Manual / automated capacitance box using micro-controller technique

A capacitance box contains more than one decade capacitance. These decades have different capacitance ranges to get a much wider range of the capacitance steps obtained by the whole box. In general, a decade capacitance is constructed by ten capacitors to give ten manual capacitance steps. In this paper, a new design of a capacitance box is presented using two-decade capacitances. Each one of them is constructed by four capacitors only. This capacitance box is automatically controlled by especially designed programs using the Lab VIEW to provide a combination of 100 sequential capacitance steps from the common output of the two decades. These capacitance values can be used for the automatic calibrations of the capacitance measurement devices. Also, its capacitance steps can be obtained by manual way according to the user requirements, through an assembly language program using push-button switches. Control of each decade in this box depends on a micro-controller technique and four electronic relays as clearly investigated in this paper. Practical design, fabrication, and calibration for one decade of the capacitance box have been demonstrated in details through this research. The second decade in this box is the same as the first one, but it has different value of the capacitance per step.