Experimental research on electrostatic voltmeters
E H W Banner · Journal of Scientific Instruments · 1927
The paper describes briefly various experimental work performed with the object of reducing the range of an electrostatic voltmeter. It was hoped to use water as the dielectric ( = 80) in order to increase the torque and so lower the full-scale voltage. The conductivity of distilled water was found to be far too high, however. Methyl alcohol ( = 34) was also tried and abandoned for the same reason. Experiments were made on a cylindrical vane-type of electrostatic voltmeter in paraffin. Under certain conditions the increase in scale for a given voltage was approximately proportional to the dielectric constant of the paraffin. Unless care is taken the mechanical properties of the liquid swamp the electrical force entirely. Another design of instrument with a constrained-strip suspension was tried and found to have its calibration directly proportional to epsilon, the mechanical effects being eliminated. The reduction of voltage for full-scale was only 1/√2 however, and hardly appreciable.