Graduation value judgment of mercurial thermometer by CCD imaging technique

For the manufacturer and metrological department, the accurate judgement of a mercurial thermometer is very important. Because of the eye's limited resolving ability, the judgement value obtained by man's eye can only reach the accuracy of about 0.1 mm graduation linewidth. Moreover, in the measurement of a mercurial thermometer's graduation value, the operator must estimate, compare, and revise each graduation value. The heavy and complicated job, and the operator's disturbance factor of fatigue and absentmindedness lead to erroneous readings. In order to increase the efficiency of measurement, this paper puts forward a method to solve the graduation value judgment of the mercurial thermometer in which the CCD imaging technique is used. This method is also advantageous to the achievement of automatic measurement of a mercurial thermometer's graduation value.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.