DHM2 Ventilation Dry-wet meter is a main instrument used to measure humidity and temperature in indoor and outdoor air. Ventilation and dry-wet meter is mainly composed of two identical mercury thermometers and a ventilator. When in use, ventilator is activated to make the ventilator inside. And the air in the ventilation duct becomes thin, so the outside air flows from the jacket of the bulb of the thermometer to the ventilation duct and the ventilator, which results in a certain speed of airflow at the bulb portion of the thermometer.
When using the DHM2 ventilated dry-wet meter, the ventilated dry-wet meter should be hung well before the observation. Where the ventilated dry-wet meter is to be suspended, the obstructions around the instrument should be at least 0.5 meters away from the thermometer bulb. This is to avoid obstacles. The thermal radiation itself affects the measured value of the thermometer. The operator should stay away from at least 0.5 meters, and approach the reading before approaching again. After the air-drying table has been hung, it must begin after a certain period of time (at least 15 minutes in summer and at least in winter. It takes 30 minutes) before observation can begin.
Before the observation, wet the wet-bulb temperature gauge's yarn cover. The time for moistening the yarn cover is 4 minutes before the observation in summer and 15 minutes before the observation in winter (when there is ice, it should be melted). The wetness shall prevail before observation. There is a phenomenon of water dripping. Wet yarn sets are made using the accessory glass of the instrument, adding water pipes, rubber sacs, and magazine clips. Wet yarn sets use distilled water and rainwater. We cannot use well water, spring water, tap water: Each time we observe, we need to re-wet once. The instrument must not be inverted when water is added.
After wetting the yarn cover, tighten the spring in the ventilator. When tightening the spring, in order to prevent the fan from rotating, use a paper stick to gently insert the air blower from the exhaust hole to stop the fan.
During work, remove the paper sticks (paper sticks can be stacked with thick paper or multiple layers of thin paper: disable hard objects, metal objects), etc. After the ventilator rotates for 4 minutes, read the thermometer and read the eye and mercury. The top of the column is horizontal, first read the decimal number, then read the integer, read the integer, and correct the reading (that is, compare with the standard temperature table listed in the two thermometers to obtain the correction value of the entire 100C point of the table, and correct , eliminate the error, and then according to the corrected dry bulb temperature and wet bulb temperature can be used in the common weather table (this instrument is attached with a concise temperature check list) to determine the absolute value of air humidity or relative value. When reading, the operator should stand downwind and the readings should be quick and accurate. After the measurement is completed, the instrument can be retracted until the fan blade stops rotating. Use in the field If the wind speed is greater than 3M/S, put a windshield on the windward surface of the ventilating and drying table ventilator. To prevent the adverse effects greater than the ventilation speed.
DHM2 ventilated dry-wet meter should be clean and non-destructive when used. Put the DHM2 ventilated dry-wet meter together on the same type of two instruments, and put it on the worktable with stable air flow. Observe after 4-6 minutes. If the contrast error temperature is greater than or equal to 1C, the humidity is less than or equal to 5%. It is judged as qualified. If the instrument has a large contrast error and the deviation is large and the deviation is very complicated, repairs should be discontinued.
The DHM2 Ventilation Dry-Wet Meter is used once every six months during the inspection cycle. The DHM2 ventilated dry-wet watch should be used in an environment free from fumes, steam and other corrosive gases. It should be hung or placed in a location away from direct sunlight. Always check that the yarn cover on the wet ball table is clean. Always pay attention to the rotation of the fan. Always check the speed of the ventilator barrel. The DHM2 ventilated dry and wet meter should be placed and carried to keep it flat and avoid violent vibration.
