초록 ▼

Apparatus for measuring the amount of fuel in a tank comprises a capacitive probe whose capacitance is a function of the fuel level in the tank, an electronic circuit including a monostable multivibrator to which the probe is connected as a timing capacitor and a trigger source for repetitively trig

Apparatus for measuring the amount of fuel in a tank comprises a capacitive probe whose capacitance is a function of the fuel level in the tank, an electronic circuit including a monostable multivibrator to which the probe is connected as a timing capacitor and a trigger source for repetitively triggering the monostable multivibrator to provide a series of output signals whose duty cycle is a function of probe capacitance, and a display responsive to the pulses or a signal derived from them to indicate the amount of fuel in the tank. To make the monostable output signal duty cycle directly proportional to the amount of fuel rather than to the fuel level, when the capacitance profile is not matched to the tank, the monostable duty cycle is modified before display, by transform unit (19) which provides, first, a conversion of the output signal of the multivibrator proportional to the fuel level into numerical value (20), after, a modification of said numerical value into numerical value proportional to the amount of the fuel using a look-up table stored in a read only memory (ROM) (21) and, finally, a conversion of this last-mentioned numerical value into output signal duty cycle proportional to the fuel amount in the tank (22).

대표청구항 ▼

Apparatus for measuring the amount of fuel in a fuel tank, comprising: (A) a capacitive probe disposed in a fuel tank in such a manner that the capacitance of said probe varies as a function of the level of fuel in said tank, the level of fuel in said tank being not linearly proportional to the volu

Apparatus for measuring the amount of fuel in a fuel tank, comprising: (A) a capacitive probe disposed in a fuel tank in such a manner that the capacitance of said probe varies as a function of the level of fuel in said tank, the level of fuel in said tank being not linearly proportional to the volume of fuel in said tank whereby said capacitance varies in a manner which is not linearly proportional to the volume of fuel in the tank; (B) an electronic circuit for generating an output signal indicative of the capacitance of said probe; said electronic circuit comprising; (1) a trigger source for generating trigger pulses having a predetermined frequency, said trigger pulses having a constant duty cycle; and (2) a monostable multivibrator coupled to said probe and said trigger source, said multivibrator being triggered by said trigger pulses and responding to each said trigger pulse by generating an output pulse having a duration determined by the capacitance of said probe, said output pulses defining said output signal; said multivibrator having a reset input, said multivibrator responding to the application of a pulse to its reset input by generating an output pulse having a duty cycle equal to the duty cycle of the pulse applied to its reset input; (C) transform means including a read only memory storing information relating to the amount of fuel in said tank as determined by the shape of said tank, said transform means for converting said duration of said output pulses of said output signal which is indicative of the level of fuel in said tank to a fuel volume signal having a duration which is indicative of the volume of fuel in said tank; (D) display means responsive to said fuel volume signal for displaying the amount of fuel in said tank; and (E) means for applying said trigger pulses to said reset input of said multivibrator for testing said apparatus whereby said display means applies said trigger pulses to said reset input.