When a capacitor is connected to a constant-voltage source through a resistor, the charge on the capacitor increases exponentially. If the source supplies a constant current, however the charge on the capacitor increases linearly. This linear charging principle is used here in the design of capacitance meter which will measure values outside the range of most such meters.
By using a constant-current source, the meter determines the time it takes to match the charge on the unknown capacitor to a known reference voltage. The meter has five full scale range o 1, 10, 100, 1000, and 10,000 uF.on the 1-uF scale , values as small as 0.01 uF can be read easily.
The Circuit
Power Supply
Parts List
PCB Layout
Component Layout
Prototype:
source : Electronic Experimenters Handbook 1980 edition
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