On the basis of the results of calibration of current meters at water of varying temperatures, a hypothesis that water temperature influences measured water velocities was formulated. The analysis of our long-term data showed that the water temperature does have an influence on measured water velocity. This influence can be taken into account for practical purposes as a contribution to the uncertainty of measurements. The influence depends on the type of current meter propeller. This paper presents results obtained for the Ott C-2 current meter with propellers of the types 1, 2, 3, 5 and 6. Our analysis showed that the uncertainty is equal or less than 5% for measurements carried out in water with temperatures above 8°C. The differences between measured water velocities for water temperatures 5°C and 20°C reached maximum 6% (depending on the propeller) in a slowly flowing water (rotational frequency n = 1 s-1 ). For rotational velocity n ≥ 2 s-1 the differences between velocities measured at water temperatures 5 and 20°C were mostly under 3%. The less influenced propeller is of type 3 for which the uncertainty of measurement does not reach 5% even for water temperature 1ºC if the rotational frequency is bigger than 0.7 s-1 .
The paper examines in detail the influence of measurement uncertainties of the construction parameters of cemented doublet to its paraxial imaging properties. The fundamental formulas for paraxial imaging of such an optical system are presented, i.e. the optical power of the cemented doublet, the working distances of subject and image focal point, the calculation of extension amount, and then the enumeration of the transverse, angular and longitudinal magnification. All these values are affected by the uncertainties of optical system’s parameters. Therefore, the analysis of such uncertainties is carried out and derived formulas are then applied to the real example of an achromatic doublet. and Práce se podrobně zabývá analýzou vlivu nejistot měření parametrů tmeleného dubletu na jeho paraxiální zobrazovací vlastnosti. Jsou představeny základní paraxiální zobrazovací vztahy této optické soustavy, a to výpočet lámavosti dubletu, vrcholových vzdáleností předmětového a obrazového ohniska, výpočet obrazových vzdáleností vztažených k ohniskům a následně příčného, úhlového a podélného zvětšení. Nejistota parametrů optické soustavy tmeleného dubletu má vliv na tyto veličiny, vztahy odvozené rozborem nejistot jsou pak aplikovány na příkladu achromatického dubletu.