This breakout board will solve all your power-monitoring problems. Instead of struggling with two multimeters, you can just use the handy INA219B chip on this breakout to both measure both the high side voltage and DC current draw over I2C with 1% precision.
With the internal 12 bit ADC (Analog-Digital Converter), the resolution at ±3.2A range is 0.8mA. With the internal gain set at the minimum of div8, the max current is ±400mA and the resolution is 0.1mA. Advanced hackers can remove the 0.1Ω current sense resistor and replace it with their own to change the range (say a 0.01 ohm to measure up 32 Amps with a resolution of 8mA)
· 0.1Ω 1% 2W current sense resistor
· +26V target voltage
· ±3.2A current measurement, with ±0.8mA resolution
· 0.9" x 0.8" PCB
· INA219 chip uses I2C 7-bit addresses 0x40, 0x41, 0x44, 0x45, selectable with jumpers