上海充通大学 2.4 Null and Deflection Methods SHANGHAI JIAO TONG UNIVERSITY In a deflection-type device,the measured quantity produces some physical effect that engenders a similar but opposing effect in some part of the instrument. e.g.Fig.2.2 A null-type device attempts to maintain deflection at zero by suitable application of an effect opposing that generated by the measured quantity.Necessary to such an operation are a detector of unbalance and a means (manual or automatic)of restoring the balance. e.g.Fig.2.8 上溶大学 2.4 Null and Deflection Methods SHANGHAI JIAO TONG UNIVERSITY Upper stop -Standord weights top Platt rm assembly of kno yn weight Application of opposing effect Opposing effect produced by measured quantity Fig 2.2 Pressure Gage Fig 2.8 Dead Weight Pressure Gage2.4 Null and Deflection Methods In a deflection-type device, the measured quantity produces some physical effect that engenders a similar but opposing effect in some part of the instrument. A null-type device attempts to maintain deflection at zero by suitable application of an effect opposing that generated by the measured quantity. Necessary to such an operation are a detector of unbalance and a means (manual or automatic) of restoring the balance. e.g. Fig. 2.2 e.g. Fig. 2.8 2.4 Null and Deflection Methods Fig 2.2 Pressure Gage Opposing effect produced by measured quantity Application of opposing effect Fig 2.8 Dead Weight Pressure Gage