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Test and Calibration Instrumentation
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Low
Pressure Calibrations - When
you're performing a low pressure calibration, there are some things you can do
to make the job easier and better (more accurate) - From
Martel Matters Newsletter.
Temperature
Calibrations (Thermocouple Edition) -There
are a few "gotchas" in temperature calibration when we're talking
about T/Cs and RTDs. Each has its own problems, This article will focus on
calibration of T/C instrumentation -
From
Martel Matters Newsletter.
Other Links
Flow and Level Calibration Notes-Thanks to INX Inc - These notes whilst being a little dated are still very useful.
Pressure & temperature calibration notes- Thanks to INX Inc- These notes whilst being a little dated are still very useful.
Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results- Barry N. Taylor and Chris E. Kuyatt - This is NIST Technical Note 1297 as it was published.
U. S. Army Corps of Engineers Process Instrument And Control Checklist - This is a very useful checklist which is designed to facilitate the performance evaluation of process instrumentation and control systems used to operate and monitor treatment processes and equipment.
To calibrate or not to calibrate? - From the UK's National Measurement Laboratory - Covers; What is calibration, How frequently an instrument should be calibrated, Do all measuring instruments need to be calibrated and level of and routes to calibration.
What
is the difference between calibration and adjustment?- From the UK's National
Measurement Laboratory
Instrument Calibration- Glenn Carlson, Technical Support, In-Situ Inc (www.in-situ.com) - Users frequently want to know how often they need to calibrate their In- Situ instrument. The most accurate answer to that question is “it depends”. This article addresses this.
Some Notes on Device Calibration -From the University of Dublin - A comprehensive albeit a bit academic note.
On site flow calibration is painful but necessary- by David W. Spitzer -thanks to ControlGlobal.com .Some new product introductions have raised doubt about what in-situ calibration for flowmeters is, and whether it can be duplicated with simulators and calibrators with expanded diagnostics
Calibration Primer - From Omega.com - The most sophisticated industrial equipment will not be very useful unless it is calibrated. Through calibration, adjustments made to a piece of equipment ensure that it performs as expected—that it can be relied on to deliver predictable, accurate results that meet quality standards. This white paper from Omega Engineering explains what calibration is, why it is important, and how it works. NIST traceability is defined and discussed, and there is a step-by-step description of a basic calibration. This paper also discusses in-house vs. laboratorycalibration, and it describes major types of calibration devices.
Calibrating
and Testing Control Components on your Heat Process - What, When and How Should
I Calibrate? - Arthur Holland, Holland Technical Skills -
an excellent explanation on the basics of calibration
The Following Papers are from BEAMEX
Automated calibration planning lowers costs
- Calibration is an essential element
of any instrumentation
maintenance program. However, sometimes
calibration operations can be long and time-consuming.
By planning the process and adding the right
tools, efficiency can be improved and costs lowered substantially.
Calibrating
Fieldbus Transmitters - Fieldbus is becoming more and
more common in today’s instrumentation. But what is
fieldbus and how does it differ from conventional instrumentation?
Fieldbus transmitters must be calibrated as well, but how
can it be done? Until now, no practical solutions have
existed for calibrating fieldbus transmitters.
How
often should calibrators be calibrated? - This article discusses some of
the things to be considered when specifying the calibration period and provides
some general guidelines. The same guidelines that apply to a calibrator also
apply to other measuring equipment in the traceability chain. These guidelines
can even be used for process instrumentation.
How
often should instruments be
calibrated? - Plants can improve their efficiency and reduce costs by
performing calibration history trend analysis. By doing it, a plant is able to
define which instruments can be calibrated less frequently and which should be
calibrated more frequently. Calibration history trend analysis is only possible
with calibration software that provides this functionality.
Traceable
and efficient calibrations
in the process industry - Today’s modern process plants, production
processes and quality systems, put new and tight requirements on the accuracy of
process instruments and on process control. Quality systems, such as the ISO9000
and ISO14000 series of quality standards, call for systematic and well
documented calibrations, with regard to accuracy, repeatability, uncertainty,
confidence levels etc.
The
Safest Way to Calibrate - An introduction to intrinsically safe calibrators
- There are industrial environments where calibrations should not only be made
accurately and efficiently, but also safely. When safety becomes a top priority
issue in calibration, intrinsically safe calibrators enter into the picture.
Many Technical
calibration papers including the following can be found thanks to Fluke,
you have to register but it is worth it.
A Poor Man's Resistance Bridge
A Preliminary Assessment of the Effectiveness of 5700A Artifact Calibration
A Traceability Technique for Complex Waveform Generators
A Wheatstone Bridge for the Computer Age
An Application of the Guide to Measurement Uncertainty
An Assessment of Artifact Calibration Effectiveness for a Multifunction
Calibrator
Calibration Data Management: Meeting the Reporting Requirements of ISO/IEC FDIS
17025 Future Developments in Oscilloscope Calibration
Maintenance and Calibration of HART Field Instrumentation
Calibrating
Non Destructive Testing Instruments
- NDT Resource Centre- Calibration refers to the act of evaluating and
adjusting the precision and accuracy of measurement equipment. In ultrasonic
testing, several forms of calibration must occur. First, the electronics of the
equipment must be calibrated to ensure that they are performing as designed.
This operation is usually performed by the equipment manufacturer and will not
be discussed further in this material. It is also usually necessary for the
operator to perform a "user calibration" of the equipment. This user
calibration is necessary because most ultrasonic equipment can be reconfigured
for use in a large variety of applications.
A
Guide to Low Resistance Measurement - Note this is
a large 3 MBits download. This handbook gives an overview of low resistance
measurement techniques, explains common causes of errors and how to avoid them.
We have also included useful tables of wire and cable characteristics,
temperature coefficients and various formulas to ensure you make the best
possible choice when selecting your measuring instrument and measurement
technique - from Cropico.
The following temperature calibration links are compliments
of ISOtech
A
review of some of the best articles written about water and its triple
point - Details of articles on this subject.
Calibrating
Thermometers
-Dave Ayres and Anne Blundell - A thermometer without a
traceable calibration route to recognised National Standards is fairly useless.
Yet we all buy mass produced thermometers which are supplied without a
calibration and use them. We all hope that the manufacturer has been
conscientious and has at least carried out calibration checks on batch samples
and has claimed a level of accuracy to the batch. But has the manufacturer used
suitable standards for the calibration?
Calibrating
Thermometers Spanish Language
Improved Sterilizer
Tests - Dave Ayres and Dave Hill - Scottish
Healthcare Supplies Sterilizer Test Group assessed various established methods
of on-site temperature calibration and realised there might be shortcomings in
commercially available "complete" systems. The guidelines require
tests on sterilizer systems to be carried out within a system uncertainty of
±0.5°C but the assessment showed that in many cases "complete"
systems could produce a system uncertainty of ±1.0° or worse. (Temperature
monitoring in sterilizer systems is critical ensuring that microbiological
viability is eliminated from the product).
Industrial
Measurements with very Short Immersion - J. P. Tavener, D.
Southworth, D. Ayres, N. Davies.- One major problem that keeps
recurring is the request to calibrate, or in some other way to evaluate, very
short industrial temperature sensor assemblies. These sensors are so short that
the sensor does not attain the temperature of its surroundings. Two distinct
methods are possible, in method one the assembly is immersed in a comparison
bath sufficiently to eliminate the stem conduction effect, even if this method
creates a different result than achieved in-situ. Method two attempts to
simulate the application in practice and provide a similar stem conduction error
as the assembly sees in practice.
Automating
Temperature Calibration Baths with Simple Low Cost Image Acquisition
- David J. Southworth - A low cost
video camera, “Web Cam” is used in conjunction with a
PC and Temperature Calibration Bath to automatically
calibrate handheld digital thermometers which have no provision to be connected to an external computer.
Automating
Temperature Calibration Baths with Simple Low Cost Image Acquisition
Spanish Language
Stem
Conduction And Light Piping in ITS-90 Fixed Point Cell Assemblies At A
UKAS Laboratory - J. P. Tavener & A. Blundell - Standard Platinum Resistance Thermometers
(SPRTs) with
length-below-handle of only 480mm are regularly submitted for calibration at
ITS-90 fixed points from –200 °C to +660 °C. The length of the thermometer
limits the maximum size of fixed point cell that can be used to calibrate the
thermometers. Stem conduction effects have been measured at zinc and aluminium
temperatures in resealable cells. These have been quantified and eliminated by
adopting a cell design with a very small connection between cell and gas supply.
Slim
Cells An International Comparison - J. Tavener -
This paper presents the results of the original primary laboratory
inter-comparisons and the more recent inter- comparisons
of PTB. The results show that the slim cells and apparatus offer
good agreement with Primary and National Standards.
Temperature
Calibration; Depths of Immersion - John P. Tavener -Of
all the sources of errors and uncertainties in thermal calibration by far
the largest source of error and least understood effect is that of
immersion of unit under test, and the reference standard.
Primary
Laboratory Comparisons
- The most accurate measurements made in a Primary
Temperature Laboratory are during intercomparisons of ITS-90 fixed point cells,
and in particular inter-comparing water triple point cells. To assess the
stability of the water triple point, a laboratory ideally needs to be able to
measure differences of just one or two micro degrees.At the Northern Temperature
Primary Laboratory (NTPL) we found the spread of results too large to give a
satisfactory result. Consulting the literature, and in particular Tischler &
Prado [3] we eventually developed a 3 current technique from which we were able
to calculate the zero current resistance to within 1 or 2 micro degrees. This
paper describes in detail our method.
Recommended Book- Traceable Temperatures - An Introduction to Temperature
Measurement and Calibration - J.V. Nicholas and D.R. White, John Wiley +
Sons, 2nd Edition Download
Chapter One: Measurement and Traceability Purchase
from Amazon.co.uk