The psychrometer is a special device for measuring the temperature and humidity of the air. It consists of two thermometers: “dry” and “wet”, whose temperature sensors are completely independent of each other. The first thermometer determines the temperature while the humidity is calculated as the difference between the values of the “dry” and “wet” thermometers. There are three types of moisture meters:
Using a hydrographer to document the moisture
The temperature difference to the dry thermometer can be converted into a humidity value. The smaller the difference, the wetter the air is. It is often necessary to record ever-changing climatic conditions for a longer period of time. Especially in warehouses, museums and galleries as well as insensitive production processes the constant monitoring of these values is of great importance. That’s what the hygrograph does. The function of this device can be simplified in combination with an absorption hygrometer.
- Stationary (or stationary) psychrometer.
- Remote Control.
Stationary Psychrometer (Augusta)
The thermometers of the station psychrometers are mounted on a special stand so that the measured values of the instrument depend strongly on the speed of the airflow in the room in which the measurements are made. Among the simplest instruments of this kind, we can distinguish the hygrometer-psychrometer VIT-2, VIT-1.
If the hair expands as the moisture increases, this movement can be represented by a lever and a handle on the scale. The rotating paper drum takes the time factor – so the development of humidity for a longer period can be graphically displayed.
Modern hygrographs are equipped with quartz-controlled movements. The writing of humidity values works digitally and can be exported to storage media or computers. Most of these devices also record the temperature and easily close the measuring range from -20 to 50 degrees Celsius.
Aspiration Psychrometer (Asman)
The aspiration psychrometer is considered to be one of the most reliable gauges because its thermometers are housed in a special protective frame that protects them not only from damage but also from direct sunlight. The flow of the examined air in such a device has a constant speed of about 2 mm / s. But like the station set, the aspiration psychrometer is quite fragile, since it is built on the basis of mercury-alcohol thermometers.
Hygrostat: measures and regulates humidity reliably
Now we have learned how hygrometers work and where hygroscopes are used. The question of what is associated with hygrostat? In short, this device regulates the climatic conditions in the room. On the one hand, we can measure the humidity, on the other hand, the connected devices such as humidifiers, dehumidifiers and ventilation systems. Especially in areas where a constant atmosphere is important, hygrostats play a crucial role. The humidity setpoint is set with a rotary knob – if the measured data deviates from it, the unit emits a pulse to the air conditioner, which regulates it automatically.
Remote manometric or electronic psychrometers are industrial devices based on thermistors and resistance thermometers. For example, instead of two mercury or alcohol temperature sensors, silicon transistors.
The device and the operating principle of a psychrometer
The composition of a simple psychrometer includes two mercury or alcohol thermometers. The “wet” meter on one side is wrapped in a damp cloth, the end of which is lowered into a container of liquid. The work of a psychrometer relies on the physical property of the water to evaporate. During evaporation, the “fastest” molecules leave the liquid, causing some of the energy to be lost and the temperature of the water to drop. It is this temperature that measures the “wet” thermometer. To determine the humidity of the air with a psychrometer, you need to record the readings from two thermometers and calculate the relative humidity using the psychometric chart.
Electronic hygrostat systems are sometimes even integrated into the heating system, which enables particularly economical control. The most important fields of application of innovative hygrostats are agriculture, industry, warehouse logistics, museums and galleries – wherever stable moisture values are crucial for production and business success. But also in the private sector, such as in the warehouses, cellars, laundry rooms and dry conditions, as well as in the bathrooms, appliances reliably perform their job.
Plan climate planning professionally
High-quality models from professional suppliers are convincing due to their high measuring accuracy and long service life. We hope to inform you about the differences between individual technical devices for measuring and controlling the humidity. Individual planning is crucial for the optimal interaction of the described systems. Only when it is clear what goals are to be achieved with the help of modern technologies can experts develop an individual concept.
The absolute humidity is determined by the psychometric formula: e = EA * P (t-TC); Where:
- e is the vapor pressure in the air;
- E – an indicator of the maximum possible elasticity of steam at a temperature showing a “wet” thermometer;
- A is a coefficient. Its value depends on the device of the thermometer as well as on the velocity of the air flow near the reservoir of the thermometer;
- t is the air temperature determined by a conventional thermometer;
- P is the air pressure.
How a psychrometer works in a greenhouse
To create the right air velocity, some psychrometers in the greenhouse are attached to a handle and flung around. The principle of measuring humidity is based on the combination of two thermometers. One of them is immersed in a liquid (usually water), while the other thermometer is exposed to the air. The difference in the two temperatures makes it possible to measure moisture based on certain physical formulas, and so a psychrometer in the greenhouse is the most accurate way to obtain the desired values. Even professional weather stations work with this principle and measure the humidity.