Now I facing another problem, how do I connect the TIA to the capacitor lead to measure the charging/discharging currents when using 1000V or 1500V or 2000V?
I have found this schematic used by someone to measure this currents but no explanations.
The circuit I made to measure small currents is this: I use : LOG114 with 1uA reference current on input I1. The power supply for the log is made using an 78L05SMD (12V -> 5V) and after the ICL7660 to get the -5V.
The logarithmic output of the LOG114 is scaled to 0V..2.5V and feeded to the 24bit ADC LTC2400.
I use an microcontroller to get the readings and send to computer for further processing.
The problem is how do I connect this to measure capacitor charging/discharging?
If I use for example a simple current source made of a 1.5V battery and a 91Mohm 5% resistor, I get correct readings of current 16nA.
Please help me adapt this to measure charging and discharging of a capacitor.