Most measuring instruments used for commercial purposes are governed by legislation aimed at promoting fair trade and protecting consumers. As a consumer, it is obviously very difficult to verify whether the 5 kilograms of potatoes you have paid for actually weighs 5 kilograms, for example. The same applies to a fuel dispenser. Did you really put 50 litres in your tank? And how can you be sure that a valid brake tester was used to check your brakes when your car was serviced?

Legislative compliance must be demonstrated by means of tests before a measuring instrument may be offered for sale on the market. This is called legal metrology. Measuring instruments may be subject to both national and international requirements.

Legal metrology

A few standard steps form the basis for enforcing requirements on measuring instruments. These principles underlying market access are briefly explained below.

 Step 1: model approval

 Step 2: initial verification

 Step 3: re-verification