An ultrasonic monitor to measure the level of a fluid (e.g., oil or water) within a
storage tank. The ultrasonic monitor is surrounded by a gas-tight, explosion-proof casing that is coupled to the top of the tank so that the acoustic axis of a (e.g., 59 KHz) ultrasonic
transducer is directed downwardly towards the surface of the fluid. The ultrasonic
transducer is encased within a protective (e.g., Delrin) housing so as to
resist the hostile (e.g., acidic, gaseous vapors and
extreme temperature) conditions within the tank. A main CPU is interconnected between the ultrasonic
transducer and an RF
transceiver having an antenna from which
fluid level data calculated by the main CPU can be transmitted over a
wireless communication path. A reference rod having at least one acoustic reflector located at a known distance therealong extends downwardly from the housing of the ultrasonic transducer towards the surface of the fluid. The main CPU is responsive to the
time of flight between incident signals generated by the acoustic transducer and return and echo signals reflected off the surface of the fluid and the acoustic reflector for calculating the corresponding distance between the fluid and the transducer. The main CPU is adapted to adjust the
time of flight to compensate for errors introduced by the environment (e.g, gas vapors, pressure, etc.) of the tank depending upon the
echo signal that is reflected to the acoustic transducer by the reflector of the reference rod.