Measurement and constant monitoring of air humidity is mandatory in the premises of libraries and museums. Relative humidity affects human health, storage of goods, and the functioning of various electronic devices.
Materials and tools
Relative humidity can be measured using a simple instrument called a hair or hair hygrometer. The action of this device is based on the property of human hair to lengthen with increasing humidity and shorten when it decreases. If you wish, you can make such a device yourself.
To do this, you will need:
- human hair;
- gasoline or acetone;
- hot melt glue;
- nitro glue;
- nails;
- carpentry and metalwork tools;
- drawing accessories;
- plywood sheet 5mm thick;
- thick paper;
- steel wire;
- a refill from a ballpoint pen;
- a roller with an inner diameter of about 1 cm.
In the hygrometer, you can use not only hair, but also high quality cotton thread.
Hygrometer manufacturing
Take a human hair that is at least 40 centimeters long. The hair should not be dyed and in no case covered with varnish. First of all, it must be degreased. To do this, rinse your hair in water with detergent (without conditioner) or boil it in a baking soda solution. You can also use a gasoline or acetone rinse. Attach a small plumb line at one end of the hair. It is best if the plumb line has a sharp point. To make a plumb bob, you can use the sharp end of a nail or the solvent-washed tip of a ballpoint pen. It is important that the weight of the handpiece is sufficient to straighten the vertically hanging hair. Use hot melt glue or a drop of nitro glue to secure the plumb line to the hair. Pick up a small nail and slide a piece of ballpoint pen about 5 mm long or any other suitable plastic tube over it. It is important that the tube can rotate freely and does not slip through the cap. The hygrometer is mounted on a vertical board or plywood panel with a horizontal base. Drive in a nail you have prepared with a plastic tube in the center of the vertical panel so that the hair thrown over it with its free end can be attached to the horizontal base. The part of the hair thrown over the nail was about a third of its total length. Place the hair over the nail and secure the free end with hot melt glue. With a change in humidity, the length of the hair will change, and the tip of the plumb line will rise and fall. Equip the hygrometer with a scale. It can be made from a strip of paper by sticking it to the dashboard behind the plumb line.
Hygrometer graduation
You can calibrate the hygrometer in the following way: bring the device into the bathroom, after turning on a hot shower in it. When the room begins to fill with steam, mark the lowest point on the scale, against which the plumb bob will stop, as 100%. Next, place the appliance in a heated and cooling stove oven (not very hot, so as not to burn the appliance). At the top point opposite the tip, set the 0% mark. The 50% mark can be placed in the middle between the two extreme marks. You can make a more accurate calibration with the control hygrometer, but you can also calculate it, since the scale of the hair hygrometer is linear. If you could not get a long hair and the sensitivity of the device is not enough, equip the hygrometer with an arrow. Place a small pulley over the nail instead of the plastic tube. A roller from a curtain rod for curtains, a wheel from a toy car with a tire removed, you can also make it yourself as a pulley. The main thing is that its diameter does not exceed 1 cm. In this case, the hair must be wrapped around the roller for one turn. Make the arrow from a light material: elastic wire or a strip of plastic. Glue the arrow with hot glue to the end of the roller so as not to interfere with its rotation on the spine. In this case, the hygrometer scale must be made in the form of an arc or a sector of a circle.
