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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.
4.10
Field
Calibrators Make Everything Better - Users Are
Opening Their Eyes to How Much Clearer Their Data Is - and How Much Better Their
Processes Can Run - with Field Calibrators - From www.controlglobal.com
4.10
Martel
Process Calibrators Blog -
Lots of Interesting Calibration Related posts.
4.10
Who
Do You Trust? - Can you Trust your Vendor’s Calibration
Certificate?
4.10
Martel
Calibrator Newsletter - Martel
Matters is an e-newsletter from Martel Calibrators. It provides
information on new and existing products and calibration "tips".
Highlights from the Latest Newsletter include;
- Tips on performing Low Pressure Calibration
- Getting Rid Of Leaks
- Adding Volume To Your System
- Watching Out For Temperature Effects
- Considering Head Pressure Errors
Other General 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.
Instrument
Calibration- Glenn Carlson,
Technical Support, - 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 -thanks to In-Situ Inc
.
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
4.10
Calibration
- Calibration is the validation
of specific measurement
techniques and equipment. At the simplest level, calibration is a comparison
between measurements-one of known magnitude or correctness made or set with one
device and another measurement made in as similar a way as possible with a
second device. This article from Wikipedia covers all the basics pretty well.
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.
4.10 The
Expression of Uncertainty and Confidence in Measurement - M3003 - The
general requirements that testing and calibration laboratories have to meet if
they wish todemonstrate that they operate to a quality system, are technically
competent and are able to generate technically valid results are contained
within ISO/IEC 17025:2005. This international standard forms the basis for
international laboratory accreditation and in cases of differences in
interpretation remains the authoritative document at all times. M3003 is not
intended as a prescriptive document, and does not set out to introduce
additional requirements to those in ISO/IEC 17025:2005 but to provide
amplification and guidance on the current requirements within the international
standard. This 82 page document is certainly comprehensive - from www.ukas.com
4.10
The
Internet resource for the International Temperature Scale of 1990
- Temperature Scale and General Temperature information for metrologists,
scientists, calibration engineers and those with an interest in the temperature
scale and its realisation.
4.10
Standards
Related to Temperature and Calibration - A list of ASTM standards
4.10
Why
Calibrate Test Equipment? - You’re serious about your electrical test
instruments. You buy top brands, and you expect them to be accurate. You know
some people send their digital instruments to a metrology lab for calibration,
and you wonder why. After all, these are all electronic — there’s no meter
movement to go out of balance. What do those calibration folks do, anyhow —
just change the battery? These are valid concerns, especially since you can’t
use your instrument while it’s out for calibration. But, let’s consider some
other valid concerns. For example, what if an event rendered your instrument
less accurate, or maybe even unsafe? What if you are working with tight
tolerances and accurate measurement is key to proper operation of expensive
processes or safety systems? What if you are trending data for maintenance
purposes, and two meters used for the same measurement significantly disagree?
Thanks to the Cole-Parmer
Technical Library.
4.10
The Following Technical Tips are from Advanced
Instruments Inc
What
Is Instrument Calibration and What Does It Do? - Instrument calibration
is one of the primary processes used to maintain instrument accuracy.
Calibration is the process of configuring an instrument to provide a result for
a sample within an acceptable range. Eliminating or minimizing factors
that cause inaccurate measurements is a fundamental aspect of instrumentation
design.
Why
is Calibration Important? - How a properly performed calibration can
improve product performance.
What
Factors affect Calibration? - Once the benefits of a properly performed
calibration are understood, it becomes evident that care must be taken during
the process to prevent potential error sources from degrading the results.
Several factors can occur during and after a calibration that can affect its
result.
|How
Frequently should a Product be Calibrated? - The simple answer to this
question, although not a very helpful one, is “when it needs it.” From
a more practical standpoint, daily or periodically testing the control solutions
of known values can provide a quantitative indication of instrument performance,
which can be used to establish a history.
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.
The Following Papers are from Fluke
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
4.10
Glossary
of Loop Calibration Terms
4.10
Glossary
of Pressure Calibration Terms
4.10
Glossary
of Temperature Calibration Terms
4.10
Measurement
Uncertainty - How does DMM Accuracy affect your next Measurement? -
Measurement uncertainty is an estimate of the possible error in a measurement.
It's also an estimate of the range of values which contain the true value of the
measured quantity. It's also the probability that the true value lies within a
stated range of values.
11.09
The following Calibration Links are from Dickson
Are
All Metrology Labs Alike? - Short answer – NO!!! In fact, to those of
us in the industry who truly know what it takes to recalibrate instruments to
objectively defined standards, a better question might be— Are you using the
equivalent of a meat thermometer to validate conditions in your processing plant
or laboratories?
“Before”
Calibrations Count More than Many Think - As most know,
temperature and humidity dataloggers and chart recorders need to be recalibrated
periodically to ensure this accuracy, and competent quality managers need to
establish schedules for recalibrations that reflect due diligence to monitor
that temperatures and humidity are kept within acceptable and pre-defined
tolerances. But "recalibration" can mean different things, and what
could be termed "recalibration on the cheap" does NOT demonstrate the
accuracy of your recorded data (instruments).
Monitoring
Revisited - While
most pharmaceutical quality managers realize the importance of temperature and
humidity tracking to guarantee both quality and compliance, the way in which
many go about it is adding hidden costs. Technology for temperature/humidity
tracking continues to evolve, and there are numerous time-saving features in
recent temperature/humidity data loggers that can make a difference. On one
hand, some quality managers are doing too much to track temperature /humidity
data, while on the other hand some are doing too little. For many, it’s timely
to revisit temperature and humidity monitoring. Here are some key points to
consider.
Monitoring
Temperature and Humidity - Monitoring temperature and/or humidity
conditions is an essential ingredient of a wide range of quality assurance
applications. There are many common methodological errors, however, in ways that
this task is approached that either compromise quality standards or add
unnecessary time and expense to the monitoring task. Insufficient calibration of
temperature and humidity monitoring instruments is high on the list of
problematic areas. Mismatching technology to the monitoring task at hand is
another problematic area. This article revisits technology trends in monitoring
instrumentation, provide tips on calibration and discuss common methodological
errors that quality managers should avoid.
Calibrate
- How Often? - This article details the various calibration steps.
Get
Before Data - Before data (a.k.a. "as received data")
documents the accuracy of your data logger or chart recorder before it is
calibrated. When your instrument is re-calibrated it is returned to original
specifications. You cannot retroactively obtain "before" data.
1-Point,
3-Point, or Custom Point? - Choosing between 1-Point, 3-Point and Custom
Point Calibrations is very straightforward when you know how calibration REALLY
works...
Calibration
Glossary - A useful glossary explaining calibration terms.
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