Induction Charge Detector With Multiple Sensing Stages

NASA’s Jet Propulsion Laboratory, Pasadena, California

Tuesday, January 01 2008 If the readings are analyzed in the time domain, then the use of n detector stages reduces the standard error of the charge measurement, which is proportional to n^–1/2. On the other hand, because of its periodicity, the waveform lends itself naturally to analysis in the frequency domain. The minimum detectable charge can be reduced, in the case of frequency-domain analysis, by increasing the number of available waveform cycles and, hence, by increasing the number of stages.

However, increasing the number of stages without limit does not reduce the frequency-domain minimum detectable charge without limit and does not reduce the time-domain standard error without limit. The reason for this is that increasing the number of stages increases the sensor input capacitance, thereby reducing sensitivity. This obstacle can be overcome by the use of a multiblock sensor assembly, recording the output of each block independently. Each block would comprise a multiple-stage sensor as described above, except that the number of stages (not necessarily 3) would be chosen, in conjunction with other design parameters, to optimize performance.

This work was done by Manuel Gamero- Castaño of Caltech for NASA’s Jet Propulsion Laboratory. For more information contact This e-mail address is being protected from spambots. You need JavaScript enabled to view it .