DENSITOMETER AND PROBE THEREFOR

A vibration densitometer comprising an electromechanical oscillator including a probe having a thin vane that is vibrated while submerged in a fluid by a magnetostrictive driver. A piezoelectric crystal mounted on the vane puts out an A.C. signal of a frequency equal to the resonant frequency of the vane, the oscillator feedback loop including an amplifier which feeds the driver coil with a signal having an A.C. component of a frequency Af/2 where A is one of the numbers 1 and 2. The loop provides an output signal of a frequency directly proportional to f which is fed to a linearization circuit that produces an output signal directly proportional to the density of the fluid. The linearization circuit output signal is then impressed upon an indicator which, if desired, may be calibrated to read in density, which density is directly proportional to the magnitude of the linearization circuit output signal. The driver includes a magnetostrictive tube that is held in compression to vibrate the vane. The tube is held in compression by a Belleville spring. The spring provides at least four outstanding advantages. It decreases start-up time. It increases accuracy. It provides temperature compensation. It makes possible the use of a more durable housing metal.