Portable diving computer

Diving computer includes a pressure sensor, a timer, a processing unit and a display screen. The processing unit processes the pressure and time data according to a given algorithm and shows on the display screen at least the data relating to how long the diver can stay at a given depth within the decompression curve. The computer is also provided with one or more mechanisms for signalling an alarm. This signalling mechanism includes a mechanism for producing permanent visual signals differentiated according to the seriousness of the errors made, which signals are controlled by the processing unit.

BACKGROUND OF THE INVENTION 
The present invention relates to diving computers. The generic term 
"computer" is used in the field of diving equipment for those kinds of 
devices that include a processing unit which uses a given algorithm to 
process the data about length of time underwater and depth, supplied, 
respectively, by a timer which is started at the beginning of the dive and 
a pressure sensor. From its calculations, the processing unit then 
produces an output consisting of how many more minutes the diver can stay 
before deviating from the decompression curve, which relates the length of 
time spent underwater to the depth. Auxiliary data are also provided, such 
as the amount of time spent underwater and the greatest depth reached. 
When the values deviate from the decompression curve, whether through some 
accidental error or a deliberate act, the so-called computer has the 
capacity to give an acoustic and/or visual signal. It is designed to 
detect dangerous situations and to respond by emitting an alarm in a large 
number of cases, as many as ten or more in the more sophisticated models. 
In addition, many computers are able to store the dive history in the 
memory of the processing unit, and even to annotate errors committed. 
However, the devices described above present the drawback of not keeping a 
sort of "list" of errors committed visible throughout the dive. The danger 
of this is that an accumulation of small errors can expose the diver to 
serious danger. Moreover, the system generally fails to discriminate 
between more serious errors and minor errors, which it reports without 
distinguishing between them 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide a computer capable of 
distinguishing more serious errors from those that are less serious, 
giving a permanent indication of both, and also calculating the 
accumulation of these errors and the effect of such accumulation on diver 
safety. 
The subject of the invention is therefore a diving computer comprising a 
pressure sensor, a timer, a processing unit and a display screen, which 
processing unit processes the pressure and time data according to a given 
algorithm and shows on the display screen at least the data relating to 
how long the diver can stay at a given depth within the decompression 
curve, said computer being provided with one or more means for signalling 
an alarm, characterized in that said visual means for signalling an alarm 
include means for producing permanent visual signals differentiated 
according to the seriousness of the errors made, which signal means are 
controlled by the processing unit. 
In particular, the control of the operation of said signal means by said 
processing unit involves comparing the errors made during the dive, 
classifying the seriousness of said errors, storing them, counting the 
errors according to their seriousness and permanently signalling the 
errors made. 
Thanks to the above features, it is possible to direct the attention of the 
diver to a number of under water behaviour errors which--per se--may not 
cause serious harms, as the formation of microbubbles or of slight 
phenomena of embolism or which simply may not be recommended to a not very 
expert diver. Therefore, the computer according to the invention performs 
what may be termed an underwater behaviour analysis, rather than simply 
the signalling of true errors, through the monitoring of not-recommended 
behaviours, even if same do not constitute serious errors. 
That is, it signals also behavior which may not be recommended to a careful 
diver. 
A second important aspect of the computer according to the invention is 
that of the illumination of the computer. Many underwater instruments may 
be illuminated. However, none of them has the possibility of a permanent 
illumination, that is an illumination during the whole time of diving 
According to the invention, the permanent illumination may be obtained 
thanks to two main factors, namely: 
1) The use of alkaline batteries, which may be easily replaced, easily 
obtained and at low costs. With three of such batteries it is possible to 
obtain about 30 hours of illumination 
2) The use of a double consent in order to avoid fortuitous illuminations 
In fact, the computer is programmed in such a manner that the illumination 
takes place in a continuous manner only if controlled through the double 
consent of two push buttons which may be operated under water .

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
FIG. 1 shows a diving computer according to the invention. The case 1 
containing the device has a display screen 2 containing the various 
displays for the values supplied by the computer, in the present case, for 
example, the dive duration display 102, the water temperature display 402, 
the depth display 302, the display 202 of greatest depth reached, the 
displays 502 and 512 of the data processed by the computer for the length 
of time permissible within the decompression curve, and the alarm signals 
602 and 612 for serious errors and minor errors respectively. The screen 
also has a light 20 controlled by the button 30, which has a lock button 
31, the two being positioned on opposite sides of the case 1; when pressed 
together, the two buttons provide continuous illumination of the display 
screen. 
Devices of this kind are normally fitted with illumination which comes on 
at the press of a button and ceases when the button is released. The 
introduction of the lock button 31 is intended to make the computer more 
convenient to use in deep water; when the button 30 is depressed a second 
time, the lock provided by the button 31 is disengaged and the 
illumination ceases. The locking action of the button 31 can be produced 
either by means of a mechanical locking action, in which case the button 
30 could provide locking means of this type itself, such as for example a 
lock screw, or by means of an electronic lighting lock circuit. Also on 
one side of the case 1 is the key 40 for controlling the functions of the 
computer. 
Shown diagrammatically in FIG. 2 is the operation of the computer according 
to the invention The computer, in a manner known per se, comprises the 
pressure sensor 3, the temperature sensor 4, the timer 5, the processing 
unit 6 and the display screen 2 which contains the displays illustrated in 
FIG. 1 and shown here in block form The sensors 3 and 4 and the timer 5 
send their data, suitably preprocessed in suitable transducers 103, 104 
and 105 respectively, both to the processing unit 6 and to the 
corresponding displays, namely to the display 102 for the timer 5, to the 
display 302 for the pressure sensor 3, which gives the depth readout in 
metres, and to the temperature value of the display 402 for the sensor 4. 
The acquired data are processed using one of the known algorithms taking 
account of a number of different standard tissues for nitrogen saturation. 
The processing unit 6 then produces the data, displayed at 502 and 512, 
which concerns, at least the remaining permissible time at the depth 
reached if the decompression curve is to be kept to. If the operations of 
the diver do not keep to safe values, the unit 6 sends a signal to the 
alarm displays 602 and 612, which may for example be two series of 
light-emitting diodes, or may equally well be liquid crystal displays 
The procedure for signalling errors is illustrated in more detail in the 
flow chart shown in FIG. 3. In the processing unit 6, the data acquired 
and processed in the step identified by the numeral 106 are compared in 
206 with the safe values; then, if the processed data derived from them 
satisfies the conditions of the decompression curve it is shown in the 
displays of the display screen 2. If however this relationship is not 
satisfied, the outputs are reexamined from the point of view of the 
seriousness of the error in 306 and also stored in the light of this 
assessment. The visual alarm signal of the two displays 602, 612 is 
permanent, and a subsequent error by the diver, with a display of the type 
illustrated diagrammatically in the Figures, will light up the next 
section of the display scale. The processing unit 6 can also add together 
two or more minor errors when their seriousness gives rise to a risk equal 
to a more serious error. 
The diving computer thus designed allows the diver to see, quickly and at 
any time, what errors have been committed, with a clear reference to their 
relative seriousness and to their cumulative seriousness.