My project aims to measure the current of a photovoltaic module after applying a certain voltage across it.
That means applying a voltage from 0V to 38 V with 0.1V step and measure the corresponding logarithmic currents (which vary from almost 1mA to 8A) then draw the Current-Voltage curve after sending the measured data to the computer.
I have developed an initial system using an Arduino Uno R3 ..... I measured the big voltage across the module using a voltage divider (0V to 40V down to 0V to 5V) and the current was measured by current sensor ACS712. However the current measurements were so bad since it is logarithmic and in the mA range.
My supervisor has suggested that I can't measure such low current and high ones in the same time, and that I have to divide it to 3 ranges. After reading and searching online, I decided to have 3 ranges:
- 4mA to 20 mA using RCV420 (Precision 4mA to 20mA CURRENT LOOP RECEIVER)
- 20mA to 200mA using INA118 instrumentation amplifier with \$0.1\Omega\$ shunt resistance, but I am not sure about the gain and other components that should be implemented in the overall circuit.
- 200mA to 10A using the current sensor ACS712
Am doing the right thing?