An analytical balance (or lab balance) is a class of balance designed to measure small mass in the sub-milligram range. The measuring pan of an analytical balance (0.1 mg resolution or better) is inside a transparent enclosure with doors so that dust does not collect and so any air currents in the room do not affect the balance's operation. This enclosure is often called a draft shield. The use of a mechanically vented balance safety enclosure, which has uniquely designed acrylic airfoils, allows a smooth turbulence-free airflow that prevents balance fluctuation and the measure of mass down to 1 μg without fluctuations or loss of product. Also, the sample must be at room temperature to prevent natural convection from forming air currents inside the enclosure from causing an error in reading. Single pan mechanical substitution balance is a method of maintaining consistent response throughout the useful capacity of the balance. This is achieved by maintaining a constant load on the balance beam and thus the fulcrum, by subtracting mass on the same side of the beam as which the sample is added.
Electronic analytical scales measure the force needed to counter the mass being measured rather than using actual masses. As such they must have calibration adjustments made to compensate for gravitational differences from changing locations and altitudes. They use an electromagnet to generate a force to counter the sample being measured and output the result by measuring the power (and resulting force) needed to achieve balance. Such a measurement device is called an electromagnetic force restoration sensor.
A Triple beam balance is an instrument used to measure mass very precisely. The device has reading error of +/- 0.05 gram. The name refers to the three beams including the middle beam which is the largest size, the front beam which is generally a medium size, and the far beam which is generally the smallest size. The differences in the size of the beams indicates the difference in weights and the reading scales that each beam carries. The reading scale can be enumerated such that the middle beam reads in 100 gram increments, the far beam can read from 0 to 10 grams, and the front beam can read in 10 gram increments. The parts of a triple beam balance are identified as following:
Before using a triple beam balance, the scale pointer should be at zero. The zero adjustment knob can be used to adjust the scale pointer. Place the objects on the pan and adjust the riders until the scale pointer is at zero again, and then sum the weights marked (e.g. the 4th notch of 100 gram beam is 400g) to find the weight of the sample.
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