CA1304599C - Solid state accumulating altimeter - Google Patents

Abstract

Abstract of the Disclosure An altimeter device employs a solid state pressure sensor having a strain-sensitive element directly in a silicon diaphragm, which is connected at one side to a closed vacuum chamber. The entire device is very compact and may be in the form of a wristwatch. A display indicates altitude or relative altitude above or below a reference point to the user, and electronics associated with the device provide for accumulation of vertical change in one direction, regardless of intervening changes in the opposite direction. In this way, a skier, hiker or biker, for example, may determine total vertical drop or vertical rise encountered in a selected period, without regard to offset from movements in the opposite direction. At the same time, the user may also determine his altitude at any given point, and in a preferred form the altimeter device includes a clock and a time-averaging feature, for calculating and displaying rate of climb or descent, both instantaneous and average over a selected interval. The device may also have a time display, so that it functions as a wristwatch as well as an altimeter, and a synthesized voice output may be included for reporting data to the user's ear when visual observation of the display is not practical.

Description

~304599 3 SOLID STATE ACCUMULATING ALTIMETE~
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S P E C I F I C A T I O N

7 Background of the Invention 9 The invention relates to altimeters, and more particu-10 larly to a solid state altimeter device sufficiently compact 11 to be worn on the wrist and including additional features~in 12 conjunction with the altimeter function~

14 Various forms of altimeters are well Xnown, 15 particularly those for use in aircraft. Conventionally, 16 altimeters have been mechanical in nature, essentially 17 comprisin~ an atmospheric pressure-respon~ive bellows 18 connected mechanically to an indicator needle. Other 19 altimeterq have used a metal disk with strain gauges bonded 20 to the disk.

22 More recently, there have been developed special solid 23 state pressure sensors or tran~ducer~, of smaller size than 24 the conventional bellows. In these pre~sure transducers a 25 strain-sensitive element or ~train gauge has been encapsu-26 lated directly within a silicon member which acts as a 27 diaphragm. Such transducers have been used to measure 28 pressure differential between the two sides of the 29 diaphragm.
31 For example, U.S. Patent No. 4,303,903 discloses a 32 solid state pressure transducer, not forming a part of an 33 altimeter, but generally o the type smployed in the present 34 invention described below.

36 An altimeter showing the use of generally this type of 37 solid state tran~ducer is discloged in U.S. Patent No.
38 4,106,343. That altimeter, designed for aircraft use, `` 13Q4S99 , -2-included display of altitude, correction for barometric 2 pressure, and a form of rate of climb indicator consist~ing 3 of an array of LEDs.

U.S. Patent No. 4,030,065 diccloses an aircraft terrain 6 clearance warning system having an auto~atic voice warning 7 tied in with a radio altimeter.

g Piezoresistance of a semiconductor can be described as lO the change in resistance caused by an applied strain of the 11 diaphragm. Thus, solid state resistors can be used as 12 pressure sen$ors much like wire strain gauges, but with 13 several important differences and advantages.

High sensitivity, or gauge factor, in a semiconductor 16 strain gauge is perhaps lO0 times that of wire strain 17 gauges. Piezoresistors are implanted into a homogeneous 18 ~ingle cry~talline silicon medium. The implanted resistors 19 are thus part of the silicon force sensing member.

21 Prior conventional strain gauges typically were bonded 22 to members of di~similar material, re~ulting in thermo-23 elastic strain and complex fabrication processes. Mo~t 24 strain gauges are inhorently unstable duo to degradation of 25 this bond, as well as temporature sensitivity and hysteresis 26 caused by the thermo-elastic strAin.

28 Silicon is an ideal material for receiving the applied 29 differential pressure force. As a perfect crystal it does 30 not contribute to hysteresis error. After being strained, 31 it returns to the original shape.

33 Prior mechanical altimeters have been costly as 34 compared with the present invention, and yet ~till have not 35 performed all of the functions of the invention, usually 36 being limited to reporting altitude and sometimes rate of 37 climb.
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; ' ~ i "-` 1304599 Although some of the prior art included transducers or singular features relating to the present invention, none has disclosed or suggested an altimeter device of the compact design and having the advantageous features of the present invention, as described below.
Summary of the Invention In accordance with the present invention, there is provided a solid state altimeter device, comprising: an integrated circuit solid state pressure sensor including a deformable silicon diaphragm with a semiconductor strain gauge in the diaphragm; a vacuum chamber operatively attached to the diaphragm such that the vacuum of the vacuum chamber is applied to one side of the diaphragm, with the opposite side of the diaphragm exposed to atmospheric pressure; electrical means connected to the semicon-ductor strain gauge for conducting an analog signal from the strain gauge representing pressure difference between atmoæpheric and the vacuum chamber; a housing containing the pressure sensor and the vacuum chamber; microprocessor means in the housing for receiving the signal from the electrical means and for converting the signal into an altitude value; display means mounted in the housing and connected to the microprocessor means for displaying values as controlled by the microprocessor means, to a user;
calibration means connected to the microprocessor means for enabling the user to manually calibrate the altimeter device to a reference value; and accumulator means included in the micro-processor means for accumulating altitude change in one direction, ..' ~
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~3C~4599 disregarding altitude changes in the opposite direction, for a selected interval, and including an accumulation display associated with the display means for displaying said altitude change in one direction.
The solid state altimeter device of the present inven-tion is very compact and may be small enough to be wrist-worn, preferably in the form of a wristwatch. It employs a sensitive solid state pressure transducer with an attached evacuated chamber of special compact design. The device is particularly useful for skiers, hikers, and those involved in other activities wherein significant changes in altitude are encountered.
The altimeter device of the invention preferably includes an altitude accumulating feature whereby the user may set the device to accumulate vertical change in the up direction only or in the down direction only, and this is achieved by internal electronics, e.g., a microprocessor chip contained within a housing of the device.
In a preferred embodiment the altimeter device of the invention includes a time clock within the housing, and electronics for averaging altitude change with respect to time, for displaying to the user an instantaneous rate of climb or of descent. Pre-ferably, the clock also is used for standard time keeping, with the time of day displayed to the user, so that the device functions as a wristwatch as well as having the altimeter functions.
The device of the invention may perform the rate calculation by measuring the time taken to descend (or ascend) ''~''G~, - 3a --a vertical interval, such as 20 feetl and this value can be displayed as "instantaneous~' rate until the next interval's rate is calculated. The instrument can store ~ 3b -. -. --- , `

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, ` 13~4599 , -4-( 1 peak rate by calculating the rate for each vertica!l interval 2 and retaining the highest interval rate (over a user-3 selected larger interval) as the peak rate. Average rate of 4 de~cent or ascent for the user-selected interval can be 5 determined using the accumulated time over the user-selected 6 interval. For purpo~es of average rate, periods of no 7 change in altitude can be disregarded. For example, if 8 there i8 no change in altitude over a preselected time 9 period, such as lO or 15 seconds, an as~umption can be made lO that the user has qtopped for that period of time, which can 11 be omitted from the average rate calculation. Similarly, 12 inaction for this period of time can function to tell the 13 instrument the user has stoppea, triggering a display of 14 average rate.

16 The device can also include an optional stopwatch 17 function for measuring the time taken to traver~e a user-18 selected vertical interval. For example, the user might 19 enter an upper and a lower altitude value and set the device 20 to measure the time between those altitude values.
21 Alternatively, the user may trigger the stopwatch function 22 by punching a button at a start and at a stop location, and 23 thereby setting the instrument to perform the stopwatch 24 function each time the u~er passes betwen these two points, until the instrument is removed.

27 It i8 therefore among the objects of the invention to28 provide a compact, preferably wrist-worn altimeter having a 29 selectable accumulator function and preferably also a clock for determining and displaying rate of climb or descent, and 31 optionally the time of day. These and other ob~ects, advan-32 tage~, features and characteristics of the invention will be 33 apparent from the following desc~iption of a perferred 34 embodimont, considered along with the accompanying drawings.

13~4S~3 l Description of the Drawings 3 Figure l is a per~pective view showing an altimeter 4 devi~e in accordance with one e~bodi~ent of the invention, 5 in the form of a wri~twatch.

7 Figure 2 is a view 6howing a portion of the inside 8 working components of the altimeter device, including a 9 solid state pressure tran~ducer po6itioned within the 10 hou8ing of the device.

12 Figure 3 is an enlarged perspective view showing the 13 golid gtate pressure transducer.

Figure 4 iB a schematic diagram indicating generally 16 some of the circuitry asgociated with the altimeter device 17 of the invention.

19 Figure 5 is a flow chart or logic diagram relating to 20 the programming of a microprocessor included in the 21 altimeter device, for accomplishing some of the functions 22 associated with the invention.

24 Figure 6 i6 a perspective view indicating an optional 25 feature of the invention wheroin a simulated voice is gener-26 ated and conducted through earphones to the user, fo~
27 calling out desired information to the user, such as rate of 28 descent or climb without the user having to read the 29 di~play visually.
31 Figure 7 is a schematic block diagram indicating cir-32 cuitry associated with the ~imulated voice.

34 Description of Preferred Embodiments 36 In the drawings, Figure l shows an altimeter device lO
37 in accordance with the principles of the invention, shown in 38 this embodiment in the form of a wristwatch. The altimeter ., ,. ' - ' - - ~:

13C~4599 ~ -6-l device includefi a housing 11, a transparent cover~or crystal 2 12, a display 13 and manually operated buttons 14 for 3 setting and calibrating the device and for selecting deqired 4 functions.

6 Figures 2 and 3 show a solid state pressure sensor or 7 transducer included in the device, generally indicated by 8 the reference number 16. The transaucer 16 is very compact g in ~ize and shape 80 as to be contained within the housing lO ll of the device, even in the preferred form of a wrist 11 instrument as illustrated. The solid state transducer 16 12 includes a silicon diaphragm 17 within which is encapsulated 13 a strain gauge or strain responsive resistance element 18 14 who~e resistance will change with changes in flexure of the 15 diaphragm 17. The strain resistance element 18 is extremely 16 sensitive, and will indicate very accurately changes in 17 pressure differential, and the degree of changes in pressure 18 differential, between an atmospheric side l9 and a vacuum 19 side 21 of the diaphragm.

21 The silicon chip includes conductors (indicated at 22 22 and 23 in Figure 3) operably connected to the strain resis-23 tance element 18 for connection to other electronics 24 generally indicated as 24, contained within the device's 25 housing ll.

27 At the vacuum side 21 of the transducer diaphragm 17, 28 the diaphragm is connected across a closed vacuum chamber 29 26, which preferably i8 substantially evacuated (the chamber i8 shown inverted in Fig. 2). In accordance with the inven-31 tion, the chamber 26 is of a special compact design for use 32 with the compact altimeter device lO of the invention, and 33 it may be configured generally as shown in Figures 2 and 3.

Preferably, in the manufacturo of the altimeter device 36 lO, the transducer diaphragm 17 is die-attached in sealed 37 relationship to the vacuum chamber 26 in a low-pressure, 38 substantially evacuated environment. This enables the --~ 13~4S99 1 preferred configuration of chamber 26 to be used, having 2 only one open end, which mates with the diaphragm. An 3 alternative is to have a second opening in the chamber for 4 evacuation and sealing of the chamber after the diaphragm 17 5 has been attached. The vacuum can be applied to either side 6 of the diaphragm 17.

8 Electronics included in the device 10 preferably are 9 embodied in a specially designed silicon chip 25 as indi-10 cated in the drawings. The circuitry for the chip may be as 11 generally outlined in Figure 4, showing off-the-shelf inte-12 grated circuits generally available in the industry.

14 As discussed above, the altimeter device 10 of the 15 invention preferably includes a means for accumulating alti-16 tude change in one direction, irrespective of intervening 17 movement in the opposite direction. For example, a skier 18 may wish to determine the total of amount of vertical 19 deBcent traveled in one day or for a selected period, and 20 thi8 i9 made po~8ible with the device of the invention. The 21 8elector buttons 14, including buttons 14a, 14b, 14c as 22 indicated in Figure 1, enable the user of the altimeter to 23 select the desired dispiay function.

As illu~trated generally in the drawings, the display 26 13 may include a liquid crystal display or other display 27 technology for indicating altitude, accumulated altitude 28 change, or other functions as described below. One such 29 display may perform all functions, with the display function changed by the buttons 14, or several displays may be 31 included under the cover 12.

33 As shown in Figure 1, there may be included two dis-34 plays 13 and 13a, such as for displaying (on an alpha-numeric display 13) the function gelected along with (on a 36 numeric display 13a) the numerical value associated with the 37 selected unction at 13.

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- 130~599 , -8-1 There i5 preferably included within the housing 11 a 2 clock timer chip indicated at 27 in Figure 2, for providing 3 a clock function used in calculation (by the microchip 25) 4 of instantaneous rate of climb o~ descent, and also prefer-5 ably for displaying time of day to the user, on the display 6 13a.

8 The microchip 25 is a microprocessor for accompli~hing 9 the functions of the invention. The chip 25 is connected in 10 a circuit with the strain resistance element 18 and receives 11 a resistance si~nal from the strain resistance element 18 12 and a battery or batteries 29. The re~istance signal repre-13 sents the degree of strain in the element 18, xepresentative 14 of the differential pressu~e on the two sides of the trans-15 ducer diaphra~m 17. The resistance signal is an analog 16 variable signal which is converted by the microprocessor 17 chip 25 into an appropriate altitude figure.

19 Calibration of the displayed altitude, such as in 20 accordance with a known reference elevation as a starting 21 point for a skier, hiker, etc. is provided via one of the 22 buttons 14. For example, the button or switch 14c may be 23 u8ed to turn power on, which may be effective to reset a 24 "zero" 8tarting altitude at a selected location for purposes 25 of daily altitude change accumulation. Alternatively, in a 26 different embodiment a wrist instrument contemplated by the 27 invention may be programmed to display absolute altitude 28 constantly on one display, while the other display indicates 29 accumùlated vertical change. A display of absolute altitude above sea level will require a calibration, and this can be 31 accomplished by using a known altitude reference point, or 32 the system can be programmed to receive an input of baro-33 metric pressure, from which the microprocessor will deter-34 mine altitude. In such an embodiment provision is made for setting the display to read absolute altitude or barometric 36 Pre8sure.

13~)459~1 .,, 1 The buttons 14a and 14b, which may be!wide and 2 prominent on the face of the device 10 for manipulation 3 while wearing ski gloves, can be for selecting what is to be 4 displayed.

6 As indicated in Figure 2, the housing 11 includes some 7 form of vent opening 30 80 that atmospheric pressure is 8 always communicated to the outside of the transducer 9 diaphragm 17.
11 Figures 4 and 5 schematically indicate forms of circui-12 try and programming logic that may be used, in accomplishing 13 the primary objectives of a preferred embodiment of the 14 invention. These figures are intended to provide an outline 15 only and it will be appreciated by those skilled in the art 16 that any suitable form of programming may be used for the 17 microprocessor chip 27, and such programming is well within 18 the skill of the programmer.

In the flow chart of Figure 5, a preferred logic for 21 accumulating altitude change and displaying altitude, daily 22 accumulted altitude or seasonal accumulated altitude is 23 outlined.

As indicated in the initial logic entry point in Figure 26 5, the installation of a battery into the device 10 starts 27 certain operations. The battery supplies power to clear 28 number storage registers and seasonal memory, in a preferred 29 embodiment wherein a memory accumulates a daily total of altitude change in one direction, and a seasonal memory 31 (e.g., an ontire ski ~eason) accumulates over a longer 32 poriod, 34 With theso functions accomplished, the user may then i 35 turn the power on to "start" the operation of the device, 36 which is effective to clear additional registers relating to 37 daily memory. The next function of the de~ice is to measure 38 and store a first provious altitude, to be used in the h.'A, :~, .. .

13~4S9~

~ --10--1 initial altitude change calculation.

3 The decision box following indicate~ the user's ability 4 to deliberately clear ~ea~onal memory if desired at this 5 point, as an alternate method to the removal and replacement 6 of the battery as mentioned above.

8 If seasonal memory is not manually and deliberately 9 cleared at this point, the device then proceeds to measure a 10 new altitude, then to compare the new and previous altitude 11 and to calculate an altitude change. If there is no 12 altitude change, the device simply displays the function 13 that has been selected by switch positions. For example, it 14 may display altitude (relative altitude) or memory, in which 15 may be stored either the daily or the 3easonal total 16 altitude change. As indicated in Figure 5, any of these 17 three display functions can be selected by the user, as by 18 manipulation of the buttons 14 illustrated above.

If there has been an altitude change as determined by 21 the comparison of new and previous altitudes, the device 22 next determines the direction of change, i.e., up or down.
23 If the change i8 in the up direction, th$s is disregarded in 24 this preferred embodiment of the invention, which is exemplified for use by ~kiers desiring a recording of 26 accumulated altitude change in the down direction. If 27 however, the direction change is down, the device calculates 28 the altitude change, adds the amount of change to the daily 29 total, adds the amount of change to the seasonal total, and then moves the new altitude to the position of previous 31 altitude, for the purpose of the next altitude measurement 32 and comparison.

34 Logic flow continuos to display the selection as described above.

37 An optional electronic voice, which may be included to 38 call out the display function verbally to the user, is ,` --11--1 represented in the decision and function blocks in the upper 2 right of Figure 5. The signals which flow to the display 3 also are input to a voice output enable deci~ion switch, so 4 that if desired, the electronic voice will generate the 5 contents of the display audibly to the user.

7 Figure 6 shows an altimeter device lOa in another 8 embodiment of the invention, which includes the above-9 mentioned voice synthesizer feature whereby a wire pair 35 10 may be plugged into the housing lla of the device a~ indi-11 cated, leading to one or a pair of earphones 37 to be worn 12 on the head of the user. The unit lOa may be approximately 13 sized to fit in a shirt pocket of the user. The user 14 selects "voice" by manipulating a switch 38, and in this way 15 he i8 able to have certain selected information called out 16 to him at intervals or upon the touch of one of the buttons 17 14. This enables the user to obtain rate of descent infor-18 mation, for example, while he is skiing down a ski slope.
19 It enables a user to obtain any of the desired information 20 calculated by the device lOa when he is unable to conve-21 niently expose the display of the device lOa to view and 22 read the information visually.

24 Figure 7 is a block diagram representing the major 25 components for the embodiment described with reference to 26 Figure 6, including the voice synthesizer. A separate voice 27 synthesizer chip 39 may be included within the housing of 28 the device lOa. A~ is well known in the art, such a synthe-29 sizer generates the characteristics of a voice, with all 30 numbers and words needed for the desired function. A micro-31 processor chip 25a programmed to include speech memory 32 simply sends an appropriate signal to the voice synthesizer\

33 chip 39, which in turn generates a voice simulation repre-34 senting the numbers or combinations of numbers and words 35 needed to send the message through the earphones to the 36 User.

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1 The above described preferred embodiments are intended 2 to illustrate the principles of the invention, but not to 3 restrict the scope of the invention, which is defined in the 4 following claimq.
6 WE.CLAIM:

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Claims (10)

1. A solid state altimeter device, comprising:
an integrated circuit solid state pressure sensor including a deformable silicon diaphragm with a semiconductor strain gauge in the diaphragm;
a vacuum chamber operatively attached to the diaphragm such that the vacuum of the vacuum chamber is applied to one side of the diaphragm, with the opposite side of the diaphragm exposed to atmospheric pressure;
electrical means connected to the semiconductor strain gauge for conducting an analog signal from the strain gauge representing pressure difference between atmospheric and the vacuum chamber;
a housing containing the pressure sensor and the vacuum chamber;
microprocessor means in the housing for receiving the signal from the electrical means and for converting the signal into an altitude value;
display means mounted in the housing and connected to the microprocessor means for displaying values as controlled by the microprocessor means, to a user;
calibration means connected to the microprocessor means for enabling the user to manually calibrate the altimeter device to a reference value; and accumulator means included in the microprocessor means for accumulating altitude change in one direction, disregarding altitude changes in the opposite direction, for a selected interval, and including an accumulation display associated with the display means for displaying said altitude change in one direction.

2. The altimeter device of claim 1, wherein the accumulator means include means for accumulating and displaying altitude changes in the down direction and separately in the up direction, and for enabling the user to read either up or down total accumulated altitude changes.

3. The altimeter device of claim 1, further including a clock in the microprocessor means, and the microprocessor means including time averaging means for computing and displaying on the display means a rate of change in altitude over a selected interval.

4. The altimeter device of claim 3, further including rate storage means for enabling the user to cause altitude rate of change information for a selected interval to be stored and later displayed.

5. The altimeter device of claim 3, further including clock display means connected to said clock, for displaying real time to the user, whereby the device may function as an altimeter, an altitude change accumulator, a rate of altitude change indicator and a clock for the user.

6. The altimeter device of claim 5, wherein the housing comprises a generally wristwatch-sized housing with a band for retaining the device on the user's wrist.

7. The altimeter device of claim 1, wherein the housing comprises a generally wristwatch-sized housing with a band for retaining the device on the user's wrist.

8. The altimeter device of claim 7, further including a clock and a time display, whereby the device functions as an accumulating altimeter and as a wristwatch for the user.

9. The altimeter device of claim 1, further including a voice synthesizer connected to the microprocessor for generating a voice for conveying to the user information generated by the microprocessor.

10. The altimeter device of claim 1, further including an analog to digital converter in the microprocessor means, and means included in the display means for displaying the altitude as converted.