How does an electronic hygrometer work? Which is the right electronic hygrometer or mechanical hygro

How does an electronic hygrometer work?

Because the temperature sensing bubble of the wet bubble thermometer is wrapped in cotton yarn, the lower end of the cotton yarn is immersed in water, and the temperature indication of the wet bubble thermometer is always lower than the temperature indicator (air temperature) of the dry bubble thermometer due to the evaporation of the water.

Absolute Humidity vs. Relative Humidity:

Absolute humidity: The pressure p of the water vapor in the air is called the absolute humidity of the air

The humidity of the air can be expressed by the density of the water vapor contained in the air, that is, the mass of the water vapor contained in the unit volume of air Because it is difficult to directly measure the density of water vapor in the air, and the pressure of water vapor increases with the increase of water vapor density, the humidity of the air is usually expressed by the pressure of water vapor in the air, which is the absolute humidity of the air.

How to choose a thermohygrometer:

Due to the use of different temperature and humidity measurement principles, the temperature and humidity instruments are diverse, and the actual application environment and requirements of the user should be considered when selecting, such as range, output and display, installation method, sampling method, gas type, material and structure, control and monitoring requirements, environmental hazards, etc. In addition to this, it is important to pay attention to factors such as cost performance and maintenance workload:

Robust: Hygrometer sensors and housings are designed to withstand condensation, drying, extreme temperatures, dust, chemicals, or other contamination.

Cost-effective: When choosing a temperature and humidity instrument, you can't just consider the lowest level, but you should choose it based on comprehensive performance and performance. This includes **, life, maintenance, and calibration costs.

Validation: The method of calibration and whether it is easy to make is considered, even if you don't need high-precision results. Instruments that are easy to calibrate both on-site and in-situ will save you effort.

Quality reliability, average life: when the quality is not good to judge, you can start from the overall impression, inspect the quality appraisal and factory standards, investigate the history, reputation, market share and application of the manufacturer, brand-name products are better than general products, professional manufacturers' products are better than those of other manufacturers, and it is also a good way to consult other users.

Adaptability: When the use is not a single one, the adaptability of the instrument should be considered. Interchangeability: It is generally desirable that the thermohygrometer can be used interchangeably or other probes to match your main unit. Maintenance: Investigate the time requirements for regular cleaning, renewal and replacement of the hygrometer.

The indoor humidity, generally at 60 to 63%, with air conditioning, will come down, and if it is too low, people's ** dry, just like winter.

Electronic hygrometers and mechanical hygrometers are more accurate than the former.

The principle of an electronic hygrometer is to apply a moisture-sensitive material to the surface of an electronic component or to composite it into the element. When the humidity changes, the change in the physical properties of the moisture-sensitive material in the component affects the current or voltage through the electronic component, and the change value of temperature and humidity is converted through the circuit and displayed on the electronic screen, which is an electronic hygrometer.

How to operate the electronic hygrometer:

1. Push open the battery door according to the direction indicated on the back of the machine, take out the battery separator, and then replace the battery door, and the machine is ready to use.

2. Button function: (mode) to switch the clock and alarm clock display mode, set the current time, alarm clock, 12 or 24-hour clock, date (ADJ) to adjust the value of the set item; The memory shows the highest and lowest temperature and humidity values in memory, the highest and lowest temperature and humidity values in memory. (of) to switch the temperature unit in (Celsius) or of (Fahrenheit); (reset) clears all set memory values and returns to the initial state.

3. Press and hold (mode) for 1 second in the initial state, the minutes of the current time start to flash, press (adj) to adjust the number of minutes, and press (mode) continuously to set "clock", "12 24", "month (m)", and day (d) respectively.

Different types of hygrometers have different principles, taking alumina hygrometers as an example: its working principle is that the alumina film can absorb water from the surrounding gas and cause changes in its own capacitance and resistance values, and the amplitude of the change is used to represent the relative humidity of the surrounding gas. However, many people don't know how to see the humidity after buying the hygrometer, in fact, the method is very simple, the higher the value, the greater the humidity, and vice versa.

The humidity on the hygrometer is relative humidity, with higher values indicating wetter and smaller values representing drier humidity. Absolute humidity is the amount of gaseous water that air can actually hold at a fixed temperature and pressure. Relative humidity, on the other hand, is the actual absolute humidity as a percentage of the maximum amount of moisture that can be contained.

The humidity that affects the human body is usually based on the relative humidity.

Precautions for storage of thermohygrometers:

1. Warehouses that are afraid of heat, moisture, and quality are prone to change in the warehouse, one to several temperature and humidity meters should be configured in the warehouse, and at least one to several warehouses should be equipped with temperature and humidity meters in different constructions, different structures, different floors, and different commodities (categories), and the warehouses for storing some commodities can be configured with representative warehouse configurations.

2. The temperature and humidity meter in the warehouse, if only one is configured, should be placed in the middle of the warehouse, and the temperature and humidity meter should be hung on a special support.

3. The hanging height of the thermohygrometer should be spaced between the ground and the ground, and it should be basically maintained at eye level to facilitate observation.

The above content refers to Encyclopedia - Hygrometer.

Hygrometer principle: because the temperature bubble of the wet bubble thermometer is wrapped with cotton yarn, the lower end of the cotton yarn is immersed in water, and after the evaporation of water, the temperature indicator of the wet bubble thermometer is always lower than the temperature indicator (air temperature) of the dry foam thermometer, and this temperature difference is related to the speed of water evaporation (that is, the relative humidity at that time). Based on the readings of the two thermometers, the relative humidity of the air can be detected from the table or on the curve.

Humidity indicates the amount of water vapor in a gas and is divided into absolute and relative humidity. Absolute humidity is the net amount of water vapor in a gas in grams per cubic meter. Relative humidity is the ratio of the water vapor content in the gas to the water vapor content when the water vapor in the gas reaches the saturated state in the same state, and is expressed as rh (%)

Hygrometers are used in a wide range of applications, such as in ultra-pure metal smelting, textile processing, production processes such as paper and dyeing, as well as food storage and meteorological measurements, where they are often used to measure or control the humidity of air or industrial process gases.

The hygrometers used include hair hygrometers, psychrometrophic bulb hygrometers, lithium chloride hygrometers, etc., and their principles are different, but they all measure relative humidity.

Here we introduce a common hygrometer called a psychrometrophic hygrometer.

There are two thermometers with the same specifications, and the difference between the two thermometers is that the bulb of one thermometer is wrapped with soaked white gauze, which is called a wet bulb; The other bulb is in direct contact with the air and is used to determine the air temperature, which is called a dry bulb. When the relative humidity in the air is lower than 100%, the moisture will evaporate and absorb heat, making the temperature of the wet bulb lower than that of the dry bulb. The drier the air and the more intense the evaporation, the greater the temperature difference between the wet and dry bulbs, and the humidity of the environment can be measured by the temperature difference between the two.

Although the principle is very simple, the temperature difference between the wet and dry bulb represents different humidity at different air temperatures, and the relationship is very complicated. There will be a humidity comparison table on the household psychrometer, from which the relative humidity can be read, and some are equipped with a calculation plate at the bottom, and the relative humidity can also be obtained by turning the calculation disk.