The dissertation were performed on SP, Technical Institute of Sweden. The dissertation were carried out on the measurement technical department, this dissertation is a part of a bigger project, project ClampCal. One of SP’s returning assignments are flow-measurement. When flow-measurement is performed, the flow has to be stopped so that a meter can be installed in the pipes where measurement is going to take place. At every stop there is time delay in the flow which causes the customers to loose money. This is why SP wanted to find a better solution so that measurement can be done without any stops in the flow. Usage of a so-called Clamp-on meter was considered, but since the measurement uncertainty is too large it takes some investigation on the parts where the largest uncertainties occur and thus find a solution that can diminish the uncertainty as much as possible. The parts that were considered to have an opportunity to reduce measurement uncertainties were the fluid temperature, its characteristics and the pipe geometry and its characteristics. For the fluid temperature a Pt100-sensor with four different radii for various pipes was used. After calibration the sensors was tested at a test station at different temperatures and temperature stages. As expected the sensors where not as accurate as the previous sensors that was installed in the pipe, but by increasing insecurities at other parts of the measurement they can be used in this project. For the fluid characteristics a viscosity meter and a density meter was tested The viscosity meter, which was borrowed from Oleinitec, was for viscosities over 1 000, therefore it gave inaccurate results. A viscositymeter for the viscosities that occur will be purchased, but it will be delivered after the project time is over, so the necessary tests cannot be done. On the other hand the density meter gave better results than expected, the accuracy was very acceptable and it will be used in the project.