchangeability, repeatability, stability and drift, corrosion and contamination effects, shock and vibration effects, insulation resistance, lead-wire resistance, self-heating effects, meter-loading, packaging and thermalransfer considerations, response time, and thermoelectric effects - from Acromag.
and Answers on Infrared Thermometers - A useful technical
information sheet from our sponsor Zedflo
Infrared Thermometers - from Omega.com
Principles of Non-Contact Temperature Measurement - This manual focuses on the practical operations of non contact temperature measurement devices and IR thermometry, and answers important questions that may arise - from Raytek
Emissivity - This is the measure of an object's ability to emit infrared energy. Emitted energy indicates the temperature of the object. Emissivity can have a value from 0 (shiny mirror) to 1.0 (blackbody), this technical article provides further information on this including emissivity tables for metals and non metals - from Raytek
Millivolt Tables - Thanks to Emerson Process Management
Thermocouple - A good introduction from Wikipedia, the free encyclopedia
All you want to know about Thermocouples - A 53 page document from Eurotherm
Thermocouple Theory and Practice - W. Dhavepatana Co., Ltd, a neat site this one.
Thermocouple Compensating Cables- See Pages 7 to 9 of this comprehensive document from Eurotherm
Thermocouple Extension Cable Tables - Data and colours from Raychem Thermocouple Wire- Some of the questions answered by Omega
Traps and Colour Confusion in Thermocouple Wiring - A useful reference from Arthur Holland and Eurotherm
Thermocouples - Greg Passler answers the following questions: What is a thermocouple and how does it work? Why do we use thermocouples? What is thermocouple extension cable? From Shawflex
Taking Thermocouple Temperature Measurements- From NI Instruments
The Care and Feeding of Thermocouples - Richard D. Smith, P.E - This is a absolutely superb paper.
How to Prevent Temperature Measurement Errors When Installing Thermocouple Sensors and Transmitters - This paper reviews thermocouple behaviour and outlines some of the problems that people encounter when connecting to thermocouples to measure temperature. It contains helpful information for minimizing system error so that you can get the best possible performance from your thermocouple temperature measurement system. It is written primarily for industrial users of thermocouples and thermocouple transmitters, but much of this information can be extended to any thermocouple instrument - from Acromag.
The Basics of Temperature Measurement Using Thermocouples - This paper looks at important characteristics the thermocouple. There are important points about thermocouples that must be understood and this white paper will help you to make an informed selection between sensor types and avoid potential problems in your application - from Acromag.
7.13 Get Rid of Rigid - The WORM Flexible Temperature Sensor - Flexible temperature sensors are the new frontier in accurate temperature measurements and easy maintenance. The WORM’s mission: to fit nearly everywhere, to be quickly cut to the correct length, and to reduce the number of spare parts a plant has to keep on hand. The WORM is a flexible sensor for thermowell temperature assemblies. It was designed to replace restrictive, rigid, straight sensor probes with a universal strategy that saves time and money. When it comes to flexible and rigid temperature sensors, both can be inserted into thermowells or protection tubes, welded into place on boiler tubes or other objects, or clamped down for surface measurements. Both types of sensors are rugged, durable, and can measure a wide range of temperatures in industrial applications. So, why replace rigid, straight sensors? From Moore Industries. Additionally see a Video outlining the features here.
Thermistor Resistance Table - from Minco
6.13 Thermistors As Accurate Temperature Sensors - Introduction and Methods - Darren O'Connor, and Kasandra O'Malia - This two-part article describes how to use a simple voltage divider circuit with a thermistor to achieve high-accuracy temperature readings over broad measurement ranges. Part 1 discusses the circuit and various temperature estimation methods. Part 2 of this two-part article shows a method to a real-world application and how, by combining estimation methods with thermistor characterization data, high accuracy measurements can be achieved over a wide temperature range using the simple voltage divider circuit - from Sensors Magazine.
Liquid in Glass Thermometers
Following are a number of technical articles on the new Thermowell Design
Standard ASME PTC 19.3 TW-2010, the correct design of thermowells is very
important especially in respect of stress failures - this standard addresses
New Standard for Thermowell Design - ASME PTC 19.3 TW - 2010 - The long awaited PTC 19.3 TW-2010 is a completely new standard that establishes the practical design considerations for thermowell installations in power and process piping. This code is an expanded version of the thermowell section contained in the PTC 19.3-1974, and incorporates the latest theory in the areas of natural frequency, Strouhal frequency, in-line resonance and stress evaluation. ASME responded to changing industry demands for a more comprehensive set of thermowell evaluations. Key enhancements over the 1974 edition include:
Expanded coverage for thermowell geometry;
Natural frequency correction factors for mounting compliance, added fluid mass, and sensor mass;
Consideration for partial shielding from flow;
Intrinsic thermowell damping;
Steady state and dynamic stress evaluations;
Improved allowable fatigue limit definition
PTC 19.3 has been the standard used by piping designers since
it’s release and has been highly successful in the industry. The new,
expanded PTC 19.3 TW edition—developed by end users and
manufacturers—builds on decades of industry and research data to make
it the new worldwide authority for thermowell design safety. Intended
for piping designers, instrument engineers, instrument designers and plant
I/C engineers/designers, plant engineers, plant safety engineers, process
engineers, thermowell manufacturers, instrument manufacturers, anyone who
assembles thermowell bids or design specifications, and regulatory agencies.
Thermowell Calculations - A white paper from Emerson Process Management - Dirk Bauschke, David Wiklund. Andrew Dierker and Alex Cecchini - Thermowells are essentially a circular cylinder installed like a cantilever into the process piping. They allow a temperature sensor to be located within a process flow while providing a process seal and protecting the sensor from the process fluid. As a process fluid passes around the thermowell, low pressure vortices are created on the downstream side in both laminar and turbulent flow. The combination of stresses, generated by the static in-line drag forces from fluid flow and the dynamic transverse lift forces caused by the alternating vortex shedding, create the potential for fatigue-induced mechanical failures of the thermowell. Until recently ASME PTC 19.3-1974 has been the standard by which most thermowells are designed. For the most part, though, ASME PTC 19.3-1974 was used successfully in both steam and non-steam applications. Several key factors caused ASME to re-form the committee in 1999 to completely rewrite the standard; advances in the knowledge of thermowell behavior, a number of catastrophic failures (Monju among them) and the increased use of Finite Element Analysis for stress modeling. When combined, these factors caused many in the industry to move away from the rudimentary methods and simplified tables laid out in ASME PTC 19.3-1974 in favor of more advanced methods for predicting the thermowell natural frequency and calculating the forced frequency. Rather than simply update the existing version of ASME PTC 19.3-1974, the committee decided to release a new standard due to the significant changes associated with the effort. The thermowell calculation portion of ASME PTC 19.3-1974 was 4 pages. By comparison, the new standard, known as ASME PTC 19.3TW-2010 (“TW” for thermowell), is over 40 pages due to the explanations of theory and the sheer complexity of the process. By February 2010, ASME PTC 19.3TW-2010 was approved through all applicable committees and it was finally released in July 2010.
Thermowell Design Standard ASME PTC 19.3 TW-2010 - An explanatory video - from Emerson Process Management
Typical Thermowell Calculations Report per ASME PTC 19.3TW-2010 - From Emerson Process Management
Velocity Collars: No Longer Best Engineering Practice - A velocity collar is a metal ring machined into the shank of a thermowell and installed tightly in to the standoff of a pipe. Due to the nature of thermowell vibration behavior, installation practices, and ASME’s position, Emerson does not recommend velocity collars as a best practice for means of reducing vibration-related failure. Emerson also feels that other installation methods that attempt to reduce unsupported length in a similar fashion to velocity collars, such as DIN Weld-in style thermowells, are not a best practice.
Do Your Thermowells Meet the ASME Standard? - Thermowell design has become more conservative in the age of ASME/ANSI 19.3TW-2010 - Mitchell P. Johnson, J.D. and Allan G. Gilson, P.E. - Depending on process conditions there are a number of other factors that can cause a thermowell to suffer mechanical failure at insertion lengths less than one-third of the pipe. These include flow-induced vibration (wake frequency failure), dynamic (oscillating) and steady state stress, pressure, corrosion, erosion, material selection, and improper installation technique. All of these must be considered in properly designing a thermowell for a given installation. So who is responsible for making the judgment call here? The 19.3TW standard makes plain that ultimate design responsibility for a thermowell well rests with the engineer designing the system into which the well is being installed: Specification of a thermowell, including details of its intended installation and all intended operating conditions, is the responsibility of the designer of the system that incorporates the thermowell. The designer of that system is also responsible for ensuring the thermowell is compatible with the process fluid and with the design of the thermowell installation in the system - from Flow Control.
7.13 Basics of Thermowell Design and Selection - Do not underestimate the importance of thermowells in temperature measurements - 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 - from ISA and InTech.
10.13 Chloride Induced Stress Corrosion Cracking of Stainless Steel Thermowells: Potential for Ingress Of Atmospheric Moisture - This safety notice from the HSE describes a specific degradation mechanism found inside stainless steel thermowells operating where the external atmosphere contains halides, as is typical in coastal locations or near to cooling towers. Thermowells can ‘breathe’ during normal operation as vessels heat up and cool down, drawing in the external atmosphere through non gas tight fittings. If the atmosphere contains halides this can leave any stainless steel susceptible to Chloride Stress Corrosion Cracking (CISCC).
is a thermowell? From-Trerice
About Thermowells -A super page from Temperatures.com covering most aspects including the one most forgotten related to velocity constraints.
Thermowell Wakes, Vortices, Vibrations & More- Another top rate page from Temperatures.com covering most aspects
Introduction to Thermowells - From Newport
Thermowell Materials Selection Guide - From Azom.com
Scales and Conversions
Calculate temperature and millivolt tables for Thermocouples based on NIST Monograph 175 - From MINCO
Calculate temperature and resistance tables for Minco's RTD Elements - From MINCO
Temperature Regulators - The characteristic feature of self-operated temperature regulators is their compact design, including a sensor, a valve and a capillary tube. Their simple operating principle is based on fundamental mechanical, physical and thermodynamic laws. Thanks to our valued sponsor Samson Controls.
Temperature Sensor Calibration Resources