Accuracy class

The accuracy class declared for HBM torque transducers means that the maximum of those deviations specified as percentages is equal to or less than the value declared as the accuracy class. The sensitivity tolerance is not included.

The accuracy class includes the following metrological properties explained in detail below:

• Linearity deviation including hysteresis (d_lh)
• Relative standard deviation of repeatability (σ_rel)
• Temperature effect (per 10 K) on the zero signal (TK₀)
• Temperature effect (per 10 K) on the sensitivity (TK_c)

In transducers with two or more electrical outputs (frequency output and voltage output) the output with the highest accuracy is the deciding factor in determining the accuracy class. The accuracy class must not be mistaken for classification according to DIN 51309 or EA-10/14.

Accuracy class vs. overall accuracy

The accuracy class provides practical guidance on the respective type series’ grouping within the HBM range of products. It must not be mistaken for the overall accuracy in practical use, with different individual influences acting at the same time.

Example:

We look at two versions of the T10F torque flange: on the one hand, option "S" (standard version) and on the other hand, option "G" (that is, reduced linearity deviation incl. hysteresis) in each case for the measuring ranges from 100 N·m to 10 kN·m.

In the data sheet the following maximum values are specified for the "S" version: 0.05 % for the temperature effect on the zero signal (TK₀), 0.1 % for the temperature effect on sensitivity (TK_C), and ±0.1 % for the linearity deviation incl. hysteresis (d_lh). Due to the two values given last, the accuracy class is specified as 0.1. Version "G", however, offers an improved linearity deviation incl. hysteresis (d_lh) amounting to 0.05 % only.

The temperature effect on sensitivity (TK_C) is still 0.1 % and thus is the maximum deviation among those given as percentages. Therefore, the accuracy class for version "G" still has to be specified as 0.1.

Apparently, version "G" does not provide any increased benefit. However, it shows the relatively biggest effect only with regard to one characteristic value, the TK_C. In addition, this characteristic value is the only measure for deviations related to the actual value. As a consequence, its influence is considerably smaller, for example, with measurements in the partial load range.