Abstract:
An apparatus for measuring water depth comprising a range discrimination circuitry and an indication circuitry. The range discrimination circuitry includes a unit pulse generator, digital counters and digital gates. The indication circuitry includes a latch circuit, BCD-to-decimal decoders and indication lamps.

Description:
This application is a continuation-in-part of my copending U.S. Patent Application Ser. No. 644,413 filed Dec. 24, 1975, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a system for measuring depth by measuring the time delay between the transmission of a high frequency sound impulse and the return of the reflected signal. 
     There are some depth measuring systems such as seen in U.S. Pat. No. 3,942,149, which may have a range portion select feature for a depth display where certain portions of depth range may be selected for finer indication. However, there is a problem with this range portion selector because when the depth is near the border between two range portions, the observer of the display must consciously determine when to change over the select switch to either of the two portions as the depth changes. 
     SUMMARY OF THE INVENTION 
     The principal object of this invention is to overcome this problem by overlapping parts of two adjacent range portions to each other, thereby eliminating the necessity of consciously noting an indication on the border line between the two range portions. 
     Another object of this invention is to provide an easily readable display. 
    
    
     BRIEF EXPLANATION OF THE DRAWINGS 
     A preferred embodiment of the present invention is described as taken together with the accompanying drawings, in which: 
     FIG. 1 is an outside view of the apparatus according to the invention; 
     FIG. 2 is a block diagram thereof; 
     FIG. 3 shows pulses at various points in the case of long range; 
     FIG. 4 is a circuit for a counter 11; 
     FIG. 5 shows waveforms of transmitted and received signals and input of a latch circuit 12; 
     FIG. 6 is a diagram for the latch circuit; 
     FIG. 7 is a logic diagram of decoders 13 and 14; 
     FIG. 8 is a network for the memory circuit; 
     FIG. 9 graphically shows the principle of selecting the short range portions; 
     FIG. 10 shows pulses at various points in the case of short range; 
     FIG. 11 is a perspective view showing part of the display unit in more detail of FIG. 1; and 
     FIG. 12 is a partial view showing another type of the range portion selector somewhat similar to FIG. 11. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in FIG. 1, the system has in its front panel 6 sixteen LEDs (light emitting diodes) 16 preferably vertically lined at regular intervals. Each of the LEDs is numbered on its one side to show every 5 meters of water depth from 0 to 75 meters for the full long or rough range scale. On the other side of the LEDs is a scale cylinder 27 which has 7 vertical groups of scale numbers corresponding to the LEDs 16 to indicate short or fine ranges, in this instance for every 1 meter, as best shown in FIG. 11. The various scale groups are assigned marks A-G, each group beginning with 0 or every 10 meters and covering 15 meters so that each group has 1 or 2 overlapped or duplicate margins of 5 meters over the neighboring groups. Cylinder 27 is turned manually with a rotary switch 25 having the alphabetical marks thereon, so that one of the number groups A-G will appear within an elongated window or slot 26 formed through panel 6 on the opposite side of the &#34;long&#34; scale across the LEDs. The long and short ranges are changed with a switch 24. 
     FIG. 12 shows a modified typed of the finer range portion select system. A front panel 6a of the display unit is provided with a preferably vertical line of LEDs 16a. Panel 6a is formed with small windows 53 at the righthand side of the top and 11th LEDs. The second to 10th LEDs are numbered serially as 1-9 between the two windows while the 12th to 16th LEDs are numbered as 1-5 below the lower window. A vertical slide member 55 has vertically lined scale numbers for every 10 meters from 0-60 at a predetermined upper portion of the slide member and 10-70 at a predetermined intermediate portion. Slide member 55 is slid up and down through a rack 56 and pinion 58 by turning a rotary switch 25a equivalent to switch 25 of FIG. 1 or 2, so that when one number of the 0-60 group appears within the top window 53, the number greater by ten than the number in the top window 53 will appear in the lower window. Thus, switching the switch 25a will provide seven range portions A-G of the &#34;short&#34; range, each range portion beginning with 0 or every 10 meters, covering 15 meters to be measured on a 1-meter scale, and having one or two margins overlapping that or those of the adjacent range portion(s). 
     Reference is made now to FIG. 2. A unit pulse oscillator (generator) 1 generates a basic reference or unit pulse during every 1.2 msec. period in which a sound wave reciprocates a unit depth of one meter through the water, as shown at (A) of FIG. 3. The time delay Δt between transmission of a sound impulse and return of the signal reflected by an underwater object a meter below the transmitter is calculated as: 
     
         Δt = 2R/v = 2R/1580 (m/s) 
    
     where R is the distance between the object and transmitter or receiver of sound impulse, and v is the speed of soundwaves in the sea water, which is 1,580 m/sec. When R is 1 meter, the time delay Δt is approximately 1.2 msec. 
     Long Range Operation: With the range switch 24 thrown toward the LONG (full) terminal, lamps 16 will be ready to indicate every 5 meters of depth. The 1-meter or 1.2-msec-period unit pulses are frequency-divided by five by a divider 2 into 5-meter or 6-msec-period pulses as shown at B of FIG. 3. These pulses are input into an AND gate 8 and are also frequency-divided in half by a 1-bit binary counter 4 into pulses C which are then divided by 8 by a 3-bit binary counter 6 into pulses D to drive a one-shot multivibrator 17. 
     Triggered b y pulses D, the multivibrator 17 produces pulses E of approximately 1.2-msec-width. A start-stop oscillator 18 generates high frequency impulses, for example of 200 kHz, to be modulated by pulse E. The modulated high frequency impulse signal F is amplified by an amplifier 19, goes through a duplexer 20 and is translated into a sound wave by a transducer 21 before being radiated through the water. FIG. 3 shows the pulses at various points of the circuitry; C&#39; and C&#34; are pulses within the 3-bit binary counter 6. The pulses D also reset a 4-bit binary counter 11 every time the sound impulse is radiated into water. 
     With the switch 24 at LONG, a voltage Vcc is applied to the AND gate 8 so that pulses B go through the AND gate 8 and an OR gate 10 to the 4-bit binary counter 11 which is well-known for hexadecimal operation. A circuit diagram of the counter 11 is shown in FIG. 4, while its B.C.D. count sequence is shown in Table 1, where the input pulses B are successively counted into pure binary codes to appear on parallel output terminals A, B, C and D and to be input into a quad latch or coincident circuit 12. The counter 11 thus provides a series of signals, each consisting of parallel outputs or bits A-D, each signal being delayed in time by pulse B from the OR gate 10. For example, if ten 5-meter pulses B (50 meters) are input into the counter, the outputs A, B, C and D will be 0, 1, 0 and 1, respectively. 
     
                                           TABLE 1__________________________________________________________________________COUNT   0 1 2 3 4 5 6 7 8 9 10                         11                           12                             13                               14                                 15__________________________________________________________________________OUTPUT A 0 1 0 1 0   0 1 0 1 0 1 0 1 0 1 B 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 C 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 D 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1__________________________________________________________________________ 
    
     
                       TABLE 2______________________________________tn             tn + 1______________________________________D               Q           .sup.-- Q1              1            00              0            1______________________________________ 
    
     The ultrasonic wave propagated by the transducer 21 is reflected by an obstacle and received by the transducer. The received signal passes though the duplexer 20 and is amplified by an amplifier 22. The amplified signal is detected by an envelope detector 23 to be an echo signal which is the input as a latch input into the quad latch 12. FIG. 5 shows the transmitted signal (a), received signal (b), amplified signal (c) and latch input (d). FIG. 6 shows a circuit diagram of the quad latch 12, while Table 2 shows the truth table. The range information from the counter 11 enters input terminals D1-4 of the latch 12, while the echo signals enter a latch input terminal CK. As the truth table shows, when the latch input is &#34;1&#34;, the D inputs are shifted or transferred to output terminals Q1-4, while when the latch input is &#34;0&#34;, the Q outputs return to the initial state (0 m.) For example, if an obstacle is 45 meters below the surface, an echo signal enters the latch input and then the ninth outputs of the counter 11 enter the input terminals D1-4 of latch 12. At this instant, the D inputs D1, D2, D3 and D4 are 1, 0, 0 and 1, respectively, which will appear on output terminals Q1-4. 
     The binary Q outputs of the quad latch are converted into a decimal signal by two BCD-to-decimal decoders 13 and 14, a logic diagram of which is shown in FIG. 7, and the truth table of which is shown in Table 3. If the Q outputs which are the input signals of decoders 13 and 14 are the ninth pulse sequence, output 9 of the decoders is &#34;1&#34;, while the other outputs are &#34;0&#34;. If there is no input into the decoders, output 0 will be &#34;1&#34;. 
     Although 16 parallel decimal outputs of a BCD-to-decimal decoder can theoretically be made with 4-bit BCD inputs, here two such decoders are used and each has 10 decimal output terminals, as practically used. 
     Since the decoders output a signal for only 6 msec, it is memorized for 300-800 msec by an analog memory 15, as shown in FIG. 8, to finally light the LED 16. 
     
                       TABLE 3______________________________________Pulse INPUTS     OUTPUTS B   D           B   A   0   1   2   3   4   5   6                    7   8     9______________________________________ 0th 0     0     0   0   1   0   0   0   0   0   0                    0   0     0                     1st                        0     0 0 1 0 1 0 0 0 0 0 0 0 0                     2nd                        0     0 1 0 0 0 1 0 0 0 0 0 0 0                     3rd                        0     0 1 1 0 0 0 1 0 0 0 0 0 0                     4th                        0     1 0 0 0 0 0 0 1 0 0 0 0 0                     5th                        0     1 0 1 0 0 0 0 0 1 0 0 0 0                     6th                        0     1 1 0 0 0 0 0 0 0 1 0 0 0                     7th                        0     1 1 1 0 0 0 0 0 0 0 1 0 0                     8th                        1     0 0 0 0 0 0 0 0 0 0 0 1 0                     9th                        1     0 0 1 0 0 0 0 0 0 0 0 0 1                    10th                        1     0 1 0 0 0 0 0 0 0 0 0 0 0                    11th                        1     0 1 1 0 0 0 0 0 0 0 0 0 0                    12th                        1     1 0 0 0 0 0 0 0 0 0 0 0 0                    13th                        1     1 0 1 0 0 0 0 0 0 0 0 0 0                    14th                        1     1 1 0 0 0 0 0 0 0 0 0 0 0                    15th                        1     1 1 1 0 0 0 0 0 0 0 0 0 0______________________________________ 
    
     Short Range Operation: FIG. 9 shows the principle of selecting the range portions for indicating depth on the one-meter scale, each portion overlapping by 5 meters the adjacent portion(s) to facilitate measurement. 
     Referring to FIGS. 1 and 2, the switch 24 is thrown into the SHORT terminal to apply voltage Vcc to an AND gate 9 into which unit pulses A and the output D of an FF (flip-flop) 7 are input. When these three inputs are all &#34;1&#34;, the AND gate output proceeds through the OR gate 10 to the 4-bit binary counter 11. 
     A BCD-to-decimal decoder 5 functions in the same way as shown in FIG. 7 and Table 3 for decoder 13 or 14, but has 3-bit binary input and decimal output signals 1-7 on output terminals A-G. As shown in FIG. 10, outputs Ma-Mg appearing on parallel terminals A-G of decoder 5 are a series of delayed pulses each rising at every 0th or 10th unit pulse and lasting for 10 unit pulses. One of the outputs M as selected by using switch 25 will set FF 7. 
     For example, if range portion B is selected, the signal Mb goes from the decoder 5 into the S (set) input terminal of FF 7. Once set with the signal Mb, FF 7 produces a pulse Kb (FIG. 10) on one output terminal to the gate 9 and a reversal pulse P on the other output terminal to reset a 4-bit binary counter 3. Thus, the moment the gate 9 is turned on by the pulse Kb, the counter 3 begins counting unit pulses A from the 10th one and produces an output signal Nb to reset FF 7 at the 25th unit pulse so that the pulse Kb will last from the 10th to 25th unit pulses. Likewise, pulse Kc will last from the 20th to 35th unit pulses. Thus, each of pulses Ka-g has one or two margins overlapping or duplicating that or those of the adjacent pulse or pulses as just shown. 
     With the switch 24 on the short terminal, pulse Kb allows the AND gate 9 to pass 16 unit pulses from the 10th and 25th into the counter 11 through the OR gate 10. 
     The functions from the counter 11 to the LEDs 16 in themselves are essentially the same between the long and the short operations. Accordingly, the short range display system as shown in FIG. 11 or 12 will indicate a 1-meter-fine depth covering 16 meters on one of the range portions A-G as selected by switch 25, each range portion having one or two margins of 5 meters overlapping that or those of the adjacent portions. 
     The observer of this depth measuring system should first measure a rough depth on the long range. He can then know which one of fine range portions A-G the measured rough depth belongs to, so that he may turn the dial 25 or 25a to select the corresponding range portion of the short range display system with scale member 27 or 55, when the switch 24 is at &#34;SHORT&#34;.