quality:corruption, information:highlighting, linguistic:voice_change
Testing and certification

Most countries regulate the design and servicing of scales used for commerce. For example, in the European Union weighing instruments are subject to 2014/31/EU and 2014/32/EU directives. A conformity assessment procedure is carried out before placing the instrument on the market, andv the instruments are verified after a given period of time in member states of the European Union. This has tended to cause scale technology to lag behind other technologies because expensive regulatory hurdles are involved in introducing new designs. Nevertheless, there has been a trend to "digital load cells" which are actually strain-gauge cells with dedicated analog converters and networking built into the cell itself. Such designs have reduced the service problems inherent with combining and transmitting a number of 20 millivolt signals in hostile environments.

Government regulation generally requires periodic inspections by licensed technicians, using masses whose calibration is traceable to an approved laboratory. Scales intended for non-trade use, such as those used in bathrooms, doctor's offices, kitchens (portion control), and price estimation (but not official price determination) may be produced, but must by law be labelled "Not Legal for Trade" to ensure that they are not re-purposed in a way that jeopardizes commercial interest. In the United States, the document describing how scales must be designed, installed, and used for commercial purposes is NIST Handbook 44. Legal For Trade (LFT) certification usually approve the readability by testing repeatability of measurements to ensure a maximum margin of error of 10%.

Because gravity varies by over 0.5% over the surface of the earth, the distinction between force due to gravity and mass is relevant for accurate calibration of scales for commercial purposes. Usually, the goal is to measure the mass of the sample rather than its force due to gravity at that particular location.

Traditional mechanical balance-beam scales intrinsically measured mass. But ordinary electronic scales intrinsically measure the gravitational force between the sample and the earth, i.e. the weight of the sample, which varies with location. So such a scale has to be re-calibrated after installation, for that specific location, in order to obtain an accurate indication of mass.