The Dimensional Metrology Group (683.01) performs calibrations of precision metal rulers. Our customers include state bureaus of Weights and Measures and departments of Agriculture. We also perform calibrations of metal rulers used in litigation by public defenders for crime scene investigations.
Precision metal rulers are calibrated by comparing the customer specified interval to a frequency-stabilized laser with active temperature, pressure and humidity corrections applied to the laser wavelength in air. Each calibration includes a NIST calibration report which provides the calibrated value and uncertainty for each specified interval.
The uncertainty in the calibrated values depends on many factors. One significant factor is the quality of the graduation marks. For metal rulers with high quality graduation marks, the expanded uncertainty U with k = 2 is U (k = 2) = (27 + 0.88L) µm where L is the length of the interval in meters.