Bimetallic thermometer info from factory

full introduction


Bimetallic thermometer, is the general term of temperature measuring instrument, can accurately judge and measure the temperature. The design is based on the phenomenon that the solid, liquid and gas expand and contract under the influence of temperature. With kerosene, bimetallic thermometer, alcohol bimetal bimetal thermometer, mercury thermometer, gas bimetal bimetal thermometer, resistance thermometers, thermocouple, bimetallic thermometer 1, bimetallic thermometer and light radiation measuring bimetallic thermometers, bimetal bimetal thermometer and various bimetallic thermometer for us to choose, but must pay attention to the correct method of use, understand the characteristic of the thermometer, facilitate better use.


A variety of bimetal thermometers have been designed and manufactured for different purposes. The design is based on the following factors: the expansion and contraction of solids, liquids and gases under the influence of temperature; Under constant volume conditions, the pressure of a gas (or steam) varies with temperature; The effect of thermoelectric effects; Resistance varies with temperature; Effects of thermal radiation, etc.

In general, any physical property of any substance which varies monotonously and markedly with temperature may be used to mark the temperature of a bimetallic thermometer.

All kinds of bimetal thermometers work

1. Gas bimetal thermometers: Hydrogen or helium are used as temperature measuring materials, because the liquefaction temperature of hydrogen and helium is very low, close to absolute zero, so it has a wide range of temperature measuring. This bimetal thermometer is highly accurate and is often used for precision measurements.

2 resistance bimetal thermometer: divided into metal resistance bimetal thermometer and semiconductor resistance bimetal thermometer, are based on the resistance value with the temperature change of this property made. Metal bimetal thermometer is mainly used platinum, gold, copper, nickel and other pure metal and rhodium-iron, phosphor bronze alloy; Semiconductor bimetal thermometers mainly use carbon, germanium and so on. Resistance bimetal thermometers are easy to use and have been widely used. It can be measured from -260℃ to about 600℃.

High precision bimetal thermometers
High precision bimetal thermometers
Thermoelectric couple bimetal thermometer: it is a widely used temperature measuring instrument in industry. Made of thermoelectricity. Two different metal wires are welded together to form a working end, and the other two ends are connected with the measuring instrument to form a circuit. When the working end is placed at the measured temperature, the temperature of the working end is different from that of the free end, an electromotive force will appear, and a current will flow through the loop. By means of electrical measurements, we can determine the temperature at one place by taking advantage of the temperature at one place. It is suitable for the temperature difference between two substances, mostly used for high temperature and low turbidity measurement. Some thermocouples measure temperatures as high as 3000 ° C, while others measure temperatures close to absolute zero.

4. High temperature bimetal thermometers: bimetal thermometers are specially used to measure the temperature above 500℃. There are optical bimetal thermometers, colorimetric bimetal thermometers and radiation bimetal thermometers. The principle and construction of high temperature bimetal thermometers are complex and will not be discussed here. Its measurement range is 500℃ to above 3000℃, not suitable for low temperature measurement.

5 pointer type bimetal thermometer: is shaped like the instrument panel of bimetal thermometer, also known as the thermometer, used to measure room temperature, is made of metal expansion and contraction principle. It is a bimetallic element as a temperature sensor for the control of the pointer. The bimetallic sheet is usually riveted together with copper sheet and iron sheet, with the copper sheet on the left and the iron sheet on the right. Since copper's thermal expansion and cold contraction effect is much more obvious than iron's, when the temperature rises, the copper sheet pulls the iron sheet to bend to the right, and the pointer will turn to the right under the drive of the bimetal sheet (pointing to high temperature). On the contrary, when the temperature becomes low, the pointer is driven to the left by the bimetal plate (pointing to the low temperature).

6. Glass tube bimetal thermometer: glass tube bimetal thermometer is the use of heat expansion and cold contraction principle to achieve the temperature measurement. Because the expansion coefficient of temperature measuring medium and boiling point and freezing point are different, so our common glass tube bimetal thermometer mainly have: kerosene bimetal thermometer, mercury bimetal thermometer, red pen water bimetal thermometer. Its advantages are simple structure, easy to use, relatively high measurement accuracy and low price. The disadvantage is that the upper and lower limits and precision of measurement are limited by the quality of glass and the nature of temperature measuring medium. And can not be far away, fragile.

7. Pressure bimetal thermometers: Pressure bimetal thermometers use the volume expansion or pressure change of liquid, gas or saturated vapor heated in a closed container as a measurement signal. Its basic structure is composed of three parts: temperature packet, capillary tube and indicator table. The advantages of pressure type bimetal thermometer are: simple structure, high mechanical strength, not afraid of vibration. It is cheap and requires no external energy. Disadvantages are: temperature range is limited, generally in -80~400℃; The response time of high heat loss is slow.

8 mercury bimetal thermometer: mercury bimetal thermometer is an expanded bimetal thermometer, the freezing point of mercury is -38.87℃, boiling point is 356.7℃, used to measure 0--150℃ or 500℃ within the range of temperature, it can only be used as a local monitoring instrument. Using it to measure temperature is not only simple and intuitive, but also can avoid the error of external remote bimetal thermometer.


Inventions and Improvements
Bimetallic thermometer
Bimetallic thermometer
The first bimetal thermometer was invented in 1593 by the Italian scientist Galileo (1564~1642). His first bimetal thermometer was a glass tube with an open end and a glass bubble the size of a walnut at the other end. To use, heat the glass bubble and then insert the glass tube into the water. As the temperature changes, the water in the glass tube moves up and down, and by how much it moves, the temperature changes and how high it is. Bimetallic thermometer has the effect of heat expansion and cold contraction so this bimetallic thermometer, by the external atmospheric pressure and other environmental factors, so the measurement error is large.

Later Galileo's students and other scientists, on the basis of repeated improvements, such as the glass tube upside down, put liquid in the tube, the glass tube closed. What stands out is the bimetallic thermometer made by The Frenchman Brio in 1659. He reduced the volume of the glass bubble and changed the temperature measuring substance into mercury, which formed the prototype of the bimetallic thermometer. The Dutchman Whalenheit invented more accurate bimetal thermometers, using alcohol in 1709 and mercury in 1714. He observed the boiling temperature of water, the temperature at which water mixed with ice, and the temperature at which salt water mixed with ice; After repeated experiments and approval, the freezing temperature of a certain concentration of salt water was set at 0℉, the freezing temperature of pure water was set at 32℉, and the boiling temperature of water at the standard atmospheric pressure was set at 212℉. This is the bimetallic thermometer.

At the same time as Fahrenheit's bimetal thermometer, Lemuel (1683~1757) also designed and manufactured a bimetal thermometer.
Bimetallic thermometer
Bimetallic thermometer
He thought that the coefficient of expansion of mercury was too small to be used as a temperature measuring substance. He concentrated on the merits of using alcohol as a temperature measuring substance. He repeatedly found that the volume of alcohol, containing one-fifth of water, expanded from 1,000 to 1,080 units between the freezing and boiling temperatures of the water. Therefore, he divided the freezing point and boiling point into 80 parts, as the temperature of his bimetal thermometer, this is the Rehmander bimetal thermometer.

More than 30 years after the Fahrenheit bimetal thermometer was made, the Swede Perseus improved the scale of the Fahrenheit bimetal thermometer in 1742. He set the boiling point of water at 0 degrees and the freezing point of water at 100 degrees. Later, his colleague Schlemmer reversed the values of the two temperature points (boiling at 100 degrees and freezing at 0 degrees) to get the percentile temperature, or Celsius, expressed in degrees Celsius. The relationship between Fahrenheit and Celsius temperature is ℉=9/5℃+32, or 5/9(℉-32).

Britain and the United States use Fahrenheit, Germany uses Reich's temperature, and the world science and technology and industrial and agricultural production, as well as China, France and other countries use Celsius temperature.

Type of instrument in this section
With the development of science and technology and the need of modern industrial technology, temperature measurement technology has been constantly improved and improved. As the range of temperature measurement is more and more wide, according to different requirements, different needs of temperature measurement instruments are manufactured. Here are a few.

Rotating bimetal thermometer
The rotary bimetal thermometer is made of a coiled bimetal sheet. One end of the bimetal plate is fixed and the other end is connected to the pointer. Due to the different degree of expansion of two metal pieces, the curl degree of bimetal pieces is different at different temperatures. Then the pointer refers to the different positions on the dial. From the reading on the dial, the temperature can be known.

Semiconductor bimetal thermometers
The resistance of semiconductor is different from that of metal. When the temperature rises, the resistance of semiconductor decreases and the range of change is larger. Therefore, a small amount of temperature change can also make a significant change in the resistance, made of bimetal thermometers have higher precision, often referred to as the temperature sensor.

Thermocouple bimetal thermometers
A thermocouple bimetal thermometer consists of two different metals connected to a sensitive voltmeter. Metal contacts at different temperatures produce different potential differences at both ends of the metal. The potential difference is so small that a sensitive voltmeter is needed to measure it. From the reading of the voltmeter, you can know what the temperature is.

Optical pyrometer
If the temperature of an object is high enough to emit a large amount of visible light, the amount of its thermal radiation can be measured to determine its temperature. This bimetal thermometer is called an optical bimetal thermometer. The bimetal thermometer consists of a telescope with a red filter and a set of circuits with small bulbs, ammeters and variable resistors. Before use, establish a relationship between the temperature of the filament at different brightness and the reading on the galvanometer. When in use, adjust the resistance of the telescope to the object to be measured, so that the brightness of the bulb is the same as the object to be measured, then the temperature of the object to be measured can be read from the galvanometer.

Liquid crystal bimetal thermometer
Liquid crystals made with different formulations have different phase transitions at different temperatures, and when they undergo phase transitions, their optical properties change, causing the liquid crystals to look discolored. If liquid crystals of different phase transition temperatures are coated on a piece of paper, the temperature can be known by the change in color of the liquid crystals. The advantage of this bimetal thermometer is that it is easy to read, but the disadvantage is that it is not accurate enough. It is often used in ornamental fish tanks to indicate water temperature.

Digital bimetal thermometer
Introduction to the

A digital thermometer uses a temperature sensor to convert (temperature) into a digital signal,
Bimetallic thermometer
Bimetallic thermometer
Then displays (such as LCD, digital tube, LED matrix display of temperature in digital form, can rapidly and accurately measure the body temperature to the highest level, compared with the traditional mercury thermometer, is easy to read Numbers, with short time and high measuring accuracy, can memory and has the advantages of prompt, especially digital thermometer with no mercury, harmless to the human body and the surrounding environment is especially suitable for hospitals, family use.

Method of use

1. Before using the thermometer, the head of the thermometer should be disinfected with alcohol.

2. Press the switch and the buzzer immediately emits A beeping sound, as shown in Figure A of the display, for about 2 seconds.

3. The monitor then shows the temperature of the last lateral flow as shown in Figure B (assuming the last measurement was 36.5 ℃), and the well lasts about 2 seconds. The monitor may then display as shown in Figure C. The '℃ 'symbol flashes to indicate that the thermometer is in a waiting state. (If the room temperature is higher than 32 ℃, the thermometer will display room temperature instead of as shown in Figure D, and the '℃ 'symbol will constantly flicker).

4. Use a thermometer to take your temperature. When taking your temperature, the temperature displayed rises gradually, while the '℃ 'symbol flashes constantly.

5. When the temperature rising speed is less than 0.1 ℃ within 16 seconds, the '℃' symbol stops flashing, and the thermometer gives a beeping prompt sound for about 5 seconds. At this time, the thermometer finishes measuring and the temperature value displayed can be read.

Mercury bimetal thermometer
The mercury must be collected immediately with a dropper and brush
Digital thermometer display information description
Digital thermometer display information description
, and cover with water (preferably glycerin), and then sprinkle the contaminated area with sulfur powder, no liquid after (generally about a week) before cleaning.

This bimetal thermometer does not have an estimated reading. Or the last digit of the read number is the exact value, so you don't need to evaluate the number after the read score value.

Use of mercury bimetal thermometers

The use of bimetallic temperature timing, first to see its range (measuring range), and then see its minimum indexing value, that is, each small cell represented by the value. Choose an appropriate bimetal thermometer to measure the temperature of the object being measured. The vacuole of the bimetal thermometer should be in full contact with the measured object, and the glass bubble should not touch the side wall or bottom of the measured object; When reading, the bimetal thermometer should not leave the object under test, and the eye line should be with the bimetal thermometer in the liquid level.

1. Check before use (check can be carried out by using standard liquid temperature multi-branch comparison method or bimetal thermometer with higher accuracy).

2. The use of a measurement whose temperature exceeds the maximum scale of the bimetal thermometer is not permitted.

3. Bimetal thermometers have thermal inertia and should be read after the bimetal thermometer reaches a stable state. Read at the highest tangent of the temperature convex meniscus and look straight at it.

4. Do not use as a stirring rod.

5. Mercury bimetal thermometers shall be vertical or oblique to the flow direction of the working medium under test.

6. Mercury bimetal thermometers often break mercury columns. The elimination methods are as follows:

(1) Cold repair method: the temperature of the bimetal thermometer inserted into dry ice and alcohol mixture (temperature shall not exceed -38℃) for cold shrinkage, so that the mercury in the capillary all contracted to the temperature of the package.

(2) thermal repair: the bimetal thermometer slowly inserted temperature slightly higher than the upper limit of the thermostatic trough, so that the mercury broken part and the whole mercury column connected, and then slowly take out the bimetal thermometer, gradually cold to room temperature in the air.

Division value of this section
Instrument name Precision grading value, ℃(Celsius)

Bimetal bimetal thermometers 1,1.5, 2.5, 0.5~20

Pressure bimetal thermometers 1,1.5, 2.5, 0.5~20

Glass liquid bimetal thermometer 0.5~2.5 0.1~10

Thermal resistance 0.5~3 1~10

Thermocouple 0.5~1, 5~20

Optical pyrometer 1~1.5 5~20

Radiation bimetal thermometer (thermopower)1.5 5~20

Partial radiation bimetal thermometers 1~1.5 1~20

Colorimetric bimetal thermometers 1~1.5





How to use this paragraph
Use of bimetallic thermometers in laboratories

When using a bimetal thermometer to measure the temperature of a liquid, the correct method is as follows:

1. Firstly observe the measuring range, dividing value and 0 point, and the measured liquid temperature should not exceed the measuring range;

2. The glass bubble of the bimetal thermometer should be immersed in the measured liquid without touching the bottom or wall of the container;

3. After the glass bubble of the bimetal thermometer is immersed in the measured liquid, wait for a while, and then read after the indicator of the bimetal thermometer stabilizes;

4. The glass bubble of the bimetal thermometer should remain in the liquid while reading, and the line of sight should be level with the upper surface of the liquid column of the bimetal thermometer.

Caution: Do not shake before the temperature is measured.

Comparison of three bimetal thermometers, namely, thermometer, thermometer (mercury, alcohol, kerosene) for experimental use:

Experimental bimetal thermometers

A thermometer

thermometer

The principle of

Liquid expands when hot and contracts when cold

structure

Without reducing

There are reducing

Without reducing

Precautions for Use

Cannot leave the measured object to read

Readings can be taken away from the measured object

Cannot leave the measured object to read

Temperature measurement

Can't jilt

Before you left

Can't jilt

range

- 20 ℃ to 110 ℃

35 ℃ to 42 ℃

- 30 ℃ to 50 ℃

Dividing the value

1 ℃

0.1 ℃

1 ℃

Temperature measurement techniques

When measuring the surface temperature of luminous objects, such as aluminum and stainless steel, the surface reflection is affected
The guinness World Record for the largest bimetal thermometer
The guinness World Record for the largest bimetal thermometer
Sound infrared thermometer reading. Before reading the temperature, a rubber strip can be placed on the metal surface. After the temperature is balanced, the temperature of the strip area can be measured.

In order for an infrared thermometer to be able to move from the kitchen to the refrigerated area and still provide accurate temperature measurements, it is necessary to take measurements in a new environment over a period of time to reach a temperature equilibrium. It is better to keep the thermometer in a place where it is often used.

An infrared thermometer reads the internal temperature of a liquid food, such as soup or sauce, which must be stirred, and then measures the surface temperature. Keep the thermometer away from the steam to avoid contaminating the lens, resulting in incorrect readings.