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How to measure the relative humidity of the air?  Homemade hygrometer

      _cc781905-5cde-3194-bb3b-136bad5cf58d is a success in maintaining the relative humidity in the air cultivation of most orchids.

          Toda vez que a umidade relative temperature drops below 60% , our orchids no longer find ideal conditions for development, with even the most sensitive species rapidly advancing towards dehydration

         Para a medição da umidade relativa we use a device called a hygrometer. It is recommended to have one of these inside the greenhouse, but if that is not possible, you can still measure the relative humidity in a very simple way. 



1 - Method with a mercury bulb thermometer


Will need: 

- mercury bulb thermometer; 

- cotton; 

- water; 


How to make: 

You must measure the temperature in the greenhouse (write it down). Then, wrap the thermometer bulb with damp cotton and wait for 10 minutes (write down the temperature). Now you have two different temperature values, see this difference and consult the table below: 

















       For example, today it is 25 degrees, and the difference between the dry and wet bulb measurements was 4 degrees.  So, in the first row find the temperature of 25 degrees and in the first column find the difference of 4 degrees.  Connecting the line with the column, it can be concluded that the relative humidity of the air today is 70%


 2 - Hair strand method



- Straight plastic measuring 8 by 8 cm

- Scissors

- Scotch tape

- Coin ten cents

- 2 taxis

- Glue

- 3 strands of human hair, 20 cm long

- A 23 by 10 cm styrofoam base


How to do: 

  1. Cut the straight 8-by-8 cm plastic into an isosceles triangle (a triangle with two equal-sized angles) with scissors. This will serve as the gauge for your homemade hygrometer.

  2. Place the dime at the apex of the triangle and secure it with tape.

  3. Place a thumbtack that goes through the bottom of your index finger and into the base of your triangle. Make sure the indicator can  move freely around the thumbtack with your movement.

  4. Use the glue to stick the hair strands to the plastic between the thumbtack hole and the coin. These wires should be parallel to the base of the triangle.

  5. Place the indicator on its styrofoam base, about 3/4 of the way from the top of the bottom edge.

  6. Attach the thumbtack to the index finger, reaching the styrofoam base. Thread it in far enough to keep the indicator attached to the base. Make sure he can still move freely after being trapped.

  7. Place the other thumbtack on the Styrofoam base, about an inch from the top, while it remains lined up with the thumbtack holding the index finger.

  8. Pull the strands of hair tightly so that the index finger is parallel to the bottom edge of the Styrofoam base. This should make the strands perpendicular to the position of the base.

  9. Apply glue to the hair strands to attach them to the top pin. Use your scissors to trim the strands if needed.

  10. Put your hygrometer outside home. The hair strands will be longer because of the moisture in the air, allowing the indicator to point downwards; dry air will cause the strands to contract, causing the indicator to point upwards.











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