Make a wet bulb thermometer

[FmGrowit]

Properlymanaging the curing process and maintaining the barn can reduce fueluse drastically. No matter what type of bulk barn is used, fuelconsumption can be reduced by tightening up the barn and using awet-bulb thermometer to gauge ventilation. This wet-bulb thermometercan be made for a small amount of money . The homemade wet-bulbthermometer shown has been used successfully as an indicator ofwet-bulb temperature in bulk barns.



Materials

2 - pieces 1" PVC pipe, 7" long (one piece with1&Mac218;4" hole drilled 11&Mac218;2" from one end)
1 - piece 1" PVC pipe, 2" long
2 - 900 1" PVCelbows
2 - end caps, 1" PVC
1 - piece athleticshoestring, 7" long (wick)
1 - Tobacco curing thermometerwith bulb guards cut out
1 - wide rubber band
1 - piece ofthread (not shown) 4" long to tie wick to thermometer bulb

Instructions for Construction, Filling and Using

1.Glue all PVC pipe together as shown in figure.

2. Carefullyremove glass thermometer bulb from holder and cut out in a 1 to 11/2. square around bulb.

3. Replace glass thermometer bulband calibrate according to another thermometer.

4. Securethermometer to PVC pipe with rubber band or light gauge wire.

5.Fill with water. Use a large syringe or a small snout "squeeze-it"type plastic detergent bottle.

6. Insert wick into water. Asmall nail, large toothpick, or kitchen match stick may be helpful.

7. Place in curing barn where air flow is strong. In updraftbarns (e.g. Roanoke, Long, Powell) lay wet-bulb device flat on itsback on the perforated floor near the loading doors. In down-draftbarns (e.g. bulk tobacco), lay wet-bulb device flat on its back nearthe loading doors where air flow will strike the wet bulb of thethermometer.

8. Open fresh air vents only enough to maintaina wet-bulb temperature of 100 degrees to 105 degrees F during leafdrying and 105 degrees to 110 degrees F during stem drying.



TheUniversity of Georgia and Ft. Valley State College, the U.S.Department of Agriculture and Counties of the state cooperating. TheCooperative Extension Service offers educational programs, assistanceand materials to all people without regard to race, color, nationalorigin, age sex or disability. An Equal Opportunity/affirmativeAction Organization Committed to a Diverse Work Force.
MiscellaneousPublication ENG01-003
June 2001
Issued in furtherance ofCooperative Extension work, Acts of May 8 and June 30, 1914, TheUniversity of Georgia College of Agriculture and the U. S. Departmentof Agriculture cooperating.

Gale A. Buchanan, Dean andDirector

 

[deluxestogie]

For a 2001 article, this seems like a throwback to pre-electronic days.

Accepting the use of a wet-bulb/dry-bulb setup, the design of this is a bit odd. We just need a high-range thermometer with a wick on the bulb, and the other end of the wick dunked in a water reservoir. Here, the author builds a large inverted "U" of PVC pipe, with caps at both ends. But it seems that the only place the wick accesses water is in the bottom end cap on the right. And the only way to add water is through the tiny, drilled wick opening in the PVC pipe. The rest of the PVC pipe "U" appears to be just a picture frame for the thermometer card to tie onto.

I would suggest a short, non-inverted "U" of PVC pipe, with a removable end cap on one of the ends for easier filling. This would also provide a larger water reservoir.

[Perhaps even better would be a graph showing dry-bulb temp and RH (instead of wet-bulb temp), so a modern digital hygrometer could be used. Tables of dry vs. wet temps can be used to find the RH for the new table.]

In favor of the cited arrangement is the high cost of a digital hygrometer that can withstand 165ºF+, and that is also self-calibrating to the temperature. A simple wet-bulb can be made with a wick on a $10 metal dairy (cheesemaker's) thermometer, which goes up to 220ºF, or a compost thermometer with a 19" shaft.

Bob