Gravitometers

A gravitometeer comprising:

• a twin cell assembly having first and second chambers to house first and second fluids, respectively, of the same or different densities at substantially the same temperature and pressure;
• electromechanical feedback oscillator means including first and second vanes mounted in said first and second chambers, respectively, and means to oscillate both of said first and second vanes at the same or different first and second vibrational frequencies, respectively, said oscillator means having first and second output leads with first and second respective signals thereon of first and second respective frequencies directly proportional to said first and second vibrational frequencies, respectively, said first and second signals each having first and second characteristic variables, said first and second variables of said first signal being the frequency f.sub.a thereof and the period T.sub.a thereof, respectively, said first and second variables of said second signal being the frequency f.sub.g thereof and the period T.sub.g thereof, respectively;
• and computer means connected from said oscillator means output leads having an output lead means for producing an output signal thereon directly proportional to the ratio of the density of said second fluid to that of said first fluid as a function of only the second variable of one signal and at least one variable of the other signal.

A gravitometer comprising:

• a twin cell assembly having first and second chambers to house first and second fluids, respectively, of the same or different densities at substantially the same temperature and pressure;
• electromechanical feedback oscillator means including first and second vanes mounted in said first and second chambers, respectively, and driver means to oscillate both of said first and second vanes at the same or different first and second vibrational frequencies, respectively, said oscillator means having first and second output leads with first and second respective signals thereon of first and second respective frequencies directly proportional to said first and second vibrational frequencies, respectively, said first and second signals each having first and second characteristic variables, said first and second variables of said first signal being the frequency f.sub.a and the period T.sub.a thereof, respectively, said first and second variables of said second signal being the frequency f.sub.g thereof and the period T.sub.g thereof, respectively;
• and computer means connected from said oscillator means output leads having an output lead means for producing an output thereon directly proportional to the ratio of the density of said second fluid to that of said first fluid as a function of at least one of said first signal variables and at least one of said second signal variables, said oscillator means including first and second sensors having first and second output leads, respectively, to produce electrical output signals of first and second frequencies, respectively, thereon equal to the said first and second vibrational frequencies, respectively, first and second phase lock loops having first and second input leads connected from the respective first and second output leads of said sensors, said first and second phase lock loops having first and second respective output leads, said driver means being connected from said first and second phase lock loops to vibrate both of said vanes at the same or different vibrational frequencies.

A gravitometer comprising:

• a supporting body;
• first and second ferromagnetic members mounted on said body in a position to vibrate;
• a ferromagnetic driver including a coil, said electromagnetic driver being fixed relative to said body in a position to establish a magnetic field to attract both of said ferromagnetic members when said coil is energized;
• first and second devices mounted on said body to produce first and second AC electrical output signals, respectively, of first and second frequencies, respectively, of first and second frequencies of vibration of said first and second members, respectively;
• a coil input junction, said coil being connected from said coil input junction;
• and driver means connected from both of said devices to said coil input junction for impressing an AC voltage on said coil input junction to establish an AC component of current through said coil, said driver means including a source connected to said coil input junction to supply thereto a DC component of current in addition to the said AC component of current, said AC component of current modulating the intensity of said magnetic field in a manner to cause both of said ferromagnetic members to vibrate, said source causing said first and second devices to produce first and second output signals of frequencies equal to said vibrational frequencies of said first and second members, respectively, said ferromagnetic driver including said coil, said magnetic field, said ferromagnetic members, said devices, and said driver means forming a closed loop electromechanical oscillator, said driver means including an amplifier having a gain adequate to sustain vibration of both of said members continuously;
• and temperature sensitive means to vary said DC component of current in a direction such that the product
• (T.sub.g - T.sub.go)(f.sub.a - f.sub.ao)
• varies less with temperature than when said DC component of current is constant,
• T.sub.g being the period of vibration of said first member,
• T.sub.go being the vacuum period of said first member,
• f.sub.a being the vibrational frequency of said second member, and
• f.sub.ao is a constant.