Electronic hydrometer and method of determining the density of a liquid

An electronic hydrometer comprising a housing having a liquid receiving chamber, means to insert a liquid of which the density is to be determined in said chamber, a float having a known weight being disposed in said chamber, a connecting shaft secured to said float and maintained axially aligned in said housing by spaced apart guide slots for guided displacement along its longitudinal axis in response to introduction of a predetermined quantity of liquid in said chamber, a sensor associated with said shaft for detecting a reference position of said shaft, a permanent magnet mounted in proximity of said shaft and having a magnetic core and a displaceable coil about said core, said coil being secured to said shaft, an electronic circuit means to automatically adjust the value of a current flowing in said coil to displace said coil and said shaft relative to said reference position, the value of said adjusted current being calibrated by said circuit to generate an output signal indicative of the density of said liquid in said chamber and a sinusoidal signal connected to said coil to impart to said shaft small oscillations whereby to prevent frictional retention of said shaft through said guide slots.