We are doing a Project to measure a capacitance of range 300nF to 750nF using AD7746.
We are using Capacitance Extension technique to get 200pF and connecting a capacitor of 180pF in series with the capacitance we are measuring (so that effective capacitance can come in the range 180pF).
I have series of doubt while doing this!!!!
1. What will be the Range if capacity extension technique is implemented for 200pF. I think it will be
resolution=200E-12 / 2^24= 1.192092896E-17= nearly 12aF
2. What are the registers value i have to program to activate the capacity extension technique of 200pF.
3. The concept behind the CAPDAC if explained correctly i would be very helpful. ( I really didnt get the concept behind the CAPDAC)
4. The square pulse coming out of EXCA and EXCB is AC or DC??? I mean whether it is Bipolar or Unipolar.
I would be very helpful to solve myself using answers. Expecting your reply.