Wind chill meter and method of measuring wind chill effect

A first thermometer is conventionally calibrated and a second is calibrated to read a predetermined temperature lower than actual temperature and provided with a heater resistor in good heat transfer relation to its bulb. Switch means connects a battery to the resistor to heat the second thermometer until it is observed to read the same as the first. Then the switch is repositioned such that appropriate circuitry causes reduced heating such that the elevated temperature condition of the second thermometer is merely "held" at that position and the bulb of the second thermometer is exposed to the wind and after a predetermined time (on the order of 30 seconds) the second thermometer is read, its reading representing the effective temperature as the result of wind chill.

The present invention relates to a meter or measuring device which will 
directly record wind chill effect or more precisely, the present apparent 
temperature due to the cooling effect of the wind. 
Numerous charts and tables have been developed to show the effect which a 
blowing wind has upon the apparent, as opposed to actual, temperature. 
Wind chill effect is included in the winter temperature forecasts by 
weather bureaus. Thermometers and other temperature measuring devices are 
not affected by the wind to the same extent that people are, and, when one 
reads a thermometer on a windy day, he is likely to feel that it is much 
colder than the thermometer indicates. For people who must work outdoors 
or sportsmen who are out in the weather, it becomes important to know the 
wind chill effective temperature to be able to avoid frostbite. However, 
very little instrumentation has been developed which is capable of 
indicating wind chill effective temperature. 
The present invention is directed to a simple and inexpensive device, which 
may be calibrated to read out effective wind chill temperature directly 
upon following certain simple instructions. More specifically, the present 
device preferably uses two spirit thermometers, a first one of which is 
calibrated conventionally, and the second one of which is calibrated so 
that it reads a lower temperature than the other. To the bulb of this 
second thermometer is cemented, or otherwise arranged so that it has good 
thermal contact, a heater element. The heater element is provided with a 
power source or other means of heating it upon demand such that when 
energized the heater causes the second thermometer to rise. When it 
reaches the temperature indication corresponding to that of the first 
thermometer, a lower rate of heating is applied equivalent to what is 
needed to simply hold the temperature without any wind effect. Means 
selectively shielding the bulb of the second thermometer while heating its 
bulb is provided. When the selective shielding is removed from the second 
thermometer, and the bulb of the second thermometer is exposed to the wind 
for a predetermined time, the second thermometer will drop in temperature 
and after a predetermined time the effective wind chill temperature can be 
read directly from the calibrations of the second thermometer. 
Not only is this meter simple and cheap to construct, it is easy to use and 
permits direct visual reading of actual and effective wind chill 
temperatures at the same time. 
Within limits, the differences in these two temperatures is proportional to 
wind velocity. Therefore, if means is provided to measure the angle of a 
line through the two thermometer levels from the horizontal, and that 
means is calibrated to show different angles in terms of wind velocity a 
simple wind velocity meter is also provided. 
More specifically, in accordance with the present invention there are 
provided first and second temperature measuring means, the first being 
conventionally calibrated and the second being calibrated in the same 
scale as the first but with that scale calibrated so that the normal 
reading is low by an amount representative of a predetermined wind chill 
effect. Heater means is associated with the second temperature measuring 
means and has appropriate energizing means so that upon energizing the 
heater means the indication of the second temperature measuring means can 
be made to correspond to that of the first temperature measuring means. 
The second temperature measuring means is selectively accessible to wind 
to effectively cool said second temperature measuring means. 
The method of the present invention uses a pair of temperature measuring 
means, the first being conventionally calibrated and the second being 
calibrated to temperature lower than the first. The second temperature 
measuring means while shielded from the wind is heated to the temperature 
where its calibration corresponds to the ambient shown in the first, at 
which point heating is reduced to a holding power. The second temperature 
measuring means is then exposed to the wind for a predetermined time. Then 
the second temperature measuring means is directly observed and the wind 
chill effect temperature is read directly from its calibrations.

A wind chill meter of the present invention is shown in a perspective view 
from the front showing the enclosing molded resinous enclosure 10 of 
generally rectangular form, which is preferably transparent so that the 
internal indicators can be seen. The enclosure 10 is a shallow box having 
a back lid closure 12. The enclosure is preferably provided with a flange 
14 provided with a hole 14a through which extends a suitable cord 16, the 
length of the cord determining whether it is suitable for placing about 
the wrist of the wearer as in the embodiment shown, or alternatively, for 
hanging the device around the wearer's neck. This cord permits necessary 
handling without worry about dropping the meter into the snow, for 
example. A longer cord permits the wearer to keep the meter tucked inside 
his jacket or coat when not in use, a recommended procedure. Within the 
casting is a thermometer mounting deck 18 which is backed with a chassis 
19 for electrical elements. This mounting deck 18 may be formed of 
insulation material or sheetmetal. The chassis 19 is preferably formed of 
a plastic insulating material, such as a phenolic. Both deck 18 and 
chassis 19 are of a size to fit snugly within casing 10. On the outside 
face of the mounting deck 18 are mounted a pair of spirit thermometers 20 
and 22 in a conventional manner for supporting thermometers on a plastic 
or sheetmetal base. The smaller thermometer 20 has conventional 
temperature calibrations. Fahrenheit calibrations 20a are shown to the 
left and Celsius calibrations 20b to the right of thermometer 20. In this 
embodiment only enlarged Fahrenheit calibrations 22a are shown for 
thermometer 22 as it is viewed through the transparent case 10 for ease in 
reading. It will be understood it may also include, or instead employ, 
only Celsius calibrations, for example. In this particular embodiment, 
thermometer 22 is larger than thermometer 20 also to aid in its reading. 
Supported on the bottom of chassis 19 and projecting above deck 18 is a 
three-position switch 24. Switch 24 is advantageously a slide switch whose 
slide is positionable by finger pressure to one of three positions as 
labeled and accessible through a slot 10a in the cover 10 which is of 
sufficient size to permit movement of the switch slide actuator. Holes 10b 
and 10c are provided in enclosure 10 opposite the bulbs of thermometers 20 
and 22, respectively, to permit free atmospheric access to the thermometer 
bulbs. Hole 10c is aligned with a hole 18a in the mounting deck and 19a in 
the chassis which, in turn, are aligned with a hole 12a (seen in FIG. 2) 
through the back panel 12, thus permitting wind passage through the 
housing through the respective aligned hole when the enclosure is turned 
to face into the wind. Holes 10c and 12a can be closed by fingers of the 
lefthand when manipulating the switch with the right, for example. 
Referring now to FIGS. 2 and 3, the back cover 12 for the enclosure is 
shown to be transparent although in a given application it may be opaque 
or backed with opaque material including operating instruction. The 
sidewalls of the enclosure 10 support the cover 12 in any appropriate way, 
as by friction fit, or hinge and latch construction. Assuming that the 
back cover 12 is transparent, it is possible to see the bottom of the 
chassis 19 which supports the switch. Conventional battery clip 28 snaps 
onto the battery 30 (advantageously a conventional 9-volt dry cell) whose 
terminals 30a and 30b are designed to be engaged and held engaging 
terminal 28a and 28b on insulating support bracket 28 so that these 
terminals are mutually insulated from one another. 
The resistors seen in FIG. 2 are selectively connected into a circuit with 
the battery 30 by a switch 24. The switch 24 is provided with terminals 
24a, 24b, 24c, and 24d which correspond to switch contacts. Terminal 24a 
is connected by a conductive lead 34 to a heater resistor 36 which is 
cemented to the bulb of thermometer 22 in a manner which will be 
described. The other end of resistor 36 is connected by a conductive lead 
38 to terminal 28a and thence terminal 30a of battery 30. Finally, 
terminal 30b of the battery is connected back through conductive lead 40 
to terminal 24b. When the switch 24 has its slide actuator positioned to 
the "set" position shown in FIG. 1, the terminals 24a and 24b are 
connected together which, in effect, connects the resistor 36 directly 
across the terminals of battery 30. As seen in FIG. 2 the resistor 36 is 
preferably a carbon resistor which has one face flattened so that the 
carbon core is in contact or near contact to the bulb of thermometer 22 to 
which it is cemented by epoxy cement or other means to assure good thermal 
contact between the heater resistor and the bulb. The heater resistor in 
this condition causes rapid heating of the thermometer causing the 
indicating temperature to rise very rapidly and in the method which will 
be described the observer compares the temperatures shown on the 
calibration on the two thermometers until they are equal. When they are 
equal, the switch 24 is set to an intermediate position which is marked 
"read" or "hold". In this position the terminals 24b and 24c are connected 
together. Since resistor 42 is connected across terminals 24c and 24a in 
this position, resistor 42 is placed in series with resistor 36 but in all 
other respects the circuit is the same. The increased resistance causes a 
reduction of current flow and, therefore, a decrease in the heating 
effect. The resistors are selected such that the heating effect produced 
on the thermometer 22 by heater resistor 36 in this circuit configuration 
is just sufficient to maintain the elevated temperature and not sufficient 
to cause its increase. When the switch 24 is positioned in the "off" 
position shown in FIG. 1 the terminals 24c and 24d are connected together 
but since 24d has no connection there is no circuit completed. In 
preferred embodiments the switch 24 has spring biasing means to urge the 
actuator out of the super-heating "set" position and into the "read" 
position in order to protect the thermometer and the meter as a whole from 
the damage due to overheating. 
In the use of the device, the following method is preferred. The switch 24 
is moved from "off" position to "set" position so that the heater 36 
causes the level of the thermometer 22 to rise. The observer reads the 
thermometers 20 and 22 and when their calibrated readings are the same, he 
repositions the switch 24 to the intermediate "read" position. In this 
position, the temperature reading of thermometer 22 is maintained over a 
short period of time, during which it does not increase or decrease so 
long as the thermometer is not exposed to the wind. To prevent 
unintentional exposure the holes 10c in the enclosure 10 and 12a in the 
back cover 12 may be covered by placing the thumb and a finger such as the 
third finger over these holes while making observations, thus, shielding 
the heater and the thermometer bulb. When the reading is to be made after 
the switch has been set in the "read" position, the thumb and finger are 
removed allowing the heater and thermometer bulb to be exposed and the 
holes 10c, 18a, and 12a are aligned in the direction of the wind. They are 
held in this position a predetermined time, for example, 30 seconds in a 
preferred embodiment, and then the level of the thermometer 22 is read 
against its calibrations which represent the effective wind chill 
temperature. 
It will be appreciated that there are numbers of variables involved and 
that small variations can make considerable differences in the results. 
The calibration of thermometer 22, for example, may vary somewhat but in a 
specific embodiment it was made such that it read 40.degree. below the 
actual temperature registered by thermometer 20 under still and unheated 
conditions. The sizes of the resistors employed may vary considerably and 
heaters, other than carbon resistors, or any other type of suitable 
resistors, can be used. The requirement, however, is that there be good 
heat transfer, and preferably conduction, between the heater element 
corresponding to heater resistor 36 and the bulb of thermometer 22. The 
requirement of resistor 42 is somewhat different because its primary use 
is not to directly heat something but rather as a current reducing means. 
This function need not be performed in exactly the circuit configuration 
shown, but whatever the current limiting function of the resistor or 
resistors employed or other devices used, the design criterion is that the 
heat produced be just sufficient to hold the selected temperature 
reasonably steady for a period of at least a minute or two under shielded 
conditions. In the embodiment shown both resistors 36 and 42 are carbon 
resistors of 100-ohm 1/2 watt size and the battery is a conventional 
9-volt dry cell. Finally, the time selected for cooling may vary somewhat 
but in the described configuration where aligned holes were sufficiently 
small to permit closing by fingertips is preferably on the order of 30 
seconds. A device built with these parameters has proved effective to 
provide a good measurement of effective wind chill temperature. 
It will be understood that the temperature indicating device can be changed 
considerably. While spirit thermometers are preferred, in other 
applications other types of thermometers, and other sizes, and 
calibrations in different scales are possible. Even use of entirely 
different types of temperature indicating devices is possible. One 
advantage of the use of thermometers, however, is that a line drawn to an 
arbitrary horizontal 44 through the levels in the two thermometers along 
the line of sight 46 provides an angle .theta. which is proportional to 
wind velocity when the wind chill effective temperature has been achieved. 
It is possible to provide slides and calibrations which can be lined up to 
give a direct reading not only of the angle but of the wind velocity 
represented by the angle in a particular piece of equipment. It is also 
possible to provide a chart which shows temperature comparison levels and 
the representative wind velocity of which they are indicative. 
For a better understanding of the present invention reference is made to 
the appended claims. These claims are intended to apply to all variations 
and modifications of structure which these terms may include. It is also 
specifically provided that a single thermometer device may be used as a 
wind chill meter for comparison against another thermometer but such an 
arrangement is not prefered in view of the inconvenience of having to find 
the thermometer corresponding to thermometer 20 in the present apparatus.