A variety of thermometers have been designed and manufactured for different purposes. Thermometer, thermometer thermometer manufacturers, wholesale its design basis: the influence of temperature and thermal expansion and contraction of the phenomenon of the use of solid, liquid and gas; under constant volume conditions, gas (or steam) pressure varies with different temperature; pyroelectric effect; electrical resistance varies with temperature; heat the effects of radiation.
Generally speaking, any physical property of any substance, as long as it changes monotonically with temperature, can be used to mark the temperature and make it into a thermometer.
The working principle of various thermometers
1. gas thermometer: the use of hydrogen or helium temperature substances, because hydrogen and helium liquefaction temperature is very low, thermometer, thermometer thermometer manufacturers, wholesale close to absolute zero, so it has a wide range of temperature. This thermometer is of high accuracy, and is often used for precise measurement.
2. resistance thermometer: divided into metal resistance thermometer and semiconductor resistance thermometer, are based on the resistance value with the change of temperature characteristics of this made. Metal thermometer is mainly used for platinum, gold, copper, nickel and other pure metal and rhodium iron and phosphorus bronze alloy; semiconductor thermometer mainly uses carbon, germanium and so on. The resistance thermometer is convenient and reliable, and has been widely used. Its range of measurement is from -260 to 600.
3. thermocouple thermometer: it is a widely used thermometer in industry. Make use of thermoelectric phenomenon. Two different metal wires are welded together to form a working end, and the other ends are connected with the measuring instrument to form a circuit. When the working end is placed at the measured temperature, the electromotive force will appear when the temperature of the working end is different from the free end, so there is a current passing through the circuit. By measuring the electrical quantities, the temperature at another point can be determined by using the known temperature. It is suitable for two kinds of materials with high temperature difference, and is used for high temperature and low turbidity measurement. Some thermocouples measure high temperatures up to 3000 degrees, and some can measure temperatures close to absolute zero.
4. high temperature thermometer: a thermometer that is specially designed to measure the temperature above 500 degrees. It has optical thermometer, color thermometer and radiation thermometer. The principle and structure of the high temperature thermometer are quite complex, which is no longer discussed here. The range of measurement is from 500 to 3000 degrees, which is not suitable for measuring low temperature.
5. pointer thermometer: is shaped like a thermometer dashboard, also known as a thermometer, used to measure the temperature, with metal expansion and contraction principle. It uses bimetallic plates as a temperature sensor to control the pointer. Bimetallic plates are usually riveted together with copper sheets and iron sheets, and the copper sheets are left and the iron sheets are right. Due to the thermal expansion and contraction effect than copper iron obviously, so when the temperature rises, the copper iron pull bends to the right pointer in bimetallic drive right deflection (pointing to the high temperature); on the other hand, the temperature is low, the pointer in bimetallic drive is deflected to the left (pointing to the low temperature).
6. glass tube thermometer: glass tube thermometer is the use of thermal expansion and contraction principle to achieve temperature measurement. Because the expansion coefficient of temperature measuring medium is different from the boiling point and freezing point, the common glass tube thermometers are mainly kerosene thermometer, mercury thermometer and red pen water thermometer. It has the advantages of simple structure, convenient operation, relatively high measuring accuracy and low price. The disadvantage is that the upper and lower limits of measurement and accuracy are limited by the quality of glass and the nature of temperature measuring medium. And can not be remote, fragile. Thermometer, thermometer manufacturer, thermometer wholesale
7. pressure thermometer: pressure thermometer is the use of closed containers of liquid, gas or saturated steam heating, volume expansion or pressure changes as a signal. Its basic structure is composed of temperature, capillary and meter of three parts. The advantages of pressure thermometer are: simple structure, high mechanical strength, not afraid of vibration. The price is low, and no external energy is needed. The disadvantage is that the range of temperature measurement is limited, generally at -80~400 centigrade; the heat loss is large and the response time is slow.