subject: Specifications Of Laboratory Scales [print this page] Specifications Of Laboratory Scales Specifications Of Laboratory Scales
As the name suggests laboratory scales are used in schools or medical universities or scientific labs for research and development. Laboratory scales can be both for physical objects or chemical elements. They are used to measure with extreme precision the weight of an object (or its mass, if very small). Usually they have a beam with an attached pointer, a pivot that is essentially friction less and a measuring arm which has fractional weights. The pointer accounts for deviation from the balanced position. As the weight measurements need to be accurate the pan is usually sealed to keep it free of dust particles and moisture. Samples are kept at room temperature to prevent air from entering and bringing with it pollutants. . Even erroneous readings are part and parcel of laboratory scales. These can be caused by friction, gravitational changes, buoyancy, misalignment, evaporation and condensation and seismic disturbances.
Two basic types of laboratory scales will immediately be recognized by laboratory workers: analytical balances and top-loaders. Analytical balances have weigh pans enclosed and are divided into 2 more types: micro balances (accurate to 1 microgram and semi-microbalances (10 micrograms). Top loaders however weigh objects in pans on top of the instrument and give readings ranging from bottom hundreds of grams to several kilograms with accuracy of 1 mg or 0.1 mg. Top loading balances are convenient and quick but don't secure the objects against wind exposure which may lead to errors.
Laboratory scales have become pretty modern and usually have built-in functions for density computation, part counting, statistical study and other computations. Additional features may come at higher price. You have a choice of color screens and touch screens. Faster microprocessors give accurate readings and better repeatability. Hands-free operation gives convenience and saves time. Multiple interface options for connectivity which includes series, parallel, universal bus service (USB) and wireless. The interfaces should also be able to connect to the printer for readily available hard copy. Similarly regulatory compliances also guide the specifications which are very relevant for medical (pharmaceutical) purposes. Evaluations for laboratory scales come from Ingress Protection (IP), National Electronic manufacturers Association (NEMA), and certification from National Type Evaluation Program (NTEP).
There are various other kinds of laboratory scales. An equal arm balance is the simplest kind of beam balance with a uniform bar suspended at the center. An unequal arm balance is suspended off center. A spring balance has a coiled spring fixed to one end and a hook at the other end where weights are applied. Then there is the moisture balance which is used to calculate the moisture substance in a sample way, hence it needs to be very sensitive to the balance. A platform scale has 2 balances attached on opposite side of beam. Problems in repeatability come from changes in lab environments. Hence, you should go for a lab balance which is ahead by a safety factor of 2 or 3. All balances however have limited memory and data processing capabilities which are solved by wedge' software packages that connect the instrument to the lab network for the purpose of automatic data entry.
