How to calculate the allowable error of bimetallic thermometer?

In industrial measurement, the accuracy grade is usually used to express the accuracy of the instrument. The accuracy grade is to remove the'+'and'%' numbers from the maximum reference error. The accuracy grade is one of the important indexes to measure the quality of the instrument.

  The accuracy grade of bimetallic thermometer is divided by the percentage of its allowable error to dial scale value. The larger the accuracy grade, the larger the allowable error to dial scale limit value. The larger the range, the greater the absolute allowable error of temperature value measured by bimetallic thermometer. The larger the absolute allowable error of 1.5 and 1.0 are respectively expressed in normal use. The allowable errors of the thermometer are (+1.5) and (+1.0) in range.