How to Use an Analytical Balance
If it is not centered, center it by turning the leveling screws on the bottom toward the back of the balance. Once the balance is leveled, close all the chamber doors and press the control bar on the front of the balance. After a few seconds, a row of zeros will appear. This indicates that the balance is zeroed and ready for use. Level and Zero the analytical balance. Level the balance; look at the leveling bubble on the base of the unit. If it not centered, center it by turning the leveling screws on the bottom toward the back of the balance. Zero the balance; after the leveling is .
This booklet is provided for the basic purpose of advising the laboratory worker, student and scientist on the care and use of the Precision Balance. It is based upon the experience of over years of manufacturing Balances, fortified by many sugges-tions from customers and scientific organizations.
Our thanks go out to them for their assistance in round-ing out the practical usefulness of this work. We are presenting what can cause hair loss only the basic fundamen-tals. No attempt is made to discuss specialized techniques of weighing, or the operation of special -purpose balances. It is obviously impossible to create a comprehensive text book within this small compass. We therefore treat only those situations which arise in general laboratory practice.
Copyright Firmness of Support. Freedom from Vibration. Protection from Air Currents. Protection from Dust Fumes. Simple direct weighing. Simple Substitution weighing. Deflection Methods: 1. Simple deflection method. Other deflection methods. Temperature Equality. Equality of Relative Humidity. Checking the Sensitivity. Check- ing the Sensitivity Reciprocal. Checking the weighing chain. Checking the rider concentricity. Checking the beam notches. Checking the damper.
It became a science in its own right as man progressed from the age of alchemy to the systematic study of chemistry. Lavoisier made the transition when he isolated hydrogen, oxygen, and nitrogen.
The traditional concept of 'fire, air, earth and water' was swept away, and a new understanding of the universe, with elements as building blocks, took its place. These new elements were predictable, stable. As soon as it was understood that weight was related to the nature of individual elements, infinitely precise weighing devices became a necessity. The laboratory balance was born. Later, it evolved into a dependable instrument when the problem of protecting the knife-edge pivot bearings was how to zero an analytical balance by a stirrup-like arrangement which lifted the knife edge off the bearing surface when not in use.
Then, early in the nineteenth century, Justin von Liebig created the still more precise long-beam balance. Weights themselves, according to most opinion, were standardized some time around the French Revolution, and aalytical art of infinitely close-tolerance weighing became the heart of man's search for scientific truth. In the development of the modern Analytical Balance the name Becker has always been outstanding.
Christopher Becker and his two sons, Ernst and Christian, started the manufacture of analytical balances and weights in the United States in At the end of the Civil War, manufacturing was resumed until, inanalyticaal two sons established the business under the name, Becker Bros.
Christian Anaytical, as it is known today, was established in when Ernst died, and his brother adopted the present name. Based on the contributions of the Becker family, the precision balance of today is the finest instrument balsnce its kind ever developed.
It measures far more delicate differences in mass. The weights are of a still higher order of precision. The balance mechanism is better protected, easier to use, and easier to guard from abuse.
The infinitesimal fractions of weight which it will measure how to attract women at the club still the most scientifically important measurements of mass.
Every man entrusted with the manipulation of a balance does well to know his balance, to respect its capacity for scientific exactness, and to handle it accordingly. For precision weighing the rider balance is one of the what constitutes child abandonment in california refinements employed.
The principal elements. Thus, delicate weighing procedures are not endangered by external factors. The notched beam analyrical the adding of additional weight up to one gram, in mg. All weight adjustments from 0. This can be done while the beam is swinging. It results in an important saving of time.
The magnetic damper brings the indicator to rest quickly by stopping analytixal swinging or oscillation of the beam. It means still greater rapidity in weighing while preserving the delicate knife edges. The projection of a reading through a magnifying optical system makes it possible to perform fast, repetitive weighings.
The ideal system provides a direct reading right from the screen equipped with a bxlance or similar device for fractions of divisions on the scale Balances equipped with this device must be highly accurate, as any small error is magnified through the projection system.
For the protection of its all-important knife edges and delicate parts, a Precision Balance is disassembled for shipment, and its parts are packed separately. While only the experienced laboratory worker should undertake the delicate task of assembling a balance, it may be well for all to understand something of how it is done, and how the delicate parts are handled.
It is not our purpose in this booklet to give complete and specific instructions on unpacking and assembling an analytical balance. Natu-rally, this procedure will how to make good hash browns from scratch with the type and make of balance. Therefore, we suggest tk you follow the manufacturer's assembly instructions, which are ordinarily supplied with a new balance.
When a balance is unpacked, retain the special box for the beam and other loose parts in case the balance need be disassembled for transporting or shipping at a later date. When entrusted with the unpacking and assembly of how to identify types of trees by bark new balance, there are a few general precautions, however, which the individual should observe in every case:.
Before you start to assemble the balance, make sure you know where parts go and how to put them in place. Be extremely careful of the knife edges. Rememberan analytical balance how to teach a circuit training class a precision instrument, be gentle and cautious in all assembly analyticwl.
It is fundamental that any balance for precision weighing be 1 solidly, rigidly supported, 2 free from vibration, 3 shielded from air currents, excessive humidity and varying temperatures, and 4 protected from corrosive fumes or vapors. The sensitivity of the balance and the accuracy of its readings demand a thoughtful selection of location and preparation of the support.
Consider the following factors. The supporting surface must be extremely rigid. When the beam is released and equilibrium is obtained, any pressure on the support must not cause any visible movement of the pointer.
The balance should be placed upon a solidly constructed bench or analytiical. The type of construction of the building in-volved dictates whether the table or bench should be isolated from the wall or rigidly attached to the wall. If isolated from the wall, the bench or table must rest firmly on the floor and must be anchored securely. The level of the support should be permanent.
This elimi-nates repeated relevelling of the balance case and the readjust-ment of the zero point. The major thing to guard against is a lack of rigidity in the support which might permit tilting during the weighing operation. The balance support should be free from balanve vibration that produces a visible effect upon the operation of the balance itself.
Some modern balances have built-in vibration dampers. Otherwise, satisfactory elimination of vibration at hos balance may sometimes be zwro by mounting on a heavy lead slab, supported on a sponge rubber cushion of medium resistance. Balances should be mounted in a draft free area so that when the balance door is opened, air currents will not be set up inside the case. Any perceptible draft in the vicinity of the balance case interferes with weighings. A balance should not be located near hot or cold objects, such as cold windows, radiators, electric ovens, stills, or areas that are at a different temperature than the rest of the room.
When subjected to uneven temperature conditions, convection currents may be balsnce up within the balance case. Such currents, no matter how minute, can spoil the regularity with which successive swings of the beam decrease in amplitude. This is called irregular falling off. It may even cause the zero readings of subsequent readings to vary. Sunlight, or illumination from high-powered lamps in close proximity, should not be allowed to shine on the balance. Symmetrical illumination of the balance is preferred so that one arm of the beam or one side of the case, is not heated more than the other.
Even symmetrical radiation may sometimes produce uneven heating effect. Therefore, it is essential to limit the total amount of illumination, or other radiation.
These cau-tions may leave much unsaid, but there is no absolute rule to assure perfect temperature and radiation conditions. For normally adequate illumination, common sense must govern. Thirty to fifty watt lamps may be used a few feet from the case. This will not harm most analytical work. In general, temperature must be constant during weighing, as well as for a considerable period beforehand. The constancy required varies for the weighing of objects of different size and character, and for different types and styles of balances.
A change of a few degrees in 4 or 5 hours is not likely to cause trouble in ordinary analytical work. It should wn noted, however, that falling temperature is much more likely to cause trouble than is a rising temperature. IMPORTANT In order to avoid the danger of changes in atmos-pheric conditions, many laboratories have found it advantageous to install Weighing Rooms, with air conditioning for maintenance of constant tempera-ture and humidity.
Preparing the balance for use
Dec 27, · Protect hygroscopic samples from moisture until just prior to weighing. Place analytical balances in a protected environment away from temperature extremes such as direct sunlight, heating and AC vents. Avoid heavy traffic that causes vibrations in the weighing area. Avoid overloading, which could cause hysteresis of mechanical parts. How Precise Is an Analytical Balance? Precision balances, which are also called top-loading balances or ordinary balances, offer between zero and three digits to the right of the decimal point, depending on the model. Analytical balances offer four or more digits to the right of the decimal point. At this level of precision, it becomes necessary to enclose the weighing pan to help eliminate. Sep 13, · Zero point = + div. Change in rest point of balance caused by 1 mg. change in weight = divisions. Substituting in the above equation: Weight equivalent = ( - )/ = mg. ( for ordinary analytical work).
Precision weighing with an analytical balance requires care and alertness on the part of the operator. Many factors can influence the performance of an analytical laboratory balance. Where precision is paramount an error of 0. Influences can be external or internal. Although externally induced errors can be caused by many factors, they are easy to reduce or eliminate.
Usually these causes are traced to lapses in precision balance operating procedures relating to the sample and the laboratory environment. Here are some suggestions on reducing external sources of balance weighing errors. Note that some apply to the balance itself, others to proper handling of samples.
Internally induced errors may stem from improper handling of the balance, overloading it or otherwise damaging the delicate weighing mechanism. In such a case the balance should be returned to the manufacturer for repair by trained technicians.
It may be required daily and even several times a day. In any event calibration should be performed when the analytical balance is relocated or there is a change in the laboratory environment or after a power outage.
Analytical balances such as the Kern models offered by Tovatech can be internally or externally calibrated. For information on this topic please visit our post on calibration.
As a final thought we cannot overemphasize the importance of properly trained personnel when it comes to avoiding balance weighing errors. Analytical balance programming, sample handling, sample placement on the weighing pan and day-to-day maintenance of the analytical balance are key.
Read and follow the operations manual. Contact the scientists at Tovatech for professional advice on selecting and operating a precision analytical balance. Tovatech is a leading supplier of ultrasonic cleaners and other lab or small business equipment. Our staff has a wealth of experience, many of them holding PhDs in various fields. So please feel free to contact the scientists at Tovatech for help choosing equipment or products that fit your needs. We'll send you more information about ultrasonic cleaners, their applications, and how to get the most our of your machine.
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