The use of psychrometers in the medical field has undergone a sea change. In the past, psychrometers were widely used for taking temperature and humidity readings. They are still used extensively for these purposes. However, there is a new scientific instrument that can be used in a multitude of applications. Known as a digital psychrometer, this new type of psychrometer has many exciting capabilities. Relative humidity and temperature readings can be taken with a single psychrometer instrument, a simple apparatus consisting of two evaporators and a hydrometer. The hydrometer contains a column where liquid is injected; the evaporator collects the steam. A single sling psychrometer is usually a simple, lightweight device made of stainless steel containing two thermometers connected to a small metal or plastic piece (Figures 2, 3), which is gripped by the hand. A paper strip is also wrapped around one end of the thermometer, upon which water drops (dew point) and the other end is attached to a dial. There are two types of psychrometer instruments - wet and dry. The type of measurement involved depends on the sensitivity of the device and the frequency of collection. If the measurement is not frequent enough, a wet psychrometer will probably be more effective. A dry bulb thermometer is less sensitive to variations in relative humidity and temperatures and therefore does not require a water reservoir. Most thermometers measure temperatures and relative humidity. The humidity meter is used to measure the amount of moisture present in the air, while the meter measures the temperature. Both of these instruments can also measure gasses and other molecules that could potentially be hazardous to health. These instruments are usually used in medical facilities. Reliability is another factor in choosing a particular psychrometer instrument. Relative humidity meters are considered more reliable than some other thermometers because the liquids that they collect are normally saturated with moisture before they are placed in a holding tank for analysis. The moisture level in the air is constantly changing. Relative humidity thermometers do not measure air temperatures at various temperatures because the liquids must be heated before they become a source of moisture. The instruments that are reliable to make accurate quantitative measurements are called analytical psychrometers. A hygrometer collects and measures moisture in the atmosphere using two thermometers, click for info. There is a third thermometer that is called the dispensing hygrometer. The collection and storage of moisture in the atmosphere occur when there is an increase in relative humidity. It is important to keep this information on hand so that the staff in the facility can make effective adjustments to their facilities. When selecting a hygrometer for a medical laboratory, it is important to choose a reliable instrument and has been calibrated and proven to work properly. With the many choices available in the market today, the healthcare facility staff will have a wide variety of options to select from.