DESIGN CONSIDERATIONS FOR AN ELECTROBALANCE MICROFORCE SENSOR

The design of two microforce sensors using the electrobalance principl e and based on commercially available galvanometer units is described in detail. A plausible form for the open-loop frequency response to be expected from optical detection of the position of the meter arm is d erived by analyzing the dynamics of a pivoted beam. The Nyquist criter ion for stability of the feedback circuit necessary to maintain force balance over a specified range of mechanical loads is considered in th e light of ease of manufacture and alignment. With both units, it was relatively easy to achieve zero static compliance and a frequency resp onse of approximately 100 Hz with no resonant behavior. Practical aspe cts of friction, component variation, measurement noise, and temperatu re stability are discussed. (C) 1997 American Institute of Physics.