Category: Hardware
In AD7150 capacitance values is increasing and suddenly it starts to decrease and show negative value. What could be the reason behind it?
In AD7150 capacitance values is increasing and suddenly it starts to decrease and show negative value. What could be the reason behind it?
Dear Joan0rtega
Basically, my application is on sensors for humidity measurement. I have 4 copper electrodes, of which two electrodes (C and D) are grounded.
The electrodes A and B are connected to the Cin and Exc pins of the board to measure the capacitance between these two electrodes.
I am using paper with a nanoporous coating as a substrate.
When the relative humidity increases the relative permittivity increases and thus the capacitance increases.
The capacitance is showing an increasing change with increasing RH but after a certain point the capacitance value suddenly starts dropping (although it is in the range and I am using 2pF as input capacitance range) and it settles to a negative value (image attached).
I do not know what this negative value is indicating.
Please help with the same.
Thanks
Sir the CapDac value is zero throughout.
The sensor has 4 electrodes where 2 of which are connected to Cin and Exc that is electrodes A and C (its capacitance is to be noted down) and the remaining terminals are grounded.
The gap between the electrodes is 1 mm (the black space between the electrodes) and the electrode material is copper.
the substrate material is PCB with FR4
