Vietnam or Thailand ? Vote for the TOP Country of the Week !
Updated: May 13, 2025
Every substance which could attack the metal of the balance pan should be weighed upon a watch-glass, and all objects must be dry and cold. A warm body gives rise to air currents which vitiate the accuracy of the weighing. After a weight has been placed upon the pan the beam should be lowered upon its knife-edges, and, if necessary, the pan-arrests depressed.
This is provided for when the balance is set up and very rarely requires alteration. The student should never attempt to change this adjustment. Below the balance pans are two pan-arrests operated by a button from the front of the case. These arrests exert a very slight upward pressure upon the pans and minimize the displacement of the beam when objects or weights are being placed upon the pans.
Before the final determination of an exact weight the beam should always be lifted from the knife-edges and again lowered into place, as it frequently happens that the scale pans are, in spite of the pan-arrests, slightly twisted by the impact of the weights, the beam being thereby virtually lengthened or shortened. Lifting the beam restores the proper alignment.
Then note whether the balance is level; that the mechanism for raising and lowering the beams works smoothly; that the pan-arrests touch the pans when the beam is lowered; and that the needle swings equal distances on either side of the zero-point when set in motion without any load on the pans.
Word Of The Day
Others Looking