Electrical pocket thermometer with digital display

An electrical thermometer having a digital display comprises a flat, rectangular casing a principal face of which is provided with the digital indicating device, and a measuring probe which is connected with a voltage-fed electrical building block of an electronic analyzer and display unit. The thermometer is devised to be smaller and more compact than known devices and affords a safe operation even under disadvantageous environmental conditions. To this end, the voltage source of the electronic analyzer and display unit block is a solar cell arranged in a principal face of the casing. The presence of this solar cell affords a particularly advantageous permanent guarantee of the energy supply. Moreover, it offers the advantage of a construction of the thermometer casing which is free from the need for a receptacle opening for a battery and can thus be manufactured water-tight in a simple manner.

BACKGROUND OF THE INVENTION 
This invention relates to an electrical pocket thermometer with digital 
display, having a flat, rectangular casing, one of the large faces of 
which is provided with the digital display, and a measuring sensor 
(primary element) being arranged on one of the casing faces and being 
connected with a voltage-fed electrical block of electronic analyzer and 
display means. 
A known thermometer of the above-described type comprises a flat, 
rectangular casing on the frontal face of which there is arranged a 
digital display unit in the shape of a numerical LCD display. From the 
rear side of the thermometer casing there emerges a connecting lead at the 
end of which there is provided a temperature measuring probe. The 
connecting lead can be pressed, in the approximate shape of a spiral, into 
an inlay groove in the rear face of the casing, so that the measuring 
probe, which is attached to the lead end, will protrude with its probe tip 
from the casing rear wall. 
A battery shelf being closable by means of a flap is also arranged on the 
casing rear side, for receiving a voltage source for feeding current to 
the electronic analyzer and display block in the interior of the casing. 
The range of application of this known thermometer is limited because of 
the opening in the casing for receiving the battery as well as of the 
presence of a battery in general. 
OBJECTS AND SUMMARY OF THE INVENTION 
It is an object of the invention to provide a pocket thermometer of the 
above-described type which can be built smaller and more compact, and will 
permit a safe operation even under adverse environmental conditions. 
This object and others that will become apparent from the following 
description of the invention, are attained, in accordance therewith, in an 
electrical pocket thermometer of the initially described type in which the 
voltage source of the block of electronic analyzer and display means is a 
solar cell arranged in a principal face of the thermometer casing. 
Indeed it is known to operate electronic pocket devices of the most 
variegated kinds, such as pocket watches or pocket computers, with a solar 
cell arranged in a wall of their casing. Such devices are usually held in 
hand when being used and are usually not subject to particularly severe 
environmental conditions. However, the novel arrangement of a solar cell 
in a principal face, and preferably the frontal face of the thermometer 
casing which face also bears the display means, offers the advantage of 
ensuring a lasting provision of the supply of electrical energy to the 
electronically operating pocket thermometer, even at the very low 
temperatures encountered in deep freezing equipment. If a conventional 
electronically operated pocket thermometer is placed in a high performance 
deep freeze chest, the voltage supply of a conventional battery will break 
down and the thermometer will thereby become inoperative. 
Solar cells, however, work the better, the lower the ambient temperature. 
Moreover, the solar cell-equipped thermometer according to the invention 
offers the advantage that its casing can be built without a particular 
opening and recess for installing a battery therein. On the contrary the 
casing can be built, without problem, to be water-tight as well as safe 
from the danger of icing, thereby guaranteeing a long life of the 
thermometer, even when used in a freezer. 
The novel thermometer according to the invention can also be used for 
controlling the temperature of a swimming pool, or in a laboratory, for 
the temperature control of chemical baths, not to be thought of in the 
past. When the casing is sealed in hermetically in a chemically resistant 
coating which must, of course, be transparent at least in the area 
covering the display and the light-receiving face of the solar cell, then 
the thermometer can be placed without problems into the medium to be 
measured, without danger of, for instance, penetrating humidity 
detrimentally affecting electrical components of the device. The novel use 
of a solar cell in a pocket thermometer also offers the advantage of a 
substantial reduction of the volume of the casing so that, with a maximum 
degree of integration of the electrical components, it will be possible to 
give the whole device the size of a credit card. 
Thus, the casing can be blistered in a water-tight transparent foil or can 
be formed as a whole as a tight, in particular water-tight, welded-in, 
cast-in or permanently glued-in block casing, thus completely insulating 
the casing. These advantageous features are only attainable in combination 
with the novel use of a solar cell as the voltage source for the 
thermometer which permits dispensing completely with the need for a 
battery recess and openings for the introduction of electrical contactor 
means leading thereto. When the device is to be used in liquid containers 
of relatively high liquid level, such as swimming pools, then it is 
advantageous to provide the thermometer with a floating body or to design 
it as part of the same. Thus, the thermometer according to the invention 
can be mounted in or on an air-filled, inflatable floating body, in 
particular having the shape of a toy animal or a ball, at a location 
thereon where the display can be read in an easy, convenient manner. 
Thus, it is preferred in this and similar cases that the 
temperature-measuring probe or sensor (primary element) be rod-shaped and 
protrudes from the underside of the casing. This is of particular 
advantage when the thermometer is used in a swimming pool, as the 
temperature will then not be measured directly at the water surface but at 
a depth of, e.g. about 5 to 10 cm below the surface. A thermometer having 
this feature is moreover suitable for measuring the temperature in the 
interior of deformable materials, and can be used, for example, as a snow 
thermometer in the difficult determination of a ski wax the suitability of 
which depends on the temperature of the snow. An adaptation of the 
thermometer to measuring temperatures at different depths is made possible 
by the preferred feature of a measuring probe or sensor which can be 
extended or shortened due to a telescope-type structure. In this 
connection it should be noted that in particular a combination of the 
hermetically sealed thermometer casing and the rod-shaped probe protruding 
from the rear wall thereof will permit the successful measuring of the 
temperature prevailing in the interior of snow or of a liquid. A 
conventional thermometer casing provided with a battery chamber would lack 
tightness and, therefore, be susceptible to breakdown. 
When the digital display is devised as an alphanumerical display unit and 
is thus suitable for displaying also messages in word representation, then 
the thermometer according to the invention can be adapted for particularly 
specialized uses, such as, for instance, as a ski wax thermometer which 
indicates the correct wax to be used by stating a particular color, e.g., 
blue, green, silver, red and the like.

DETAILED DESCRIPTION OF THE EMBODIMENTS SHOWN IN THE DRAWING 
The thermometer 1 is a digital display pocket thermometer comprising a 
flat, rectangular casing 2 of insulating material which bears on its 
frontal face 3 a digital indicating device 4 in the form of an LCD display 
for representing the electronically determined temperature value. In one 
of the sidewalls of the casing 2, namely at its top wall 5, there is 
mounted a measuring probe 6 which is associated in a conventional manner 
(not shown) with a voltage-fed electronic analyzer and display building 
block 7 arranged in the casing 2. 
As a voltage source there is mounted in the frontal wall 3 of the casing 2 
a solar cell 8 which preferably occupies about 70 to 80% of the frontal 
face of the casing not being occupied by the indicating device 4. 
As shown in FIG. 3 the casing of the embodiment shown in FIG. 1 can be 
rendered tight, and in particular water-tight, by having it glued together 
as shown in FIG. 1 and cast in a transparent envelope free from partial 
gaps. In the embodiment shown in FIG. 2, the thermometer is completely 
enveloped by welding it into a transparent blister, thus rendering it 
likewise water- and dust-tight. In all illustrated embodiments, it is 
essential that recesses in the casing such as battery chambers and the 
like can be dispensed with which would have to be opened from time to time 
in order to exchange the batteries. This permits manufacture of the casing 
as an integral piece of truly sealed structure. 
In the embodiment shown in FIG. 1, the measuring probe 6 is connected with 
the casing by means of an external connecting cord (not shown) and this 
cord as well as the probe 6 can be clamped in grooves provided in the 
casing rear wall 10. In the embodiments of the casing shown in FIGS. 2 and 
3, the probe 6 protrudes approximately at a right angle from the casing 
rear wall 10 and is arranged at the end of a rod-shaped carrier 11 or 12, 
respectively, with the carrier 12 shown in FIG. 3 being adapted for 
telescoping to change its length. In connection with the carrier 11 or 12, 
the probe 6 thus serves, on the one hand, for measuring temperature at 
deeper levels in the interior of a medium to be measured, but, on the 
other hand, it may serve as a foot member for placing the thermometer on a 
shelf, with the solar cell advantageously in an inclined plane, facing 
obliquely upwardly under an angle most favorable for receiving incident 
light. 
In the embodiment illustrated in FIG. 2, the carrier 11 together with the 
measuring probe 6 is lodged in an elongated pocket 13 of the backside 14 
of a transparent blister 9, in order to guarantee a tight construction of 
the entire device. It can also be suitable for certain purposes, when the 
indicating device 4 is devised, on the basis of a somewhat modified 
arrangement 15 of the indicating segments, as an alpha-numerical display 
for the representation of numbers as well as words having certain 
connotations.