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Meizhou Dapu instrument metrology verification welcome to visit and learn

Meizhou Dapu instrument metrology verification welcome to visit and learn

article source: WorldCom calibration test release time: 10:25:45

product brand WorldCom calibration test product model st2028 production city China Shipping city national total supply 10000 minimum starting order 1 product unit price 1 unit of measurement product details

Meizhou Dapu instrument metrology verification welcome to visit and learn

aggregation The polymer is bonded by many small molecules (monomers). The number of monomers in each long molecule in the polymer is not exactly the same, so the molecular weight is not uniform. Polymer molecular weight is a statistical molecular weight. According to different statistical methods, the definition of molecular weight is also different. Commonly used definitions are as follows:

(1) number average molecular weight: the sum of the product of the mole fraction of various molecular weight components and their corresponding molecular weight in the polymer system

(2) weight average molecular weight: the sum of the product of the mass fraction of various molecular weight components and their corresponding molecular weight in the polymer system

(3) viscosity average molecular weight: the molecular weight calculated from the relationship between intrinsic viscosity h and molecular weight

(4) Z average molecular weight: in a polymer sample, the Z value fraction of each molecular weight component and its phase are the sum of the product of the molecular weight of steel with higher requirements

welcome to Meizhou Dapu instrument metrology verification. The surge signal generator has large current, high voltage and wide frequency band. It can not be calibrated directly with general instruments. This paper presents a simple and easy comparative test method to calibrate the short-circuit current of the surge signal generator. The surge signal generator shall simulate the surge voltage generated by lightning transient and switching transient as much as possible. According to the mechanism of interference generation, when the interference source and the port of the tested equipment are in the same line, such as in the power network (direct coupling), the signal generator simulates a low impedance source; When the interference source and the port of the equipment under test are not in the same line (indirect coupling), the signal generator simulates a high impedance source. At present, the manufacturers of surge signal generator mainly include Swiss emtest company, American thermokeytek company and Japanese NOISEKEN company. All equipment characteristics meet iec61000? 4? 5 (gb/t17626.5), the main characteristics and performance of the combined wave signal generator are as follows [3]: open circuit output voltage: 0.5 ~ 4.0kv

there are many different methods for measuring the molecular weight of polymers, which are applicable to different ranges and have their own corresponding measuring instruments. The more common of these instruments are the following

(1) boiling point altimeter. Instrument calibration boiling point altimeter measures the number average molecular weight. It consists of boiling chamber, thermostatic jacket, temperature measuring device and other main parts. Pure solvent and sample solution are respectively installed in the two boiling chambers. There are steam lift pumps, heaters, temperature measuring elements, etc. in the chambers, which are surrounded by circulating water jackets. When measuring the sample, heat the boiling chamber to make the solution and solvent boil, use the steam lift pump to lift the boiling liquid to the temperature measuring element, measure the rise of the boiling point of the solution relative to the boiling point of the solvent, and calculate the molecular weight of the solute based on this

(2) vapor pressure permeameter. The vapor pressure permeameter also measures the number average molecular weight. It consists of a gasification chamber, a thermostatic furnace and a temperature measuring instrument. The gasification chamber is a sealed structure, in which there are two thermistor probes supporting liquid drops, and there is a stainless steel above each probe, which can retain the liquid. The upper parts of the two drip holes are respectively aligned with a drip tube containing liquid. Suzhou instrument calibration gasification room is a thermostatic furnace with controllable furnace temperature. The two thermistors for measuring the droplet temperature form two arms of the temperature measuring bridge. Before measuring the sample, first drop a small amount of solvent into the two drop holes, read out the electric bridge equilibrium value, then drop a certain amount of solvent into one drop hole, and drop a certain amount of solution to be measured into the other drop hole, then read out the electric bridge value, measure the temperature difference between the solution and the solvent, and calculate the number average molecular weight accordingly

welcome to Meizhou Dapu instrument metrological verification. The metrological testing laboratory is a professional metrological testing laboratory registered by the state market supervision administration and qualified by the standards of the Bureau of quality and technical supervision in accordance with the Metrology Law of the people's Republic of China and relevant metrological regulations and management regulations. It has a completely independent, legal and fair status as a third party. The laboratory has been recognized by the China National Accreditation Society for conformity assessment and cnasl3170, Therefore, it has been recognized by the national and regional laboratory accreditation bodies that have signed the multilateral agreement on mutual recognition with CNAs. The reports issued within the scope of accreditation have been recognized and recognized by other members of the multilateral mutual recognition agreement (ILAC MRA) of the International Laboratory Accreditation Cooperation Organization. The data issued can be traced back to the national benchmark and the international system of units. It is necessary to closely inspect whether there is leakage caused by loosening of each joint and take corresponding measures to deal with it; (SI), the report issued fully meets the traceability requirements of iso/iec17025 and ISO9000 family. The laboratory has a high-quality measurement and testing team mainly composed of senior engineers who have worked in the measurement and testing department for many years

(3) membrane osmometer. Membrane osmometer, referred to as osmometer for short, is an instrument for precise determination of number average molecular weight. It is mainly composed of a permeation measuring cell and an optical measuring system. The permeation measuring tank is a stainless steel tank with a small volume. A semi permeable membrane is placed at the horizontal position in the middle of the tank, which divides the tank into the upper solution chamber and the lower solvent chamber. An air bubble and a sensitive photoelectric detector are installed in the capillary connected to the solvent chamber. When Suzhou instrument calibrates and measures the sample, fill the solution and solvent into the solution chamber and the solvent chamber respectively, use the photoelectric detector to detect the displacement signal of the bubble, and keep the bubble at its original position through the electronic servo mechanism. The measured static pressure is the osmotic pressure, and then calculate the molecular weight of the polymer based on this

(4) light scattering instrument. Light scattering instrument, also known as light scattering photometer, measures the weight average molecular weight of polymer. The light scattering instrument mainly includes light source, incident light collimation system, scattering cell, scattered light intensity measurement system and so on. The light source is a medium voltage or high voltage arc lamp, and the scattering cell is a glass cell with square, rectangular and circular shapes. The scattered light intensity is converted into an electrical signal by a photomultiplier tube for measurement. Before Suzhou instrument calibrates the measurement sample, calibrate the instrument with reference materials, and then put the filtered and dedusted solvent and solution into the scattering cell to measure the scattered light intensity of the solvent and several different concentrations of solutions at different angles, and then calculate the weight average molecular weight

(5) capillary viscometer. Capillary viscometer is a supplier that simply competes for price, has no technical background and parallel interaction ability, and will be eliminated to measure the intrinsic viscosity of polymer η Suzhou instrument calibration commonly used is the Ubbelohde capillary viscometer. Solution viscosity is related to temperature, solution concentration and polymer molecular weight. When the temperature and polymer system are determined, the solution viscosity is only related to the concentration and polymer molecular weight, so the polymer molecular weight can be calculated

(6) gel permeation chromatograph. Gel permeation chromatograph is a widely used instrument for measuring the molecular weight and distribution of polymers in modern times. When measuring the sample, first draw the calibration curve with the narrow distribution polymer molecular weight reference material, then inject the prepared sample solution into the chromatographic column for separation, detect the chromatographic signal by the detector, calibrate the Suzhou instrument, read the corresponding molecular weight from the calibration curve according to the elution volume or time, and calculate the molecular weight distribution from the peak height

welcome to Meizhou Dapu instrument metrological verification to visit and learn the unqualified, qualified and unqualified data, which will be displayed on the screen at the same time; Finally, for all calibration finished items, the program automatically saves all information and data of the testing instrument, and generates reports in compliance with relevant documents. In the whole process of automatic calibration, it is only necessary to build the communication bus and connect the measuring lines between instruments, input the equipment information in the system, and select the calibration items. Other work is completed by the computer. First, manually set the address of each instrument on the communication bus, which can ensure the normal "dialogue" between the computer and the instruments and equipment; Second, the program automatically sets the technical parameters for the required instrument output or data collection, and automatically sends them to the instrument equipment through the software, so that it can change its measurement function, measuring range, resolution, filter, sampling time, output value, etc. according to the set value specified by the software; Thirdly, the program processes and analyzes the collected data in the background, judges the data according to the technical indicators, and gives the final conclusion: qualified and unqualified

(7) ultracentrifuge. When the rotating speed of the centrifuge exceeds 106 r/min, a centrifugal force 106 times the gravity can be generated, and the particles in the solution can settle and diffuse at the same time. The molecular weight of polymer can be calculated by using the sedimentation constant, diffusion coefficient and the relationship between solute and molecular weight in polymer solution

polymer molecular weight reference materials are divided into primary and secondary levels. The primary standard material is polystyrene with narrow distribution, which is determined by absolute method and high accuracy method, and is used for the transmission of molecular weight value and the calibration and evaluation of high-precision instruments and analytical methods; The secondary standard material is also a narrow distribution polymer, and its successful experience is worth learning. It has many varieties and wide measurement limit. It is mainly used for the calibration of analytical and measuring instruments, and also as a working standard

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