OPERATION MANUAL - Scintrex

CElasticHysteresisEffectsAll springs, however elastic, exhibit what is known as elastic hysteresis orstress relaxation effects. This occurs, for example, when the spring length ischanged for a time (by a change in tension on the spring) and then returned toits original tension. When this happens, the spring does not instantaneouslyreturn to its original length, but has a small memory effect, which slowlyrelaxes with time and eventually disappears. The relaxation time may be ofthe same order as the length of time over which its tension was changed. Thefigure on page C-2 shows this effect graphically.When the mainspring in a gravimeter is maintained at a constant length, as itwill be at all times when it is balanced during a measurement, no hysteresiseffect will occur. Between measurements, however, the balance conditionwill usually not prevail, and the spring will be subject to a change in length.Clamping the mass between measurements will fix the spring length but,unfortunately it will not do so precisely at the usual balance condition, so thathysteresis effects are almost certain to occur as a result of clamping. Inaddition, gravimeters with reset mechanisms (e.g. LaCoste & Romberg Dmeter) exhibit elastic hysteresis effects resulting from the change inmainspring tension caused by the reset, even though the mass remains fixedin position.HysteresisC-1CG-5 Manual - part # 867700 Revision 2