I have two 10G resistors connected in series with a 3V battery. I want to determine the voltage drop across one of them, which of course is 1.5V. When I use my multimeter to check the voltage drop, it reads ~3mV, which I believe is because it has a 10M impedance so the circuit is really one 10G resistor in series with (a 10G resistor and a 10M resistor in parallel), so the voltage drop when the multimeter is part of the circuit is 2.99 mV.
How can I measure the voltage drop? Is there something I can build so that that I can adapt the multimeter impedance to be high enough that it won't affect the circuit as much?