The Use of Johnson’s Criteria for Thermal Infrared Camera & Systems Performance

Written by: Opgal staff writers  (August 03, 2017)

OPGAL Blog LinkOnline —  When customers are considering which thermal security camera or system to buy, one of the first questions asked of thermal imager manufacturers is usually: “At what distance can the IR camera detect a target?.

In other words, what is the camera’s ability to capture very small details at great distances?

When thinking about effective surveillance, it is indeed a good criterion to differentiate one sensor from another.

No matter which manufacturer you are buying from, the answer given to this question will almost always include the DRI ranges expression.

DRI refers to the distance at which a target can be Detected, Recognized, or Identified, based on certain universally accepted parameters.

In order to select the right sensor for your defense, security, or surveillance needs, these DRI ranges have to be, first, perfectly defined, but also assessed with regards to globally adopted industrial standards.

Enter: The Origin of Johnson’s Criteria

In 1958, at the first ever “Night Vision Image Intensifier Symposium”, John Johnson, a night vision scientist at the U.S. Army’s “Night Vision and Electronic Sensors Directorate” (NVESD), presented a paper named the Analysis of Image Forming Systems”.

Johnson’s paper defined a clear system with criteria and methodology for predicting an observer’s ability to find and assess targets using image intensifying equipment (such as thermal cameras), under various conditions. It worked well, and it was the first of its kind.

Johnson’s Criteria Definitions

Johnson’s model provided definitive criteria for calculating the maximum range at which “Detection, Recognition, and Identification (D, R, I)” could take place, with a 50% probability of success. (Orientation was also discussed, but this parameter is not used or recognized today).

Although newer methodologies for D,R,I exist today, such as NVESD’s “Night Vision Image Performance Model” (NV-IPM), the “Johnson’s Criteria” system was groundbreaking for its time, was the accepted standard in the defense industry for many years, and is still widely used in the security industry today.

Detection

Johnson defined “Detection” as the ability to subtend 1 TV line pair (+/- 0.25 line pairs) across the critical dimension of the subject (this translates to 2 pixels when using an LCD monitor). At the range that this occurs, regardless of target type, the observer could detect that a subject was in the field of view, 50% of the time. Today, many security camera companies loosely follow Johnson’s Criteria and define their camera’s “Detection” performance range as the ability to subtend either 1.5 or 2 pixels on the target, using various target sizes.

Recognition

Johnson defined “Recognition” as the ability to subtend 4 TV line pairs (+/- 0.8 line pairs) across the critical dimension of the subject (this translates to 8 +/- 1 pixels when using an LCD monitor). At the range that this occurs, regardless of target type, the observer determines the type of subject, a human or a car for example, 50% of the time. Today many security camera companies typically define their cameras “Recognition” performance range as the ability to subtend 6 pixels on the target, using various target sizes.

Identification

Johnson defined “Identification” as the ability to subtend 6.4 TV line pairs (+/- 1.5 line pairs) across the critical dimension of the subject (this translates to 12 +/- 3 pixels when using an LCD monitor). At the range that this occurs, regardless of target type, the observer could detect the subject.

Today many security camera companies loosely follow Johnson’s Criteria and define their cameras “Identification” performance range as the ability to subtend 12 pixels on the target, using various target sizes.

Long range performance

Johnson’s Criteria in the Security Industry

DRI ranges, expressed in kilometers (or miles), can usually be found in the specification table of infrared camera brochures, or in a description of the cameras features. While a very helpful jumping off point for narrowing down the options and homing in on the best systems, customers would be doing themselves a disservice to only look at DRI.

This is because today the application of Johnson’s criteria varies somewhat across the security industry. In most instances, documentation uses simplified or modified versions of the criteria, but they do all generally follow similar rules.

Typically, most companies use twelve pixels on the target for identification, six for recognition, and two for detection (sometimes 1.5). However, the target size can vary greatly. Normally the defense industry “NATO” target size (2.3×2.3 meters) is used for calculating the performance range for detecting vehicles, but for a human target, various target sizes can be found.

It is important when selecting your thermal infrared camera to keep in mind that in any given document, the target size for a human can range from 1.7-1.83 meters tall and from 0.3- 0.75 meters wide, and factor this into your decision-making process.

The Need to look at the Bigger Picture

Because end-users often place a high value on the written specifications of the camera, marketing departments are under pressure to use performance calculations that make their cameras look better than the competitors. However, since these calculations typically do not take environmental factors into account, customers should ask their thermal camera providers to explain the other elements and benefits of each camera they are offering, and how they will perform in a variety of conditions.

A modified approach that considers parameters such as these can better help in choosing the right or system for your needs.

The post appeared first on OPGAL.com.

Using Thermal Infrared in “Furnace and Heater Tube Inspections”

by Ron Lucier, ASNT NDT Level III

(From the IRInformIR.blogspot.com, September 27, 2017 with format altered for easier reading online – all text and images from IRInformIR)

ITC logo registered“One of the more challenging applications of infrared thermography is in the measurement of process heater and furnace tubes. In fact we get dozens of inquiries each year from our clients on this very subject.

“Since this is a very complex subject it is probably appropriate to start from the beginning.”

“Process Heaters”
There are as many uses for process heaters as there are designs. The basic configuration consists of a shell (outer casing), tubes (where the process fluid flows) and a heat source.

“These units are both thermodynamically and hydraulically complex.”

Process heater or furnace diagram

“In the simple drawing above we illustrate convective gas flow, which is turbulent, and radiant heat from the flame, refractory and other tubes – all non-uniform and time varying. When you view tube from an access port typically you can only see a portion of the tube or the tube at an oblique angle.

“Therefore, the odds are stacked against you from the start!”

“Why are heater tubes of interest anyway?”
Heater tubes 1“There are several reasons for inspecting tubes. Qualitatively slag (scale) buildup on the outside of the tube can be readily identified.

“Buildup on the inside of the tube (coking) is a bit more difficult but commonly performed.

“In both cases the slag or coke prevents the transfer of heat into the process fluid. In the case of slag buildup, the process fluid may not be sufficiently heated, affecting downstream processing.

“The case of coking on the inside of the tube is more serious. Since the coke has an increased resistance to heat transfer, the tube surface temperature increases.

“After all it is the flow of the process fluid that is keeping the tube “cool” in the first place.

“In fossil boilers this is called “DNB” – Departure from Nucleate Boiling and is usually caused by flame impingement, which initiates a layer of steam on the inside of the tube. The external tube surface, unable to conduct its heat to the water, increases dramatically, causing a failure (opening) in the tube.”

Read more »

ED NOTE: The SPIE has published a very useful and detailed book in its Tutorial Text Series entitled
Radiation Thermometry: Fundamentals and Applications in the Petrochemical Industry
Author(s): Peter Saunders (August 2007) that deals with this topic in depth from the point of view of non-contact temperature measurement (radiation thermometry). It contains a wealth of detail about the issues of slag and reflected thermal radiation as well as a useful tutorial on infrared temperature measurement.

It is available online at the SPIE bookstore at a modest price as both a softcover book and a pdf download.

The link is: https://spie.org/Publications/Book/741687.

Here’s some details from the (above) linked SPIE web page:

Book Description

This tutorial text provides an introduction to the subject of radiation thermometry, focusing on sources of measurement error and giving advice on methods for minimizing or eliminating these errors. Topics covered include: blackbody radiation, emissivity, reflection errors, and atmospheric absorption and emission; commonly used radiation thermometer types; uncertainty calculation; and procedures for in-house calibration of radiation thermometers. Included is a chapter containing detailed measurement examples for a variety of furnace types and operating conditions found in the methanol, ammonia, and refining industries.

Book Details
Date Published: 3 August 2007
Pages: 176
ISBN: 9780819467836
Volume: TT78

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)

Thermocouple App Notes Series, 1 of 4 – Thermocouple Fundamentals

App notes on how TCs work & their calibration

Thermocouple App notesOnline — Thermocouples are broadly used in many industrial and scientific applications. But it can be a bit tricky to understand how they work and how to calibrate them.

Fluke Calibration has developed a thermocouple application note series created by temperature calibration experts to help you learn what you need to know.

The series covers how thermocouples work, choosing calibration equipment, calculating uncertainties, and how to calibrate thermocouples.

There are four application notes in the series:

Visit the webpage at Fluke calibration where you may download the app notes directly: http://us.flukecal.com/blog/thermocouple-calibration-what-you-need-know

Calibration and Metrology training Webinars

Calibration and Metrology training Webinars by Fluke CalibrationCalibration and metrology training webinars are free and offer real-world expertise and practical tips about electrical, flow, pressure, RF and temperature calibration and metrology.

New webinars are added monthly.

If you would like to be the first to know about new seminars, sign up for Fluke Calibration’s metrology and calibration training webinar alerts.

If you can’t find the topic you seek, they may have already covered it.

View their list of 90+ on-demand calibration and metrology training webinars to find out.

A calibration bath primer

Courtesy of FLUKE Corporation

FLUKE Calibration Bath

I’m a big fan of calibration baths.

When I managed our temperature calibration laboratory, I relied on them.

With a series of baths and a liquid nitrogen comparator, we were able to perform a large volume of accredited temperature calibrations with lower uncertainties from -197 °C to 500 °C than would have been possible in any other way.

By Ron Ainsworth from FLUKE Calibration.

Read the Fluke Calibraion Bath Primer online

Ron Ainsworth is the Business Manager for Process Calibration Tools at Fluke Calibration. After graduating with a degree in physics in 1998, he started in the primary temperature calibration laboratory in American Fork Utah.

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/

Thermography Training

Training Program Providers For (IR) Thermographers

Infraspection' Institute's Distance Learning Program for Thermographers

The practice of Infrared Thermography has been recognized by The American Society for Non-destructive Testing, ASNT. They have defined skill levels, written a Handbook, administer skills testing and certify several skill levels of practitioners.

The actual training and refresher skills programs are provided by private training organizations. Some offer their own certifications, but the ones that appear to count to the companies that most utilize them are the ones that prepare individuals for the ASNT exams in the USA.

Listed below are most, if not all, of the companies that offer training programs in North America. If your organization belongs here, let us know to help us get you listed.

We especially seek training listing for countries outside North America since this web site has a wide international distribution. Our visitors come from more than 100 different countries.

  • The Academy of Infrared Training
    A global, independent educational institution devoted to Infrared Thermography training for more than 25 years. (See 2003 schedule below)
  • The Infrared Training Center
    (A part of FLIR with an principle mission of providing Infrared Training in the USA)

    Makes Area thermometers and thermal Imagers and trains users. Sign up for their email newsletter!
  • The Infraspection Institute
    The early pioneers in infrared thermography training. Headquartered in Burlington, NJ (near Philadelphia, PA).
  • The Institute of Infrared Thermography
    Infrared Training Ltd have delivered Infrared Thermography training courses in many locations across the UK, Europe, Middle East and Africa. They are not affiliated with any camera manufacturer, yet offer quality training on all makes and models of infrared equipment. Our company focus is to continue to raise the standards within the field of Thermography by delivering high quality training based on ISO 18436 and ASNT SNT TC 1A standards.
  • JCDPublishing.
    A publisher of specialty books and training materials on Infrared cameras, computer software and thermal imaging applications headed by Gerry Holst, a well-known expert on thermal imaging technology in the IR community.
  • LETA-The Law Enforcement Thermographers Association
    A specialty organization for Law Enforcement Training in the proven uses of Thermal Imaging for Law Enforcement organizations throughout North America.
  • Monroe Infrared Technology
    Infrared Process Cameras, Security Systems, Software and Training Programs.
  • Safe-IR
    A specialty organization for Fire Department Personnel Training in the safe and beneficial uses of Thermal Imaging in firefighting.
  • The Snell Group
    A widely known Infrared Thermography training organization that also provides training for Electrical Motor Inspectors..

Thermography Resources:

Organizations & Meetings

Some of the organizations and meetings shown below are run by training companies and one, the Annual Thermosense Conference, is a technical conferences for thermographers and others involved in R&D, Equipment Development, Process applications and other uses in both Imaging and Sensing via infrared means.

This latter meeting usually runs for 3 1/2 days in the Spring, rotating between Orlando Florida, Baltimore, Maryland and Anaheim, California. It is held in conjunction with a large equipment exhibition and several high tech conferences, all under the banner of a SPIE (The International Society for Optical Engineering) meeting.

  • African Thermograpy User Group
    An Association of Thermography organizations in Southern Africa with about 12 members. Web site has references to training programs run by nearby office of Asea Brown Boveri(ABB).
  • ASNT
    The Association for Non Destructive Testing
    in Columbus Ohio, USA. There are other national organizations around the world affiliated with ASNT and links to them are on this web site.
  • ASTM International
    The American Society for Testing and Materials is one of the largest developers of voluntary consensus standards in the world. There are several committees within ASTM that are active in developing and maintaining standards related to Non-contact temperature measurement and thermal imaging in NDT/NDE.
  • IR/Info
    A Web site and Annual Training Conference with lots of information, Also a connections to an Internet discussion forum, sponsored by The Infraspection Institute.
  • InfraMation
    An e-Newsletter and a topical meeting sponsored by The Infrared Training Center, division of FLIR-InfraMation 2003 is already in the works, and is planned to be held in Orlando, Florida. Contact abstracts@inframation.org.
  • JCDPublishing
    Winter Park, Florida (USA) A publisher of specialty books related to IR and thermal imaging, Also runs training courses for organizations including SPIE. Run by a well-known specialist in IR imaging technology, Gerry Holst.
  • Professional Thermographers Association
    Provides a Directory of Infrared Consulting Companies, Key Points to Choosing an Infrared Consulting Company , Specifications to consider when contracting an Infrared Consulting Company and Generic Specifications for the contracting of an Infrared Electrical / Mechanical PdM inspection to insure that you get a quality job.
  • The Quantitative InfraRed Thermography Conference
    An international conference. Up to now, there has been twelve QIRT conferences (see Archive Section for the complete list).
  • The Snell Group
    An organization that provides many training courses for both Infrared Thermographers and also Motor Inspectors,
  • SPIE Thermosense
    A broad, topical meeting for the international IR Thermal Imaging and sensing technology community. Program on the Thermosense Web site. View the SPIE website for registration and arrangements information.
  • UK Thermographers Association
    UKTA-A national organization based in Bracknell, England with many many links to the USA and other parts of the world.