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 measure both the high side voltage and DC current draw over I2C with 1% precision.
Most current-measuring devices such as our current panel meter are only good for low side measuring. That means that unless you want to get a battery involved, you have to stick the measurement resistor between the target ground and true ground. Problems arise with circuits since electronics tend to not like it when the ground references change and move with varying current draw. This chip is much smarter as 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 is great for tracking battery life or solar panels.
A precision amplifier measures the voltage across the 0.1 ohm, 1% sense resistor. Since the amplifier 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 (say a 0.01 ohm to measure up 32 Amps with a resolution of 8mA)
We include a 6-pin header (so you can easily attach this sensor to a breadboard) as well as a 3.5mm terminal plug so you can easily attach and detach your load.
Here's the steps on using this product:
- Power the sensor itself with 3 to 5VDC and connect the two I2C pins up to your microcontroller.
- Then connect your target power supply to VIN+ and the load to ground to VIN-.
- Current and Voltage measurement board
- Operating voltage: 3.3V to 5V
- Maximum measurement voltage: +26VDC
- Current measurement range: ±3.2 Amps
- 0.1 ohm 1% 2W current sense resistor
- Current measurement resolution: ±0.8mA resolution
- 0.9" x 0.8" PCB
- PCB (no header or terminal block): 1.9g
- This board/chip uses I2C 7-bit addresses 0x40, 0x41, 0x44, 0x45, selectable with jumpers
- 1 x INA219 High Side DC Current Sensor Breakout
- 1 x 3.5mm terminal plug
- 1 x Straight Pin Header (Male) 1x6 Ways
- Tutorial with Arduino library by Adafruit
- INA219 Arduino Current Sensor Voltmeter Tutorial: Quick Start, by Henry's Bench
- Power Monitoring with an Arduino board and the INA219 sensor, by Marco Schwartz at openhomeautomation
- Arduino Library (Github)