How to Make a Hygrometer: 15 Steps (With Pictures)

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How to Make a Hygrometer: 15 Steps (With Pictures)
How to Make a Hygrometer: 15 Steps (With Pictures)
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A hygrometer is a device used to measure humidity or the amount of water vapor in the air. The more water vapor in the air, the higher the humidity. High humidity, which is temperature dependent, can make a hot day feel even hotter since our bodies cannot sweat as efficiently from the extra moisture in the air. You may notice that your hair becomes frizzy on a humid day. Hair expands when there is more moisture in the air. Using this principle you can create a basic hygrometer with your hair to measure relative humidity.

Steps

Method 1 of 2: Make a Hair Hygrometer

Make a Hygrometer Step 1
Make a Hygrometer Step 1

Step 1. Gather the necessary supplies

To make a hair hygrometer, you will need 2-3 pieces of hair at least 12 inches (30 cm) long, a 9 x 4-inch (23 x 10 cm) piece of wood or a piece of cardboard, two pins or nails, rubbing alcohol, a dime, tape, a marker, a sheet of clear plastic, a ruler, scissors, and a hair dryer.

  • Most of these materials should be readily available around the house.
  • If you are using nails, you will also need a hammer. Parental supervision is recommended while using the hammer.
  • You can also substitute stiff cardstock or cardboard for the transparency sheet.
Make a Hygrometer Step 2
Make a Hygrometer Step 2

Step 2. Clean hair with diluted alcohol

Mix 2 drops of alcohol and 8 drops of water. Clean hair with the mixture to remove oils or hair care products. The cleaner the hair, the more water it can absorb.

  • Keep the hair on a sheet of white paper to lose it while you build the rest of the hygrometer.
  • Clean multiple strands of hair in case one breaks during the assembly process.
Make a Hygrometer Step 3
Make a Hygrometer Step 3

Step 3. Cut out a small triangular pointer

The pointer will be the arrow that allows you to measure the relative humidity. The pointer can be made of stiff cardboard or a clear plastic sheet. Draw a triangle on the sheet that is based on 3 inches (8 cm) and the sides are about 2.5 inches (6 cm) high. Cut out the triangle using scissors.

Mark a point about 2 cm from the base of the triangle in the center. This will be the connection point for the pointer

Make a Hygrometer Step 4
Make a Hygrometer Step 4

Step 4. Tape the dime to the tip of the pointer

Using some tape, place the coin near the tip of the pointer. It is acceptable for the coin to hang slightly from the edges. The dime serves as a weight, to keep hair taut and straight.

If the tape doesn't work, you can use a little hot glue. Keep in mind that this is a slightly more permanent solution

Make a Hygrometer Step 5
Make a Hygrometer Step 5

Step 5. Glue the hair to the pointer

Glue the hair to the pointer of the hygrometer between the coin and the mark of the connection point. The hair should be perpendicular (make a 90 degree angle) to the pointer.

Make a Hygrometer Step 6
Make a Hygrometer Step 6

Step 6. Attach the pointer to the piece of wood with a pin or nail

Using the mark you made earlier, poke a hole through the pointer with a pin or nail. Hammer the pin or nail into the base of the 9 x 4 inch (23 x 10 cm) piece of wood approximately 6 ¾ inches (17 cm) from the top, with the pointer parallel to the ground (hanging horizontally).

Make sure the hole is large enough for the pointer to rotate around the nail

Make a Hygrometer Step 7
Make a Hygrometer Step 7

Step 7. Hammer a second nail into the chunk about 1 inch (2.5 cm) from the top

Measure 1 inch (3 cm) from the top of the piece on the side where the pointer is placed. Mark a point that is straight from where the hair is laid. Hammer the nail in place of the chunk. The second nail will be the anchor point for the hair.

Make a Hygrometer Step 8
Make a Hygrometer Step 8

Step 8. Glue the other end of the hair to the nail at the top of the piece

Pull the strand of hair and wrap it around the nail at the top of the piece. Add some glue to secure the hair in place. You may need to hold the hair while the glue dries to make sure it is taut.

  • Make sure the hair is tight and the tip of the pointer is horizontally straight or parallel to the ground.
  • Trim the extra hair.
Make a Hygrometer Step 9
Make a Hygrometer Step 9

Step 9. Calibrate the hygrometer

Using a dryer and a damp cloth, you can simulate zero and one hundred percent humidity conditions. Blow-dry your hair until the pointer no longer moves. Make a mark in the wood with a paint pen and label it 0 percent. This is the point where the hair does not absorb the water vapor.

  • Place the hygrometer in a sealable plastic box with a damp cloth. After 10 minutes, make a small mark with a pencil at the location of the pointer and put the hygrometer back in the box. Check back in another 10 minutes; continue this process until the pointer stops moving. Mark that point with a marker and label it 100 percent.
  • Divide the space between 0 percent and 100 percent into 10 spaces and label them 10 percent, 20 percent, 30 percent, and so on.
  • You can also calibrate the hygrometer by placing it on the bathroom counter while you shower. After marking the 100 percent line, point the dryer toward your hair until the pointer stops moving and it reads 0 percent.
Make a Hygrometer Step 10
Make a Hygrometer Step 10

Step 10. Check the position of the hygrometer pointer different times a day and record the results

Place the hygrometer on a shelf in the house or outside in an area that is protected from rain or snow. As the hair dries or absorbs the water, the pointer will move up or down to show the moisture in the air. While the measurements are not particularly accurate, they will give you an idea of the relative humidity in the air.

Method 2 of 2: Make a wet and dry hygrometer

Make a Hygrometer Step 11
Make a Hygrometer Step 11

Step 1. Gather the necessary supplies

To build this hygrometer, you will need two thermometers, some cotton gauze, an elastic band, a small container, some water, and a piece of cardboard large enough to hang the two thermometers.

Make a Hygrometer Step 12
Make a Hygrometer Step 12

Step 2. Cover a thermometer with damp gauze

Dampen the gauze with a little water and wrap it around the bulb (bottom tip) of the thermometer. Secure the gauze in place with the rubber band. For this hygrometer to work long term, the gauze must remain moist during readings.

Fill the small container with water and make sure some of the gauze is in contact with the water. The gauze will stay wet as long as it touches the water in the container

Make a Hygrometer Step 13
Make a Hygrometer Step 13

Step 3. Attach the two thermometers to the cardboard

Line up the thermometers so they are next to each other with the tops and bottoms in the same place. Secure them in place using tape or hot glue. Be careful when you use the hot glue.

Make a Hygrometer Step 14
Make a Hygrometer Step 14

Step 4. Record the temperatures on each thermometer

This hygrometer allows you to determine a relative humidity level of the air. Look at each thermometer at eye level and record the degree to which the red liquid settles. Write these temperatures.

Make multiple registrations throughout the day and also take note of the weather. It is sunny? It's raining?

Make a Hygrometer Step 15
Make a Hygrometer Step 15

Step 5. Determine the relative humidity using a wet or dry humidity table

Get a wet or dry humidity chart like the one found here. The left side of the table (y-axis) is the temperature reading from the dry thermometer. The horizontal side of the table (x-axis) is the difference between the dry and the wet thermometer.

  • Subtract the temperature of the dry thermometer from the wet thermometer (cold - dry = difference).
  • Find the temperature of the dry bulb on the vertical axis and then find the corresponding difference on the horizontal axis. You are told what the relative humidity is where these two axes meet on the graph.
  • Make sure the table matches the scale you are using. If you are going to use Fahrenheit, use a Fahrenheit table. If you are measuring in Celsius, use a Celsius table.

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