Apparatus for the electronic-digital measurement of gas pressure

• US 3,902,355 A
• Filed: 07/17/1973
• Issued: 09/02/1975
• Est. Priority Date: 07/31/1972
• Status: Expired due to Term

• Current Assignee: Werner Weisser
• Original Assignee: Werner Weisser
• Inventors: Weisser, Werner
• Primary Examiner(s): Wood, Donald O.
• Application Number:
  US05/380,119
• Time in Patent Office: 777 Days
• Field of Search: 73/398R,398C,67.2,53,32A,384,182
• US Class Current: 73/384
• CPC Class Codes: G01L 9/0008 using vibrations

Abstract

Apparatus for measuring gas pressure to determine altitude or speed. A tuning fork is damped by the gas and its frequency is evaluated according to a hyperbolic curve consisting of two merging parts. The tuning fork is provided with rebound members to control the damping effect of the gas. Pickup is effected by electromagnetic windings or by acoustic or optical sensors. The rebound members can be sheathed by a jacket. The tuning fork can be temperature compensated. An evaluating circuit can be employed which includes a distorting portion in which a ratio-multiplier is associated with a forward-and-backward counter. The pulse input to the ratio-multiplier depends on the frequency of the tuning fork and the pulse output of the ratio-multiplier is coupled to the backward counting input of the counter, the forward counting input of which is supplied with pulses at a constant frequency. The counter has a plurality of parallel outputs.

Claims

1. An altimeter for measuring air pressure comprising an oscillator including a mechanical oscillating element surrounded by said air and whereof the frequency of oscillation is affected by the pressure of the air surrounding said oscillating element, a frequency-measuring means which measures the frequency of oscillation of the oscillator, and evaluating means which converts the measured frequency of oscillation into a value corresponding to the air pressure, said evaluating means comprising a distorting portion to which is fed an input signal whereof the frequency depends on the frequency of the oscillator, the distorting portion having a transmission characteristic curve approximating to a function by which altitude (H) depends on air pressure(p/p), so that the output signal of the distorting portion is a direct measure of the altitude (H).

2. An altimeter according to claim 1, wherein the transmission characteristic curve of the distorting portion of the circuit is made up of at least two parts of a hyperbola merging into one another.

3. An altimeter according to claim 2, wherein the distorting portion comprises a first ratio-multiplier and a first forward-and-backward counter, the ratio-multiplier having a pulse input supplied with pulses whereof the frequency depends on the frequency of the oscillator, the first ratio-multiplier having a pulse output coupled to the backward-counting input of the first forward-and-backward counter, the forward-counting input of the first forward-and-backward counter being supplied with pulses at a constant frequency, the first forward-and-backward counter having parallel outputs linked to corresponding parallel control inputs of the first ratio-multiplier, the output signal, which is a direct measure of the altitude (H), being adapted for being taken off in the form of parallel items of binary information.

4. An altimeter according to claim 3, wherein the parallel outputs of the first forward-and-backward counter are linked to a digit-indicating means and/or to a data-processing means which evaluates the altitude information or passes it on via communication paths.

5. An altimeter according to claim 3, wherein the backward-counting input of the first forward-and-backward counter is linked to the forward-counting input of a second forward-and-backward counter, the backward-counting input of the second forward-and-backward counter being linked to the pulse output of a second ratio-Multiplier, the pulse input of the second ratio-multiplier being linked to the forward-counting input of the second forward-and-backward counter, the parallel outputs of the second forward-and-backward counter being linked to the corresponding parallel control inputs of the second ratio-multiplier, the parallel outputs of the second forward-and-backward being linked to the corresponding parallel inputs of a subtraction means working in binary fashion, the parallel subtraction inputs of the subtraction means being supplied with constant binary information in parallel form, an output signal appearing on parallel outputs of the subtraction means which is a direct measure of vertical speed.

6. An altimeter according to claim 5, wherein the parallel outputs of the subtraction means are linked to a digit-indicating means and/or to a data-processing means which evaluates the vertical-speed information or passes it on via communication paths.

7. An altimeter according to claim 6, wherein the forward-counting input of the first forward-and-backward counter is linked to the pulse output of a third ratio-multiplier whereof the pulse input is supplied with pulses at a constant frequency, the parallel control inputs of the third ratio-multiplier being linked to a first change-over switch which is supplied with at least two different constant items of binary information (Mn1, Mn2) in parallel form which define the curvatures of the parts of a hyperbola which merge into one another, the output of a first OR association member being linked to the pulse input of the first ratio-multiplier, one input of the first OR association member being supplied with pulses whereof the frequency depends on the frequency of the first said oscillator, the other input of the first OR association member being linked to the pulse output of a fourth ratio-multiplier whereof the pulse input is supplied with pulses at a constant frequency, the parallel control inputs of the fourth ratio-multiplier being linked to a second change-over switch which is supplied with at least two different constant items of binary information (Ma1,Ma2) in parallel form which determine the displacement of one part of a hyperbola in the co-ordinate direction corresponding to the gas pressure with respect to the merging point of the two parts of a hyperbola, the pulse input of a fifth ratio-multiplier whereof the pulse output is linked to one input of a second OR association member being linked to the pulse input of the first ratio-multiplier, the second input of the OR association member being linked to the pulse output of the first ratio-multiplier, the output of the second OR association member being linked to the backward-counting input of the first forward-and-backward counter, the parallel control inputs of the fifth ratio-multiplier being linked to a third change-over switch which is supplied with at least two different constant items of binary information (Mb1, Mb2) in parallel form which determine the displacement of the other part of a hyperbola in the co-ordinate corresponding to altitude (H) with respect to the merging point of the two parts of a hyperbola, the first, second and third change-over switches being together linked to a change-over device, the change-over device being controlled by a frequency-discriminator, the frequency-discriminator being supplied with pulses whereof the frequency depends on the frequency of the first said oscillator, the turnover point of the discriminator lying at the frequency corresponding to the merging point of the parts of a hyperbola.