Metrology FAQ

Frequently Asked Questions and Definitions in Metrology

What is Metrology?
Metrology is the science of measurement by definition. Measurement is the process that answers quantity questions like; how much, how cold or how fast? The determination of quantities is the business of measurement.

Much of metrological activity is geared towards ensuring that measurements are correct and the results obtained are true and reliable. Legal metrology defines what is necessary in legal terms to make a valid measurement. It also defines what a valid measurement should be.

Definition of Legal Metrology (OIML)
Legal Metrology is the entirety of the legislative, administrative and technical procedures established by, or by reference to public authorities, and implemented on their behalf in order to specify and to ensure, in a regulatory or contractual manner, the appropriate quality and credibility of measurements related to official controls, trade, health, safety and the environment.

The metrology Act of 2004 will redefine the nature of measurements in Trinidad and Tobago by:

1. Declaring the SI system as the primary system of measurement in the country while still allowing for the use of older units where required;
2. Providing for the creation of a hierarchy of National Measurement Standards;
3. Making the TTBS responsible for the administration of the Legal Metrology System;
4. Providing for the development of a cadre of Legal Metrology Inspectors to police the implementation of the bill;
5. Defining offences and punitive measures;
6. Listing the errors allowable on the measurements governed by the legislation
7. Outlining rules for the filling of pre-packaged goods.
8. Outlining methods of calibration and measurement for instruments and the contents of packages.

Why is Legal Metrology Important?
Measurements are never perfect. Flaws in the instrument, human error or environmental conditions combine to hide the detection of the quantity being measured. Metrology as a science attempts to control these negative effects to make measurements good enough for the intended purpose. Despite these imperfections all measurements are expected to be accurate and reliable. Legal metrology provides a legislative framework to provide that basic level of assurance such as;

A defined unit system

Enforced Verification/ Calibration of Measuring Instruments

Verification of the Contents of Pre-packaged goods

Provision of a set of Maximum permissible errors or tolerances for measurements of importance.

• A Defined Unit System

Definition of a system of units is an important part of the Legal Metrology process. In Trinidad and Tobago we use several unit systems at the same time and it is often unclear how a quantity should be expressed. The Act defines the International System of Units (SI) as the national unit system for Trinidad and Tobago. Traditional imperial units such as the pound are allowed but are defined in terms of SI units.

• Enforced Verification/Calibration of Instruments

Many goods are sold by quantity either in bulk or in a pre-packaged form. The instruments used to measure the quantities of bulk quantities must be verified before they are used for this purpose. How else will the customer know that the measured quantities are correct?

Under this legislation sellers using such instruments; market vendors, supermarkets, ready-mixed concrete suppliers, post offices and gas stations for example; will be required to have their equipment verified and to display the stamp or sticker to prove that this has been done. Customers can demand to see such evidence of compliance.

• Verification of the Contents of Pre-packaged goods

Goods sold in a pre-packaged form will also be considered within the law. Manufacturers will be required to ensure accurate packaging of commodities. Quantities listed on the label should be contained in the package. Goods will be checked off the shelf to ensure the compliance of filling processes.

• Tolerances and Maximum Permissible Errors

The Act recognizes that measurement like all practical human activity is not perfect. There are errors and uncertainties associated with the performance of all measurements. Tolerances and maximum permissible errors are allowed values of variation from the true value. These quantities are usually small enough to be accommodated by the activity for which they are developed. Maximum Permissible errors form part of the regulations the Act.

Who is responsible for the administration of Legal Metrology in Trinidad and Tobago?
The Trinidad and Tobago Bureau of Standards is the agency charged with the responsibility for the administration of Legal Metrology. Traditionally the Weights and Measures Inspectorate performed this function. A Legal Metrology Inspectorate will operate out of the Bureau to perform inspections and verifications.

The Bureau will also run the National Metrology Laboratory where the measurement standards of the country will be housed.

Inspections and verifications will be performed by the Legal Metrology Inspectorate. Some of the man power for this will come from the present Weights and Measures Inspectorate which is to be absorbed into the Bureau.

Policy decisions on Metrological Issues will be considered by the Metrology Advisory Committee. The make up of this committee is out lined in the legislation.

All users of measuring equipment for commercial purposes will immediately covered by the law. This is inclusive of public utilities. The scope of activity is not limited by size of the measuring unit or the type. Practical difficulties will be the only deterrent to the verification of all instruments.

When will verification activity begin?
The Metrology Bill of 2004 was originally drafted in 1974. It has taken a while to be passed. There have been many changes in the performance of measurements in that time. The regulations to accompany the Law need to reflect such changes. It is expected that verification activity will start early in 2005.

The intervening period will be spent in sensitization of the public and special interest groups. Consultations concerning large or complex measurement problems will be ongoing. Since the Law concretises the issue of conversion to the SI unit system also, it is expected that there will be many conversion issues to discuss.

How will verification work be accomplished?
Some verification work will be done at special “stations” as it has been done in the past. Verifications of installations and fixed machinery or where there are many units together will be done on site.

Two lists, one of all weighing machines and another of all service and sales providers and manufacturers of measuring equipment will be compiled by the Bureau under law. These will be used to set up verification schedules for all equipment.

Where service agents are required, they can perform their work before or alongside the verification personnel from the Bureau.

Legal Metrology Inspectors will be equipped with measurement standards that have been calibrated by the Bureau. This will ensure traceability of all measurements to the National Standards of Trinidad and Tobago. This is of course the major objective of the Metrology Act.