What is temperature meter?
Temperature meter is a physical analysis instrument that measures the humidity of a gas.
Humidity indicates the water vapor content of gas and is expressed in two ways: absolute humidity and relative humidity. Absolute humidity refers to the absolute content of water vapor in a gas, the most commonly used unit is g/m^3. At a certain temperature and pressure, the water vapor content per unit volume has a certain limit, called the saturation water vapor content.
Relative humidity refers to the ratio of the absolute content of water vapor in a gas to the saturated water vapor content in the same volume of gas at the same temperature and pressure, commonly used as the symbol %R.H. Hygrometers are used in a wide range of applications, for example in ultra-pure metal smelting, textile processing, paper and dyeing, and other production processes, as well as food storage and meteorological measurements, often need to use hygrometers to measure or control the humidity of air or industrial process gases.
Working principle of temperature meter
Temperature meter consists of two identical thermometers. One of the thermometers is a dry-bubble thermometer, and the other is a wet-bubble thermometer.
As the wet bubble thermometer temperature-sensitive bubble is wrapped in cotton yarn, the lower end of the cotton yarn is immersed in water, the evaporation of water and the temperature of the wet bubble thermometer is always lower than the temperature of the dry bubble thermometer (air temperature) this temperature difference with the water evaporates quickly and slowly (that is, the relative humidity at the time) related. According to the readings of the two thermometers, the table or curve can find out the relative humidity of the air.
What is air humidity?
Humidity of the air can be commonly understood as the degree of humidity of the air. It has absolute humidity and relative humidity.
A. Absolute humidity
The pressure of water vapor in the air, P, is called the absolute humidity of the air.
The humidity of the air can be expressed in terms of the density of water vapor contained in the air, that is, the mass of water vapor contained in a 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 density of water vapor, the pressure of water vapor in the air is usually used to express the humidity of the air, which is the absolute humidity of the air.
B. Relative humidity
To express the degree of water vapor in the air from the saturation state, so the concept of relative humidity is introduced.
The absolute humidity of the air at a certain temperature p and the percentage of the saturation vapor pressure ps of water at the same temperature is called the relative humidity of the air at this time.
a. The saturation vapor pressure of water at different temperatures can be obtained from the table.
b. When the absolute humidity p remains unchanged and the temperature is lowered, the relative humidity of the air increases because the saturation vapor pressure of water decreases.
c. The relative humidity of the living room is 60 % to 70 % more suitable.
History of temperature meter
A temperature meter is an instrument that measures the humidity of the surrounding gas. Humidity indicates the water vapor content of gas and is divided into absolute and relative humidity. Absolute humidity is the net water vapor content in gas in grams per cubic meter. The relative humidity is the ratio of the water vapor content in the gas to the water vapor content in the gas in the same state when the gas reaches saturation, expressed as RH (%).
The Book of History records a balance device with earth and charcoal on each side of the balance. The book "Huainanzi" explains this device: When the weather is dry. When the weather is dry, the charcoal is light, the balance is tilted to the earth’s side; when the weather is wet, the charcoal becomes heavy, and the balance is tilted to the charcoal’s side. This is the earliest measurement of air humidity.
The earliest temperature meter in Europe appeared in the 15th century when an Italian invented a method of measuring humidity. This method and the Chinese use the same principle of the balance device, a ball of dry cotton at one end of the balance, and then the same weight on the other end of the weight. When the cotton absorbs the water vapor in the air it will sink and the balance will tilt towards the cotton. According to the amount of water vapor absorbed by the cotton, the water vapor content of the air can be determined.
Type of temperature meter
Temperature and humidity meter
A. Hair temperature and humidity meter
The length of hair and certain synthetic fibers varies with the relative humidity of the surrounding gas: the higher the relative humidity, the greater the length. Using this principle, a hair temperature and humidity meter can be made. When the length of the synthetic fiber changes with the relative humidity, the position of the pointer is changed by a mechanical transmission mechanism. This type of temperature meter is simple in structure and is widely used in meteorological measurements.
B. Lithium chloride temperature humidity meter
This temperature meter has a thin layer of lithium chloride coating on the surface of the detection element, which can absorb water vapor from the surrounding gas and conduct electricity. The higher the relative humidity of the surrounding gas, the greater the water absorption rate of lithium chloride, so the resistance between the two electrodes is smaller. Therefore, the magnitude of the current through the electrode can reflect the relative temperature and humidity gauge of the surrounding gas. This type of hygrometer is widely used in industrial processes.
C. Wet and dry bulb temperature meter
The usual wet and dry bulb temperature meter consists of two identical glass thermometers in close proximity to each other, one of which has a nylon mesh sleeve wrapped around the temperature pack and the other end of which is immersed in water. Due to the capillary effect, the net around the temperature packet is always kept wet state. The net cover surface moisture evaporates when the heat absorption will make the net cover temperature decrease. Thus, the temperature indicated by this thermometer (called a wet bulb thermometer) is lower than the temperature indicated by another thermometer (called a dry bulb thermometer) without the net sleeve. The lower the relative humidity of the surrounding gas, the faster the evaporation of water from the mesh jacket, and thus the greater the temperature reduction. According to this temperature difference and dry bulb temperature, the relative humidity of the surrounding gas can be found in the control table attached to the instrument. This temperature and humidity meter has a simple structure and is mainly used for meteorological measurements and indoor air humidity measurements.
D. Aluminum oxide temperature meter
It works on the principle that an alumina film absorbs water from the surrounding gas and causes a change in its own capacitance and resistance, and the magnitude of the change is used to indicate the relative humidity of the surrounding gas. This type of temperature meter is mainly used for humidity measurement of industrial process gases and can measure a wide range of relative humidity.
Laboratory temperature and humidity control with temperature meter
In laboratory monitoring projects, different laboratories have requirements for temperature and humidity, and most experiments are carried out in a well-defined temperature and humidity environment. Laboratory environmental conditions directly affect the results of various experiments or tests, and the conduct of each experiment requires precise and reliable monitoring instruments to provide accurate data on environmental parameters. In addition, factors such as laboratory temperature and humidity may not only cause instability in equipment performance, but even directly affect the service life of instruments and equipment. Therefore, laboratory temperature is also an important part of laboratory management. Laboratories need the right temperature and humidity. Indoor microclimate, including temperature, airflow speed, humidity, have an impact on the personnel and equipment working in the laboratory.
The suitable temperature is 18~28℃ in summer, 16~20℃ in winter, and the suitable humidity is between 30%~80%.
Except for special laboratories, temperature and humidity have little effect on most physical and chemical experiments. However, balance rooms and precision instrument rooms should be controlled according to the needs of temperature and humidity.
Environmental conditions temperature and humidity control aspects of the elements considered to ensure that the environmental temperature and humidity of the experimental operation are able to meet the needs of the various processes of the experimental procedures. We mainly from the following aspects to develop the laboratory environment temperature and humidity control range.
A. Identify the requirements of each task for environmental temperature and humidity
This requirement is mainly used to identify the needs of instruments, reagents, experimental procedures, and humane considerations of laboratory staff (human body in the temperature of 18-25 ℃, relative humidity in the range of 35-80% of the overall feeling of comfort, and from a medical point of view, there is a certain causal relationship between environmental dryness and inflammation of the throat) four elements of comprehensive consideration, listed on the temperature and humidity control range requirements list.
B. Select and develop an effective environmental temperature and humidity control range
In addition to extracting the narrowest range from all the requirements of the above elements as the permissible range of environmental control in this laboratory so as to develop management procedures for the control of environmental conditions, and the need to develop reasonable and effective SOPs based on the actual situation of the department.
C. Maintain and monitor
Through various measures to ensure that the temperature and humidity of the environment in the control range, and environmental temperature and humidity monitoring and monitoring records, more than the allowable range of timely measures, open the air conditioning to adjust the temperature, and open the dehumidifier to control humidity. At this time, a temperature meter can be considered for use.
How to buy temperature meter?
ANTITECK provide lab equipment, lab consumable, manufacturing equipment in life sciences sector. If you are interested in our temperature meter or have any questions, please write an e-mail to info@antiteck.com, we will reply to you as soon as possible.
