The INA219 breakout board will solve most of your power-monitoring problems. Instead of struggling with two multimeters, you can just use the handy INA219B chip on this breakout to measure both the high side voltage and DC current draw over I2C with 1% precision. This chip is much smarter - it can handle high side current measuring, up to +26VDC, even though it is powered with 3 or 5V. It will also report back that high side voltage, which is great for tracking battery life or solar panels.
A precision amplifier measures the voltage across the 0.1 ohms, 1% sense resistor. Since the amplifier's maximum input difference is ±320mV this means it can measure up to ±3.2 Amps. With the internal 12 bit ADC, 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 0.1-ohm current sense resistor and replace it with their own to change the range.
INA219 Breakout Module Specs:
- Precision DC Current Sensor up to 3.2A
- 0.1 ohm 1% 2W current sense resistor
- Resolution: 12Bit - ±0.8mA
- Up to +26V target voltage
- Size 22 x 20mm PCB
- This board/chip uses I2C 7-bit addresses 0x40, 0x41, 0x44, 0x45, selectable with jumpers
INA219 Breakout Module Resources:
These breakout boards are ideal for projects like solar circuits, battery-reliant projects, or modules that need precise power despite a less-than-reliable supply. And while many people may argue that a multimeter is more than capable of performing this task, multimeters are expensive and designed to be used in short bursts, whereas these can be permanently integrated into projects to offer a “Live Feed” of sorts directly to your computer, Arduino board, or any other reader or display unit in order to keep a log of the readings or react accordingly as a problem arises.
Although it does what is says in the specifications, there are a number of things you need to be aware of so make sure you do a bit of Googling for the various implementations first:
1. To be able measure both current and voltage, the wiring needs to be done exactly right.
2. The setting of the variables that are being used to calibrate/message the device are also quite important, especially when you are running a current close to it's max.