INA219 battery voltage reading error

[zazas321]

Hello guys. Have anyone got some experience with INA219 voltage and current sensor?I have bought an adafruit prebuilt module and I am getting a voltage error and I am not sure where it is coming from! I have a circuit ( see picture) and I am trying to measure my supply voltage and current. I was using 10V supply but on serial monitor and display I only get about 9.4-9.5V reading. According to the datasheet, INA219 measures the voltage across Vin- to GND. I have measured that voltage with multi meter and I got 9.9 ( which is close enough for me to 10). So if it measures Vin- as it states why the serial monitor reading and LCD display only displays 9.5?

I have also tried using 5V supply and simplified version of the circuit and the reading i get is 4.9 with 40mA current load, as the load current increases, the error increases as well

I have recently bough a 9V alkaline battery to do some testing again and I got the same results:
Battery voltage when no load connected 8.8V
Battery voltage when load is connected 8V
measured voltage across Vin- and GND = 7.95V
Displayed value - 7.5V

 

[kellys_eye]

There is a calibration register in the device. Have you checked out the datasheet to see what facilities there are for calibration?

 

[zazas321]

Do you mean PGA or something else?

 

[kellys_eye]

PGA?? Did you read the datasheet?

Another possibility is that there is a dry solder joint somewhere adding additional resistance where it isn't needed.