Every measurement result is associated with a measurement uncertainty that is influenced by numerous factors. In addition to the measuring machine, the operator, the measuring object, and the features to be measured, the environmental conditions are a factor that is often underestimated. The temperature, in particular, has a substantial influence on measurement uncertainty. In order to take a correct measurement, both the measuring machine and the work piece must typically maintain a temperature within a few Kelvin of the reference temperature of 20 °C. The temperature must also remain constant over time and throughout the space.

Such optimal measurement conditions are often not available. Therefore, correcting temperature-induced measurement deviations is critical for many users. When measuring a distance dimension of 100 mm on a work piece made of aluminum at an ambient temperature of 25 °C, for example, the temperature-induced measurement deviations are about 7 µm. For plastics, the deviation under similar conditions can be as much as 50 µm. In extreme cases, the measurement deviations are the same order of magnitude as the tolerance on such work piece dimensions.

Automatic correction of measurement deviations resulting from differences between the ambient temperature and the reference temperature of 20 °C is standard for all Werth coordinate measuring machines. In the simplest case, the effects on the behavior of the measuring machine itself (e.g., expansion of the scale) are determined and corrected. The thermal expansion coefficient of the measuring object is treated as 11 µm / K m (a typical value for steel). This means that measuring objects and standards made of steel and materials with similar thermal expansion coefficients can be measured at a very low measurement uncertainty despite the temperature deviation. This is also helpful when performing maintenance work.

When measuring work pieces in a poorly controlled environment, a correction of the work piece temperature should also be made to compensate for the expansion coefficient of the work piece. To do so, a temperature sensor can be placed in the measurement volume, or a work piece temperature probe can be mounted directly on the measuring object. Using the thermal expansion coefficient of the work piece material, as entered by the operator, all measured lengths are corrected accordingly.

When using coordinate measuring machines in a non-climate-controlled environment, temperature correction is highly recommended, as this is the only way to effectively minimize measurement deviations.