Apparatus for use in the measurement of a variable

Apparatus for measurement of the density of a fluid within a vessel comprising a housing adapted to be mounted in the vessel and including a sealed compartment and an unsealed compartment, said unsealed compartment being open for exposure to fluid in the vessel;

• a vibratory member mounted within said unsealed compartment for exposure to fluid in the vessel;
• a first coil mounting member including a first magnetic component;
• a drive coil wound on said first magnetic component;
• drive means for applying a drive signal to said drive coil to vibrate said vibratory member at a resonant frequency representative of the density of the fluid;
• a second coil mounting member including a second magnetic component;
• a detecting coil wound on said second magnetic component and responsive to the resonant frequency, for producing a transducer output signal dependent on both the density of the fluid and the value of at least one calibration constant of said vibratory member;
• each coil mounting member being mounted in said housing adjacent said vibratory member and being formed of a material whose eddy current losses are substantially superior to those of the material of said housing, the density of said housing being substantially less than that of said coil mounting members;
• an encoder mounted within said sealed compartment, said encoder programmed with information relating to the value of the at least one calibration constant;
• and connector means mounted externally on said housing, connected to said detecting coil and said encoder, and adapted for connection to an output transducer, said connector means receiving the transducer output signal and the encoder output signal and, when connected to an output transducer, passing to the output transducer the transducer output signal and the encoder output signal and receiving from the output transducer an activating signal for application to said encoder.

Apparatus for measurement of a fluid variable within a vessel comprising a housing adapted to be mounted in the vessel and including a sealed compartment and an unsealed compartment, said unsealed compartment being open for exposure to fluid in the vessel;

• a first transducer mounted within said unsealed compartment for exposure to fluid in the vessel for producing a transducer output signal dependent on both the value of the fluid variable and the value of at least one calibration constant of the transducer;
• an encoder mounted within said sealed compartment, said encoder having a high output impedance in its inactive state, programmed with information relating to the value of the at least one calibration constant, and responsive to an activating signal for producing an encoder output signal related to the at least one calibration constant;
• and connector means mounted externally on said housing, connected to said first transducer and said encoder, and adapted for connection to an output transducer, said connector means receiving the transducer output signal and the encoder output signal and, when connected to an output transducer, passing to the output transducer the transducer output signal and the encoder output signal and receiving from the output transducer, on the same line as that on which the encoder output signal passes, an activating signal for application to said encoder, whereby the same line is utilized both for receipt by said housing of the activation signal from the output transducer and application by the housing of the encoder output signal to the output transducer.

Apparatus for measurement of the density of a fluid within a vessel comprising a housing adapted to be mounted in the vessel and including a sealed compartment and an unsealed compartment, said unsealed compartment being open for exposure to fluid in the vessel;

• a vibratory member mounted within said unsealed compartment for exposure to fluid in the vessel;
• drive means for vibrating the vibratory member at a resonant frequency representative of the density of the fluid;
• detecting means, responsive to the resonant frequency, for producing a transducer output signal dependent on both the density of the fluid and the value of at least one calibration constant of said vibratory member;
• an encoder mounted within said sealed compartment, said encoder programmed with information relating to the value of the at least one calibration constant and responsive to an activating signal for producing an encoder output signal related to the at least one calibration constant;
• connector means mounted externally on said housing and connected to said first transducer and said encoder;
• and a second transducer arranged externally of said housing, said second transducer being electrically connected to the said connector means to receive the transducer output signal and the encoder output signal, the first transducer passing to the second transducer the transducer output signal and the encoder output signal and receiving from the second transducer an activating signal for application to said encoder, the second transducer being arranged to produce an indication of the value of the variable which is substantially unaffected by the value of said at least one calibration constant.

Apparatus for measurement of the density of a fluid comprising an aircraft fuel tank for holding a fluid fuel;

• a housing at least a part of which is mounted in the fuel tank, and including a sealed compartment and an unsealed compartment, said unsealed compartment being open for exposure to fuel in the fuel tank;
• a vibratory member mounted within said unsealed compartment for exposure to fuel in the fuel tank;
• drive means for vibrating the vibratory member at a resonant frequency representative of the density of the fuel;
• detecting means, responsive to the resonant frequency, for producing a transducer output signal dependent on both the density of the fuel and the value of at least one calibration constant of said vibratory member;
• an encoder mounted within said sealed compartment, said encoder programmed with information relating to the value of the at least one calibration constant and responsive to an activating signal for producing an encoder output signal related to the at least one calibration constant;
• and connector means mounted externally on said housing, connected to said detecting means and said encoder, and adapted for connection to an output transducer, said connector means receiving the transducer output signal and the encoder output signal and, when connected to an output transducer, passing to the output transducer the transducer output signal and the encoder output signal and receiving from the output transducer an activating signal for application to said encoder.