Hi Guys,
Customer attends to use our FDC2214 for very low value capacity measurement (0.8~2pF).
The DUT is a special material which only can be driven by 10k~30kHz.
- The sensor excitation frequency FDC2214 supported from 10k to 10 MHz.
- The sensor pin parasitic capacitance is typical 4pF.
Is it a suitable solution for this application?
The formulation illustrated the relationship: Fsensor VS Ltank VS Ctank VS Csensor VS Cin
We got know the C is the parallel sensor capacitance (the sensor pin parasitic capacitance has to be considered), if we try to measure a DUT which has a smaller value 0.8~2pF than Cin, also the Sensitivity is determined by the ratio: Csensor/Ctank.
If the answer is yes, how 's the Ctank value for high accuracy measurement,.
In my opinion, the element accuracy and stability of Ltank VS Ctank also makes negative effect at this measurement, and the Ctank+Cin should be lower than 10 times of DUT (10*[0.8~2pF]) at least.
But the inductance will be ....,
For setting the fsensor at at low excitation range, they have tried to change the Ctank value to 10nF,2.7uF and 4.7uF.
But the resonant tank does not work or the resonant frequency kept rising slowly.
Please provide your opinion on this request.
Best regard!
andy-tan
