1. First observe the measuring range, graduation value and 0 point, and the measured liquid temperature shall not exceed the measuring range; 2. All the glass bubbles of the thermometer shall be immersed in the measured liquid and shall not touch the bottom or wall of the container; 3. Wait for a while after the thermometer glass bubble is immersed in the measured liquid, and read after the indication of the thermometer is stable;

Digital thermometer​ uses temperature sensor to convert (temperature) into digital signal. Then the temperature in digital form is displayed through the display (such as LCD, nixie tube, LED matrix, etc.), which can quickly and accurately measure the maximum value of human body temperature. Compared with the traditional mercury thermometer, it has the advantages of convenient reading, short measurement time, high measurement accuracy, memory and prompt sound.

The rotary thermometer is made of a coiled bimetallic sheet. One end of the bimetallic sheet is fixed, and the other end is connected with the pointer. Due to the different expansion degree of the two metal sheets, the crimp degree of the bimetallic sheet is different at different temperatures, and the pointer then points to different positions on the dial. The temperature can be known from the reading on the dial.

The thermometer was first invented by Galileo in Italy from 1643 to 1592. His first thermometer was a glass tube with an open end and a glass bubble the size of a walnut at the other end. When in use, first heat the glass bubble, and then insert the glass tube into the water. With the change of temperature, the water surface in the glass tube will move up and down.

Thermometer is a tool that can accurately judge and measure temperature. It is divided into pointer thermometer and digital thermometer. According to the difference of use purpose, a variety of thermometers have been designed and manufactured. According to the difference of use purpose, a variety of thermometers have been designed and manufactured.

It can resist the corrosion of hydrochloric acid, acetic acid, oxalic acid, ammonia, phosphoric acid and 50% sulfuric acid, sodium hydroxide and potassium hydroxide at room temperature, but it is not resistant to the corrosion of strong oxidants Measure general acid, alkali and salt solutions 1. Excellent elasticity, high breaking force and good wear resistance 2. It is resistant to the corrosion of general low concentration acid-base and salt solution, but not resistant to the corrosion of oxidizing medium

The flowmeter is a two-way measurement system with three integrators installed inside: forward total amount, reverse total amount and difference total amount; It can display positive and negative flow, and has a variety of outputs: current, pulse, digital communication, Hart; The converter adopts surface mount technology (SMT), with self inspection and self diagnosis functions

Electromagnetic flow meters (EMF) is a new type of flow measurement instrument developed rapidly with the development of electronic technology from 1950s to 1960s. Electromagnetic flowmeter is an instrument that uses the principle of electromagnetic induction to measure the flow of conductive fluid according to the electromotive force induced when the conductive fluid passes through the external magnetic field.

The open communication protocol of Hart (highway addressable remote transducer) is a communication protocol between field intelligent instruments and control room equipment launched by rosement company in 1985. Hart device provides communication with relatively low bandwidth and moderate response time. After more than 10 years of development, Hart technology has been very mature abroad and has become the industrial standard of global intelligent instruments.

The working principle of the pressure transmitter​ is to replace the weak non electric pressure pressure variable collected by the sensor with a transmittable standardized signal output and amplify it at the same time to supply secondary instruments such as indicating alarm instrument, recorder and regulator for measurement, indication and process adjustment.