David
What we could need is an instrument package providing us with the
following three digital readouts (using red 7-segments LED displays):
1) Ambient Temperature
2) Relative Humidity
3) Estimated Dew Point Temperature (based on the two values above)
A way to implement such a unit would be to make an electronic version of
the classic method which uses two regular thermometers, one dry and the
other kept constantly damp by means of a wet cloth wrapped around its
ball-formed base, plus some calculations to be done every time you needed
a reading.
Such an electronic version would require the use of a simple
microprocessor (to run the required calculations within a loop), two
temperature sensors (replacing the regular thermometers), the required
amount of 7-segment displays, etc, etc.
However, there is a simpler alternative for both (1) and (2) that I know
about. The ambient temperature could still be determined using a regular
thermometer, while the relative humidity could be determined using a
humidity sensor IC, i.e. the Honeywell HIH-3610 Series, ref
http://content.honeywell.com/sensing/prodinfo/humiditymoisture/009012_2.pdf
And lucky for us, there is at least one person that has already used such
a component in a homemade hygrometer device, ref
http://ludens.cl/Electron/hygro/hygro.html
So we could simply modify his version to suit our requirements and needs.
The only thing left out would be to bring a non-condensing, moisture proof
electronic hand-held calculator with us in the sub and do our dew-point
calculations by hand.
Best regards,
Jens Laland
** I have seen simple circuits that come in kit form that when inserted
** into the soil of house plants informs the user when water is needed for
** the plants...probably a small beeper.
**
** If this simple circuit were used to start a small dc fan instead (and
** work backwards of the original design in the way of activating only
** when moister is actually detected above a preset level) This fan would
** force air into a gallon bucket of moister absorbent material and this
** extra moister would be removed. Once the moister level returns to a
** better level, this fan shuts off while the moister monitoring circuit
** continues to sample for moister. This cycle would repeat itself during
** the entire duration of a dive.
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