Need modification in capacitance to voltage meter!!!

[angy]

Following circuit is used to measure voltage for capacitor Cx in range of 0.01 uf to 0.1uf.But i want reading for capacitor value 60pf to 150pf.So what changes should be done in the circuit to obtain linear graph b/w capacitor vale and graph

 

[jiripolivka]

The capacitance under 1 nF is barely readable by your circuit. Find a circuit designed for your range. I would use a resonance method with a calibrated variable capacitor substitute.
The are low-cost DVMs with capacitance meters that can measure from units of pF, better than build your own meter.