The determination of air velocity in excess of 0.5 m / s is carried out using anemometers (from the Greek. Anemos – wind). In sanitary practice, dynamic anemometers are used, based on the rotation of light blades by an air current, the revolutions of which are transmitted through a system of gears counting mechanism with a dial and an arrow. Anemometers come in two systems: cup and vane.
A cup anemometer is used for meteorological observations in a free atmosphere to determine the air velocity from 1 to 50 m / s. In the upper part of it there are four hollow hemispheres fixed on a cross, which, with the help of an axis, is in contact with a rev counter by means of a gear. Under the influence of pressure on the hemispheres of moving air, the axis rotates, each revolution is transmitted to gears, the axes of which are equipped with arrows and brought to the surface of the device. The large hand moves along the dial, which is divided into 100 parts. Each small arrow moves along the dial, divided into 10 parts, and shows values 10 times larger than the previous ones, that is, each division of the dial of the first small arrow corresponds to 100, the second to 1000.
To turn on or off the rev counter, there is a loop-lever on the side of the device.
Before starting the measurement, the large arrow is set to zero and the readings of the other two arrows are recorded. Then, having stood facing the wind and turned the dial to the researcher, the cups are allowed to rotate idle for 1-2 minutes and the rev counter is turned on. Observations are made for 10 minutes, after which the meter is turned off and the readings are recorded. The difference in the readings of the device, which shows the number of meters covered by the air flow during the observation period, is divided by the number of seconds the anemometer is working and multiplied by the correction indicated in the passport attached to the device.
meter. In hygienic practice, ball and cylinder catheters are used . The cylindrical catermometer has a scale from 35 to 38o C, and a ball – from 33 to 40o C.
Before examination, the catheter is immersed in a glass of hot water (80 ° C) and kept until alcohol fills about half of the upper dilated capillary. Then the device is wiped dry with a napkin and hung on a tripod in the center of the room at the level of 1.5 meters from the floor. When working near heat sources or in the presence of solar radiation, the catheter must be protected from the action of radiant energy; any screen (cardboard, plywood) painted in white is used for this. Using a stopwatch, the time in seconds is noted, during which the catheter cools from temperature t 1 to t 2 . The temperature intervals are chosen such that the half-sum of the upper and lower values is 36.5 ° C. Therefore, when using a ball catheter, monitoring of cooling can be carried out in the intervals of 40–33 ° C, 39–34 ° C, 38–35 ° C.
The value of the cooling ability of air when observed within the range of 38–35 ° C is determined by the formula:
H = F / a
where H is the desired value of cooling in milliliters from 1 cm 2 the surface of the catheter meter tank for 1 second;
F is the catheter meter factor, a constant value, showing the amount of heat lost from 1 cm 2 of the surface of this device (indicated on the back of the device);
and – instrument cooling time (in seconds).
When observing the cooling of a ball catheter in other intervals (40–33 ° C, 39–34 ° C), the value of the cooling ability H is calculated by the formula :
H = Ф * (t 1 –t 2 ) / a
where Ф is the constant of the catheter meter, showing the amount of heat in milliories, lost from 1 cm 2 of the surface of the tank when the temperature drops by 1 ° С. Ф = F / 3.