The device has a tolerance that is given to it by the Weights and Measures inspector. All devices are rejected if they are in tolerance but the average is predominately in favor of the owner or user. Dispensers are also checked to ensure that there is no diversion of flow from the hose, that the automatic shutoff is functioning properly, that the indicators are all legible and that the price is calculated properly and agrees with the advertised price. Scales Scales are checked annually for accuracy and an appropriate security seal is placed on the device to ensure they are not tampered with. The allowable error depends on the scale type being tested and the accuracy class of the scale.
Most scales found in stores are class III scales.
The scale is also tested to make sure it returns to zero after the weights are removed, that the indicating display is legible and working, and that it is level. For computing scales used in direct sales to retail customers, weight indications shall be shown on the customer's side. Price verification is conducted at least once a year on a random sample of businesses that use scanners. There are two methods for testing scanners. One method uses a hand held laser scanning unit that prints out the appropriate bar codes for each package scanned.