Resources

Calibration of Stopwatches

Technical Guide 8

How to obtain a traceable calibration of a stopwatch using the MSL talking clock. Includes details on the use of the clock and the uncertainty to be expected.

Uncertainty Calculations for Remote Clocks

Technical Guide 9

This guide describes the uncertainty calibrations made for the measurements reported in the MSL time and frequency bulletins and recommends a method for users of the bulletins to calculate the uncertainty in the frequency of their remote oscillator.

Impedance (RLC) Standards

Technical Guide 27

The ac measurement of resistors, inductors and capacitors (R, L and C) requires a clear understanding of exactly what is being measured. This guide aims to help owners of impedance standards make the best use of their equipment. Part I explains the information provided in a typical calibration certificate for an impedance standard and Part II gives general advice on using the impedance standards.

Phase and Sign Conventions for Energy Meters

Technical Guide 28

The relationship between voltage and current in a system being metered can be expressed in several ways, e.g., by a power factor, a phase angle, or by describing the load as inductive or capacitive. This is straightforward when the system being metered is a net consumer of power and the phase angle is between +90° and −90°. It is less clear when the system is generating power and the phase angle exceeds 90°.

Electricity Metering: Advice for Class B Approved Test Houses

Technical Guide 33

The Electricity Authority has specified the requirements for electricity metering in Part 10 of the Electricity Industry Participation Code. Class B Approved Test Houses have many responsibilities placed on them by the code to assure the trustworthiness of the metering that they install and maintain. This guide offers practical advice on how to manage measurement uncertainty from design to installation without needing to carry out specialist in-depth uncertainty calculations.

Spectral Mismatch of Illuminance Meters

Technical Guide 34

Illuminance meters are commonly used in industry to ensure lighting is at an appropriate level to demonstrate compliance for purposes such as health and safety and inspection. They can be purchased relatively cheaply but how good an instrument are they? This technical guide explains one of the most critical components of illuminance meter characteristics, the spectral mismatch, and the likely magnitude of error this effect can lead to in common commercial light meters.

Reference Materials for the Calibration of UV/visible Light Spectrophotometers

Technical Guide 38

This guide provides information about reference materials that can be used when calibrating or checking the performance of a UV/visible light spectrophotometer. The known absorbance of reference materials at particular wavelengths can be used to validate the scale of absorbance (photometric accuracy), the wavelength accuracy of a spectrometer and identify stray light problems.

Magnetic Effects in Weighing

Technical Guide 6

An introduction to magnetic effects in weighing and how to avoid them. Includes a description of MSL’s facility for measuring the magnetic properties of weights. Suitable for anyone using or calibrating balances, or calibrating weights.

Assuring the Quality of Weighing Results

Technical Guide 12

This technical guide covers quality assurance aspects of the use of electronic balances and other weighing devices, including calibration, in-service checks and acceptance criteria, control charts, and check weights.

Pressure Gauge Calibration

Technical Guide 13

This technical guide outlines a method to calibrate a pressure gauge and calculate the uncertainty of the gauge corrections. The method is suitable for gauge calibration laboratories accredited to ISO 17205 and can be applied to any pressure gauge or transducer calibration.

Care and Use of a Deadweight Tester

Technical Guide 16

Deadweight testers, also known as pressure balances or piston gauges, are stable instruments, with long recalibration intervals, that can reliably generate pressures with a small uncertainty. To assure this stable behaviour between calibrations the deadweight tester has to be operated correctly and looked after well.

Measuring Volume by Weighing Water

Technical Guide 17

This guide describes a method for measuring the volume of a vessel by weighing the water it can contain (or deliver). The method is suitable for vessels such as burettes and pipettes, and can also be applied to the calibration of water flowmeters. The guide covers the necessary calculations, measurement uncertainties with an emphasis on repeatability, and some practical details.

Measuring Atmospheric Pressure with a Barometer

Technical Guide 19

This guide explains how to use a digital barometer to measure atmospheric pressure in a laboratory or industrial setting. It starts with a brief discussion of the atmosphere and then talks about barometers, their stability and calibration requirements, along with how to work out the uncertainty of an air pressure measurement.

Calibrating Balances

Technical Guide 25

A method for calibrating balances is described in this technical guide. It includes pre-calibration steps, the measurements to be recorded and their analysis, the evaluation of measurement uncertainties and the reporting of results. This method, which is taught in the MSL Balances and Weighing workshop, is focused on electronic top-loading balances but applies to most modern weighing devices.

Calibrating Piston Pipettes

Technical Guide 30

This technical guide describes a method for calibrating both fixed volume and variable volume piston pipettes with volumes from below 1 µL to above 10 mL. The guide covers the necessary equipment, the method and how it relates to ISO Standards for piston pipettes, the necessary calculations and the measurement uncertainties. It also addresses the method uncertainty associated with calibrating pipettes to ISO 8655.

Calculating Deadweight Tester Pressures

Technical Guide 36

This technical guide describes how to calculate pressures generated by a deadweight tester, or pressure balance, for use in calibrating pressure-measuring instruments. It is applicable to hydraulic and pneumatic deadweight testers that generate gauge pressure (including negative gauge pressure), where a relative uncertainty in pressure of 0.003 % (30 ppm) or greater is required.

The Ice Point

Technical Guide 1

How to make a simple temperature reference at 0 °C accurate to 0.01 °C. Suitable for anyone using liquid-in-glass thermometers, thermocouples, thermistors or platinum resistance thermometers.

Infrared Thermometry Ice Point

Technical Guide 2

A simple procedure for checking low-temperature radiation thermometers at 0 ºC.

Uncertainties in the Realisation of the SPRT Subranges of ITS-90

Technical Guide 3

The MSL technical guide TG3: "Propagating uncertainties in the SPRT subranges of ITS-90" has been superceded by the more helpful document Uncertainties in the realisation of the SPRT subranges of ITS-90 published by the BIPM's Consultative Committee for Thermometry (BIPM, Interntional Bureau of Weights and Measures, www.bipm.org ). The guide explains all of the sources of uncertainty in the use and calibration of standard platinum resistance thermometers (SPRT), and gives the expressions for total uncertainty for a wide range of measurement senarios.

Icepoint Humidity Generator

Technical Guide 4

How to construct a simple single point humidity generator using MSL Technical Guide 1 (The Ice Point) as the saturator temperature controller. Useful for routine spot checks of dew point meters and relative humidity hygrometers.

Using the Leeds & Northrup 8078 Bridge

Technical Guide 5

For those who own a Leeds & Northrup 8078 resistance bridge, some tips on how to reduce the uncertainty in the readings.

Simple,Narrow-Band, Thermistor Thermometer

Technical Guide 10

This technical guide describes a simple circuit that provides a voltage proportional to temperature difference. The circuit is linear within 0.1 ºC over ranges of up to ±10 ºC, capable of accuracies of a few millikelvin, and will resolve temperature differences below 50 K.

Thermometer Immersion and Dry-Block Calibrators

Technical Guide 11

This technical guide provides users with a simple method for assessing the quality of thermometer immersion in dry-block calibrators. Although the test method describes the testing of dry-block calibrators, it can also be used to assess the quality of immersion in any furnace, calibration bath, oven, etc.

Making Sense of Thermocouples

Technical Guide 14

Thermocouples are the most widely used of all temperature sensors. The simplicity of two wires connected to a meter has an obvious appeal. However, when high confidence is required, thermocouples can be a liability. Unlike other temperature sensors, thermocouple faults are often not obvious and calibration of thermocouples can be a waste of time.

Correcting Radiation Thermometers for Reflection Errors

Technical Guide 15

Reflection errors occur in most practical applications of radiation thermometry. This guide describes the development of a simple graphical method (called a nomogram) for calculating reflection corrections, and gives instruction on its use.

Resistance Measurement for Thermometry

Technical Guide 18

Platinum resistance thermometers (PRT), also known as resistance-temperature detectors (RTD) and PT100 sensors (100 Ω platinum sensors), are a workhorse of both industrial and laboratory temperature measurement.

Introduction to Temperature Control

Technical Guide 20

One of the most common reasons for measuring temperature is to control it. This applies not only to industrial processes but also to many laboratory tests and experiments. To the uninitiated, control systems seem to exhibit confusing and sometimes peculiar behaviour. The purpose of this guide is to help users understand the behaviour and to obtain the best performance from temperature controllers.

Using SPRT Calibration Certificates

Technical Guide 21

Standard platinum resistance thermometer (SPRT) calibration certificates typically report measurements as resistance ratios with respect to the SPRT resistance at the triple point of water and give the uncertainties in these measured resistance ratios. This guide explains how to use the certificate with the SPRT to measure temperature, and how to calculate the uncertainty in the measured temperature caused by the calibration uncertainties.

Calibration of Low-Temperature Infrared Thermometers

Technical Guide 22

The advent of low-cost handheld infrared thermometers, which make non-contact measurements in the range –50 °C to 500 °C, has led to a proliferation of the thermometers in the food, building, and low-temperature processing industries. However, these instruments are not as simple to use as they first appear due to systematic effects related to emissivity, reflections, and the temperature of the thermometer itself. This guide explains how to calibrate low-temperature infrared thermometers and gives methods for correcting for the systematic effects.

Calibration of Low-Temperature Infrared Thermometers

Spreadsheet Download

In addition to Technical Guide 22, you can download the excel spread sheet to assist with your calculations.

Using Industrial Platinum Resistance Thermometers for Laboratory Thermometry

Technical Guide 23

Industrial platinum resistance thermometers, also known as Pt100s or RTDs, are very widely used in industry where accuracies of 1 °C or better are required. With a little care, they can also be used to obtain accuracies of 0.01 °C; this guide explains how.

Dew-Frost Error and the Chilled-Mirror Hygrometer

Technical Guide 24

Chilled mirror hygrometers provide accurate measurements of humidity as long as the state of the condensate (frost or dew) is known. Large errors are common when the mirror temperature lies between 0 °C and ‑25 °C, since the condensate can be frost or supercooled dew, or even a mixed state. This technical guide explains how to account for, and partially correct, the error in a chilled-mirror hygrometer measurement, when it is not possible to unambiguously identify the condensate.

Size-of-Source Effect in Infrared Thermometers

Technical Guide 26

The accuracy of most handheld infrared thermometers is severely limited by a phenomenon known as the size-of-source effect (SSE), which arises from scattering and diffraction of radiation within the optical system of the device. The error caused by the SSE can be many times larger than the accuracy quoted in the device's specifications. This guide explains how a calibration laboratory can characterise the SSE and provide information on a calibration certificate to enable users to correct for the SSE and achieve the best accuracy in their measurements.

Focus effect in Thermal Imagers

Technical Guide 29

Thermal imagers are being increasingly used quantitatively to make absolute temperature measurements, and thus require calibration by an accredited laboratory. However, calibration of these instruments is complicated by the fact that, for some thermal imagers, the radiometric accuracy is not retained when the focusing lens is adjusted. This impacts on the user, as the temperature readings will only be accurate if the focus setting matches that used by the calibration laboratory. This technical guide describes the origin of this focus effect, and gives advice to the calibration laboratory on how to identify whether the problem exists and what steps to take to deal with it if it does.

Emissivity of Blackbody Cavities

Technical Guide 35

Blackbodies are commonly used as a transfer medium for the calibration of radiation thermometers. While the emissivity of such cavities is generally close to 1, for high-accuracy calibrations it is important that the actual emissivity is known. This emissivity will depend on the geometry of the cavity, the emissivity of the material it is made from, and the field of view of the radiation thermometer viewing the cavity. Additionally, the emissivity will vary with any temperature non-uniformities that exist along the cavity length. Methods to calculate the cavity emissivity are highly mathematical and require sophisticated computer programs to implement them. This guide provides a brief overview on how to calculate cavity emissivity and is accompanied by a software application (Microsoft Windows compatible) that implements the method and illustrates the concepts graphically.

Emissivity of Blackbody Cavities - Software download

Technical Guide 35

In addition to the Technical Guide download providing a brief overview on how to calculate cavity emissivity, it is accompanied by a software application (Microsoft Windows compatible) that implements the method and illustrates the concepts graphically. Click Order Now to connect to our contact form and request the software for this TG.

Traceable Temperatures: An Introduction to Temperature Measurement and Calibration (2nd Ed.)

Authors: J V Nicholas and D R White

This book is a little different to most other measurement texts; it explains what goes wrong with temperature measurements, how to recognise when something is wrong, and how to fix it. Sections include operating principles, sources of error, choosing and using instruments, and calibration methods for each type of thermometer. It also provides the background material on measurement, uncertainty, calibration, accreditation, and the international measurement system, to support the understanding of the instruments and their use in making traceable temperature measurements.

Radiation Thermometry: Fundamentals and Applications in the Petrochemical Industry

Author: Peter Saunders

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.

An Introduction to Measurement Uncertainty

Authors: B D Hall and D R White

This introduction to measurement uncertainty is intended for metrology professionals working in calibration laboratories and metrology institutes, as well as students in tertiary-level science and engineering programmes. The subject matter is presented with an emphasis on developing models of the physical measurement process. The level of mathematics and statistics used is basic and is typically covered by high school studies.

GUM Tree Calculator (GTC)

The GUM Tree Calculator (GTC) is a data processing tool with full support for uncertainty calculations involving real and complex quantities.
GTC is a stand-alone executable for Windows. It can handle instructions typed at the command prompt or evaluate text files containing instructions. It is closely integrated with the Windows Explorer for ease of use and does not depend on any other software.
GTC can be used on small problems, or as a sophisticated data processing tool for more demanding tasks. Instructions use the Python programming language. An integrated development environment, with syntax highlighting and on-line help, is distributed with the calculator.

Excel add-in for Uncertainty Calculation (SGUM)

An Excel add-in available for real-valued quantities is available called SGUM.
SGUM provides a suite of worksheet functions that can be used to manipulate uncertain numbers referenced to Excel cells.
Documentation and examples are provided.
Important note about Office 2007 and 2010: The SGUM add-in was developed before the release of Office 2007. We believe that spreadsheets written with earlier Excel versions still execute correctly when opened with Excel 2007 and 2010. However, SGUM will not work properly if worksheets exceed the size limits imposed by earlier Excel versions, or use features not supported in earlier versions

R Library

An implementation of the GUM Tree method has been developed in the R data analysis language using uncertain numbers for real-valued problems.