Barometric altimeter
First Claim
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1. A barometric altimeter comprising:
- means for generating an electrical signal Vr representing the atmospheric pressure at a reference altitude,means including a pressure sensor for generating an electrical signal Vm responsive to the atmospheric pressure at the altitude to be measured,means for generating an electrical signal v varying exponentially with time,means comparing said electrical signal v for coincidence with said electrical signals Vr and Vm for generating electrical pulses at the respective times of coincidence, tr and tm,a function generator containing a shift register loaded with a predetermined initial value, a memory storing a constant value and being non-destructively readable, a delay circuit, a complementer, first and second adders and a command pulse generator producing command pulses of a frequency determined in relation to the known characteristics of the pressure sensor, the output of said shift register being connected to one of the inputs of said first adder and also to the input of said complementer, and the output of said memory being connected to the other input of said first adder, and the output of said first adder being connected to the input of said delay circuit, and the output of said complementer being connected to one of the inputs of said second adder, and the output of said delay circuit being connected to the other input of said second adder, and the output of said second adder being connected to the input of said shift register, said function generator including means for reading out said shift register and said memory simultaneously in response to each of said command pulses in operation of said function generator,means to control the operation of said function generator to initiate operation thereof in response to the earlier generated one of said electrical pulses generated at the times tr and tm and to terminate the operation thereof in response to the later generated one of said electrical pulses generated at the times tr and tm, andsaid register, at termination of operation of said function generator, storing therein a value representative of the altitude to be measured.
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Abstract
This invention discloses apparatus for linearizing the relation between altitude and an output signal of a sensor which represents the n th power of atmospheric pressure by means of generating a basically exponential signal of a parameter and obtaining the corresponding value of the parameter at which the exponential signal coincides with the output signal of the pressure sensor. This invention also includes means for measuring an accurate altitude by correcting the above linearized value according to the standard atmosphere adopted by the ICAO by means of generating a function for compensating the effect of temperature distribution of the standard atmosphere.
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Citations
7 Claims
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1. A barometric altimeter comprising:
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means for generating an electrical signal Vr representing the atmospheric pressure at a reference altitude, means including a pressure sensor for generating an electrical signal Vm responsive to the atmospheric pressure at the altitude to be measured, means for generating an electrical signal v varying exponentially with time, means comparing said electrical signal v for coincidence with said electrical signals Vr and Vm for generating electrical pulses at the respective times of coincidence, tr and tm, a function generator containing a shift register loaded with a predetermined initial value, a memory storing a constant value and being non-destructively readable, a delay circuit, a complementer, first and second adders and a command pulse generator producing command pulses of a frequency determined in relation to the known characteristics of the pressure sensor, the output of said shift register being connected to one of the inputs of said first adder and also to the input of said complementer, and the output of said memory being connected to the other input of said first adder, and the output of said first adder being connected to the input of said delay circuit, and the output of said complementer being connected to one of the inputs of said second adder, and the output of said delay circuit being connected to the other input of said second adder, and the output of said second adder being connected to the input of said shift register, said function generator including means for reading out said shift register and said memory simultaneously in response to each of said command pulses in operation of said function generator, means to control the operation of said function generator to initiate operation thereof in response to the earlier generated one of said electrical pulses generated at the times tr and tm and to terminate the operation thereof in response to the later generated one of said electrical pulses generated at the times tr and tm, and said register, at termination of operation of said function generator, storing therein a value representative of the altitude to be measured.
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2. A barometric altimeter comprising:
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means for generating an electrical signal Vr representing the atmospheric pressure at a reference altitude, means including a pressure sensor for generating an electrical signal Vm responsive to the atmospheric pressure at the altitude to be measured, means for generating an electrical signal v varying exponentially with time, means comparing said electrical signal v for coincidence with said electrical signals Vr and Vm and for generating electrical pulses at the respective times of coincidence, tr and tm, a counting device containing first and second counter means, a comparator and first and second series-connected switches, and means for supplying a signal of predetermined frequency related to the known characteristics of the pressure sensor to said first and second series-connected switches and therethrough to said first counter means to be counted thereby, and said second counter means counting at a frequency not lower than the frequency of counting by said first counter means, and said comparator comparing a predetermined number of the most significant digits of the contents of said first and second counter means and producing first control signals when said predetermined most significant digits of said second counter means exceed said predetermined most significant digits of said first counter means, means to produce second control signals and also to reset said second counter means when the count of said second counter means reaches a predetermined value, and means to turn said second switch on in response to each of said first control signals and to turn said second switch off in response to each of said second control signals, and means to turn said first switch on in response to said electrical pulse generated at the earlier of the times tr and tm, and means to turn said first switch off in response to said electrical pulse generated at the later of the times tr and tm, and said first counter means of said counting device providing in accordance with the count thereof, the value representative of the altitude to be measured.
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3. A barometric altimeter comprising:
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means for generating an electrical signal Vr, representing the atmospheric pressure at a reference altitude, means including a pressure sensor for generating an electrical signal Vm responsive to the atmospheric pressure at the altitude to be measured, means for supplying primary command pulses, a switch connected to said supplying means, means for turning said switch on to initiate measurement of altitude, said switch, when on, passing said primary command pulses therethrough, a function generator receiving said primary command pulses passed through said switch, and in response thereto generating a function x, the value of the power series thereof being expressed by the number of said primary command pulses p received through said switch and applied to said function generator, said function generator containing m + 1 memories designated by addresses 0, 1, 2, . . . , m, where m is an integer and m ≧
2, each loaded with a predetermined intitial value, and another memory designated by address d storing a predetermined value related to the known characteristics of the pressure sensor, and a detector which detects the increment of the content of said memory of address 0 at each time a primary command pulse is applied to said function generator and produces secondary command pulses corresponding in number to said increment of the content of said memory of address 0,said function generator being operative in response to each of said primary command pulses passed through said switch and applied thereto, to add the content of said memory of address d to the content of said memory of address 0, and, in response to each of said secondary command pulses produced by said detector, to add the contents of said memories of addresses m, m-1, . . . , 2, 1 to the contents of said memories of addresses m-1, m-2, . . . , 1, 0, respectively, whereby, when p primary command pulses have passed through said switch and been applied to said function generator, the value of said function x is obtained in said memory of address, 0, and also the value x is represented by the sum of the number of said secondary command pulses, a signal generator receiving said secondary command pulses and generating in response thereto a value v varying exponentially with respect to the value of said function x, said signal generator including first and second registers loaded with a value corresponding to said signal Vr and a value proportional to said signal Vr, respectively, as initial values, a memory storing a constant value and a detector which detects the increment of the content of said first register at each time said secondary command pulse produced by said detector of said function generator is applied to said signal generator and produces tertiary command pulses corresponding in number to said increment of the content of said first register, said signal generator being operative in response to each of said secondary command pulses applied thereto to add the content of said second register to the content of said first register, and, in response to each of said tertiary command pulses produced by said detector of said signal generator, to add the content of said memory to the content of said second register, whereby the value v is obtained in said first register when x secondary command pulses have been applied to said signal generator, a comparator comparing the value v obtained in said first register of said signal generator with the value of said electrical signal Vm, and producing a coincidence signal when said value v becomes equal to said signal Vm, means to turn said switch off to stop further passage therethrough of said primary command pulses in response to said coicidence signal produced by said comparator, and a counter counting the number of primary command pulses applied to said function generator through said switch, the altitude to be measured being obtained in said counter.
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4. A barometric altimeter comprising:
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means for generating an electrical signal Vr representing the atmospheric pressure at a reference altitude, means including a pressure sensor for generating an electrical signal Vm responsive to the atmospheric pressure at the altitude to be measured, means for supplying primary command pulses, a switch connected to said supplying means, means for turning said switch on to initiate measurement of altitude, said switch, when on, passing said primary command pulses therethrough, a function generator receiving said primary command pulses passed through said switch and responsive thereto for generating a function x expressed by a logarithmic function of a variable which varies linearly with said number of primary command pulses p passed through said switch, said generator comprising first and second registers both loaded with 0 for initial values, a first memory storing a constant value which is related to the known characteristics of the pressure sensor, and a second memory storing a constant value, a detector which detects the increment of the content of said first register each time a primary command pulse is applied to said function generator and produces secondary command pulses corresponding in number to said increment of said content of said first register said function generator being operative in response to each of said primary command pulses passed through said switch and applied thereto, to add the content of said first memory to the content of said first register and to add the content of said second memory to the content of said second register, and being operative in response to each of said secondary command pulses produced by said detector, to add the content of said second register to the content of said first register, whereby, when p primary command pulses have been applied to said function generator, the value x is obtained in said first register and also the value x is represented by the sum of the number of said secondary command pulses, a signal generator for generating the value v varying exponentially with respect to the value of said function x, and comprising a shift register loaded with an initial value corresponding to said electrical signal Vr, a complementer, a delay circuit and an adder, the output of said shift register being connected to the input of said complementer and also to the input of said delay circuit, and the output of said complementer being connected to one of the inputs of said adder, and the output of said delay circuit being connected to the other input of said adder, and the output of said adder being connected to the input of said shift register, said signal generator responding to each of said secondary command pulses produced by said detector of said function generator, to read out the contents of said shift register to the inputs of said complementer and said delay circuit, and to rewrite the contents of said shift register with the output of said adder one time, whereby said value v is obtained in said shift register, a comparator comparing the value v obtained in said shift register of said signal generator with said electrical signal Vm, and producing a coincidence signal when said value v becomes equal to said signal Vm, means to turn said switch off to stop passage therethrough of said primary command pulses in response to said coincidence signal produced by said comparator, and a counter counting the number of primary command pulses applied to said function generator through said switch, the altitude to be measured being represented by the count obtained in said counter.
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5. A barometric altimeter comprising:
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means for generating an electrical voltage Vr representing the atmospheric pressure at a reference altitude, means including a pressure sensor for generating an electrical voltage Vm responsive to the atmospheric pressure at the altitude to be measured, means for generating a train of command pulses, a signal generator for generating an electrical voltage v and comprising a capacitor having a high potential terminal and a low potential terminal, means for charging said capacitor with said voltage Vr at the time of starting a measurement, a resistor, a switch, a control circuit, and a detector, one terminal of said resistor being connected to said high potential terminal of said capacitor and the other terminal of said resistor being connected to one terminal of said switch, the other terminal of said switch being connected to said low potential terminal of said capacitor, said control circuit comprising first and second registers both loaded with O at the time of start of a measurement, and a first memory storing a constant value which, in combination with the capacity of said capacitor, is related to the known characteristics of the pressure sensor, and a second memory storing a constant value, said detector detecting the increment of the content of said first register each time a command pulse is received by said control circuit and producing secondary command pulses corresponding in number to said increment of said content of said first register, and said control circuit being responsive to each command pulse of the train of command pulses applied thereto after the start of a measurement, to add the content of said first memory to the content of said first register, and to add the content of said second memory to the content of said second register, and in response to each of said secondary command pulses produced by said detector, to add the content of said second register to the content of said first register, and said switch is responsive to each of said secondary command pulses to turn on for a predetermined short time interval for discharging the electrical charge stored in said capacitor during said short time interval through said resistor and said switch, the voltage between said high potential terminal and said low potential terminal of said capacitor thereby resulting comprising said electrical voltage v, a comparator comparing said voltage Vm and said voltage v, and generating an electrical signal when coincidence thereof is detected, and a counter counting at a predetermined frequency and means for starting the counting of said counter at the start of a measurement and for stopping the counting thereby in response to said signal generated by said comparator, the count thereby obtained in said counter representing the altitude measurement.
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6. A barometric altimeter comprising:
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means for generating an electrical voltage Vr representing atmospheric pressure at a reference altitude, means including a pressure sensor for generating an electrical voltage Vm responsive to the atmospheric pressure at the altitude to be measured, a signal generator generating an electrical voltage v, and including a capacitor having a high potential terminal and a low potential terminal, means for charging said capacitor with said voltage Vr at the time of start of a measurement of altitude, an electrical network having two terminals, one of which being connected to said high potential terminal of said capacitor and the other of which being connected to said low potential terminal of said capacitor, and comprising a plurality of resistors and a plurality of switches and means for controlling said switches to provide an infinite value of resistance between said high and low potential terminals of said electrical network before the start of a measurement, and to provide a predetermined value of resistance which is related, in combination with the capacity of said capacitor, to the known characteristics of the pressure sensor at the start of a measurement and to provide a resistance value which decreases linearly with time thereafter, the voltage v being the voltage appearing between the high potential terminal and low potential terminal of said capacitor, a comparator comparing said voltage Vm and said voltage v and generating an electrical signal when coincidence is detected, and a counter counting at a predetermined frequency and means for starting the counting of said counter at the start of a measurement and for stopping the counting thereby in response to said signal generated by said comparator, the count thereby obtained in said counter representing the altitude measurement.
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7. A barometric altimeter comprising:
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means for generating an electrical signal Vr representing the atmospheric pressure at a reference altitude, means including a pressure sensor for generating an electrical signal Vm responsive to the atmospheric pressure at the altitude to be measured, means for generating an electrical signal v varying basically exponentially with time, means for comparing said electrical signal v with said electrical signals Vr and Vm and respectively producing electrical pulses at the corresponding times of coincidence therebetween, tr and tm, a function generator for generating an output function in accordance with;
##EQU18## where hm = measured altitude and hr is reference altitude, means for initiating operation of said electrical signal generating means and said function generator simultaneously to operate as a common function of time,means for controlling the operation of said function generator to initiate operation simultaneously with said electrical pulse generated at the earlier of the time tr or tm and to terminate operation in response to said electrical pulse occurring at the later of the times tr and tm, and said function generator providing a measure of the altitude in accordance with the measurement of the time elapsed between the initiation and termination of operations thereof.
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Specification