Knowledge About Analytical Instruments - the Choose and Buy of PH Meter of Analytical Instruments
1. The choose and buy of PH meter of Analytical instrumentsThe instrument is in food, drinking water administrative office in a factory of QS, HACCP certification necessary test equipment. We in the acidity of choose and buy time to consider the following: Pen type pH meter is mainly used to replace the function of the pH paper, has the characteristics of low accuracy, easy to use. Portable pH meter is mainly used in field and field test, to demand higher precision and perfect function. Laboratory pH meter is a kind of desktop precision analysis instruments, require high precision, complete functions, including printing, data processing and so on. Industrial pH meter is used for continuous measurement of industrial process, not only must have the measurement display function, but also has alarm and control functions, as well as installation, cleaning, anti-jamming and so on consideration of the problem. 2. According to the classification accuracy of pH meter instruments: can be divided into class 0.2, 0.1, 0.05, 0.01, the smaller the number, the higher the precision. But the chip development cost is very expensive Pointer pH meter is now rarely used, but the pointer instrument can display the data process of continuous change, so there are used in the titration analysis. 5. See the pH meter to have the supplementary function, for example with the standard RS232 interface, and a heavy is temperature compensation is automatic Or manual, automatic temperature compensation of the PH meter is more convenient than manual temperature compensation of the PH meter, between the price you will understand. Note: the pH meter | acidity meter | acidity meter these three names are the same, just the local or manufacturer is different------2. The classification of the PH meter is introduced of Analytical instrumentsThe classification of the PH meter is introduced: According to the accuracy of measurement Can be divided into class 0.2, 0.1, 0.01 or higher precision. According to the instrument volume Points have pen type (mini), portable, desktop and online continuous on-line monitoring measurement. According to the requirements of use Pen type (mini) and portable PH PH meter is commonly testing personnel to the site inspection. Select PH PH meter accuracy level is decided according to the required precision of user survey, and then according to user's ease of use and choose all kinds of shapes of PH meter. According to the points of portability, divided into: portable pH meter, desktop pH meter and pen pH meter. According to use can be divided into: laboratory pH meter, industrial online pH meter, etc. Divided into economical pH meter according to the advanced level, and intelligent pH meter, precise pH meter or divided into pH meter pointer type, digital display type pH meter. Pen type PH meter, generally made from a single range, narrow measuring range, easy for special equipment. Laboratory PH meter wide measuring range, function, high accuracy of measurement. Industry with the characteristics of the pH meter is to require good stability, reliable operation, has the certain measuring accuracy, strong environment adaptability, strong anti-interference ability, has the analog output, digital communications, upper and lower alarm and control functions, etc.------3. The working principle of dissolved oxygen instrument of Analytical instrumentsFor using activated sludge biological treatment plants, to understand the oxygen content of aeration tank is very important, increase dissolved oxygen in water, can promote the biological activity other than the anaerobic microbes, which can remove volatile substances, and easy to natural oxidation of ions, for sewage purification. The dissolved oxygen using electrochemical measurement in general. The higher the atmospheric pressure, the greater the ability of water dissolved oxygen, their relationship (Henry) by Henry's law and Dalton Dalton's law to determine, Henry's law that the solubility of a gas is directly proportional to the partial pressure. Oxygen measurement sensors by the cathode (commonly used gold and platinum) and with current counter electrode (silver), the current reference electrode (silver), electrode immersed in the electrolyte such as KCl, KOH, sensor diaphragm cover, coated electrode and the electrolyte is separated from measured liquid, only can dissolved gas permeability of coated, so to protect the sensor, can prevent the electrolyte escape, and can prevent the foreign substances of shooting and cause pollution and poison. Silver chloride precipitation on the counter electrode electrochemical equivalent insufficient (electronic), for each oxygen molecules, the cathode released four electronic counter electrode accept electronic, a current: 4 ag 4 cl - 4 agcl 4 e -. The function of the reference electrode is to determine the cathodic potential.------4. The second note of the viscometer of Analytical instrumentsThe viscometer note # 2: In the process of rotor immersed in liquid often with bubbles, in most of the rotor rotation after a period of time will rise disappear, sometimes cannot eliminate bubbles attached to the lower part of the rotor, the existence of the bubble can bring large deviation to measured data, so the leaning slowly into the rotor is an efficient way. Attention should be paid to cleaning method, can use suitable organic solvent soak, don't use metal cutting tools and other hard blow, because the surface of the rotor has serious scratches can cause the deviation of measurement results. Eight, other problems that should pay attention to. 1. Most of the instruments need to adjust the level, after the replacement of the rotor and adjust height of rotor and the level of attention at any time during the process of measuring problem, otherwise it will cause reading deviation and even unable to reading. 2. Some instruments to protect the frame, carefully read the instructions in accordance with the provisions, the installation, otherwise it will cause reading deviation. To sum up, although rotational viscometer of simple structure, easy to use, but if we don't use correctly, an instrument calibration qualified but can't get accurate measurement results, influence the quality of the product.------5. Calorimetric apparatus of Analytical instrumentsAdopt advanced single chip microcomputer system, full automatic operation, manual needed to do is to weigh, reloading and oxygen filling, instrument automatically quantitative water injection, automatic stirring, ignition, output printing results, drainage, etc Calorimetric apparatus of calorimetric system, in addition to water absorbs heat, oxygen bomb, inner barrel, thermometer and agitator is endothermic, and their heat is different, all kinds of factors is more complex, can not rely on simple mathematical calculation, only USES the calorific value of the known benchmark calorimetric system such as benzoic acid to actual calibration temperature rise per 1 to absorb heat, the heat capacity of the calorimeter is calibration. Heat capacity of the calibration is valid for 3 months, but in the following situation occurs, should immediately to calibration: 1, normal use after a significant move of the calorimeter; 2, large oxygen bomb parts replacement calorimeter: such as oxygen bomb cover, link, etc.; 3, the thermometer replacement calorimeter; 4, determination of calorific value, the inner barrel average within the cylinder at the time of actual water temperature and the heat capacity calibration temperature 5 or more; Calorimetric apparatus network advice, if the quantity of heat meter use environment for a long time without a major change, also according to the use of seasonal change every year, divided into spring, summer, autumn and winter, the calibration again.------6. The use of the water quality analyzer matters needing attention of Analytical instrumentsWater quality analyzer in use process should pay attention to the following questions: Its not closed when test is another problem because Karl fischer reagent in the experiment to absorb air moisture, would result in a delay of titration end point. Likewise, use ethyl alcohol reagents, has a similar problem, after take put as far as possible to shorten the time of reaction pool open should be paid attention to. In reaction in the pool, because when the titration reagent to locally, and the electrode is not in one place, so best to fast mixing speed to do not become turbulent, so can the fastest to the end. Titration to fast to try to shorten the test time, and in the end slow strain, which can improve the measurement accuracy. 5, after the completion of the test, be sure to drain system of Karl fischer reagent, then wash clean with methanol, never use water cleaning system, because it is not easy to volatilize, will cause the next test calibration Karl fischer reagent. Manual moisture meter, because must use glass automatic burette metering Karl fischer reagent and methanol solvent, and glass burette itself because of the pressure balance, and must be connected with the outside world. In the air relative humidity is more than 70% of the environment, should try to not arrange moisture test. The titration speed too slow will extend the test process, easy to cause the interference has been slow to reach the end.------7. Sound level meter according to sensitivity classification of Analytical instrumentsAt present, the sound level meter for measuring the noise, the meter response according to the sensitivity can be divided into four kinds: Header time constant is 1000 ms, - and used to measure the steady state noise measured value as valid. Fast gear close to the human ear response to sound. Whose hands rise time of 35 ms, used to measure the duration of the long pulse noise, such as punch, according to the hammer, the measured value for maximum RMS. The maximum value. Within the domestic type ND2 precision sound level meter installed a frequency doubling process filter pages, easy to carry to the scene and the spectrum analysis. Sound level meter in use can be divided into two categories: one kind is used to measure the steady state noise, are used to measure not steady state noise and impulse noise. Noise dosimeter is also a kind of integral type sound level meter, mainly used to measure the amount of noise exposure. Pulse sound level meter is used to measure impulse noise, the sound level meter conforms to the human ear to sound pulse response and the median time to response to sound pulse to the human ear. Now it is not only used in acoustics and electroacoustics measurement, and has been extensively used in the design of machine manufacturing, construction, transportation, environmental protection, health and defence engineering and other fields, become almost all departments must possess acoustic measuring instrument.------8. The typical structure of the ion chromatograph of Analytical instrumentsIon chromatograph of typical structure: Ion chromatograph of typical structure by infusion pump, injector valve, chromatographic column, column, detector and a data processing system. Infusion pump Both the movement of the piston rod has a time lag, just compensation mobile phase output pulse, so the velocity is quite smooth. The injection valve Amount of sampling methods is six valve sample, the method of incoming sample amount is variable scope is big, high pressure resistance, and easy to automate. The chromatographic column Ion chromatograph column packing is a hotspot of research on ion chromatograph, is the main driving force in the development of ion chromatograph, developing very quickly. Ion switch sensor is divided into two categories, namely, electrochemical detector and optical switch sensor, dc ampere, pulse electrochemical detector including conductance, amp and integral amp, etc., and optical detector including ultraviolet, or see the light and fluorescence detector. The conductance detector is the most important detectors, ion chromatography is a brief introduction is as follows. Flow conductance detector is by ion chromatography phase conduction as the basis of quantitative changes. Through to the movement of current measurement can know the concentration of the ions in the solution. And if a high electrical conductivity of the mobile phase, and the electrical conductivity of the sample is low, then the conductance detector wouldn't be effective to detect the samples of the concentration of the ions. As a result, people in the chromatographic column plus a inhibition between column and a conductivity detector, it can change the flow and the electrical conductivity of the sample, so that the sample ion sensitive detection.