MicroAmps and the INA169
Moderators: adafruit_support_bill, adafruit

MicroAmps and the INA169

by soccerjmp on Sun Mar 03, 2013 3:26 pm

Hi all!

I am simply trying to measure the current that is flowing from a solar panel. I just purchased the INA169 current sensor from adafruit and was attempting to verify its functionality. Below is a schematic of what I am attempting to do. I just want the current flowing through the resistor. I know that it should be reading (5/1000) = 5mA. I am using the analog read for the signal input. This value fluctuates between 1 and zero. I have tried to Fmap the analog read and manually calculating the value ( 5 * AnalogSignal)/1023 . I simply want the serial com. to display the current. Any Ideas? THANKS
Untitled.png (16.55 KiB) Viewed 546 times
Posts: 1
Joined: Sun Mar 03, 2013 3:13 pm

Re: MicroAmps and the INA169

by adafruit_support_bill on Sun Mar 03, 2013 3:41 pm

The default output is 1v/A. So for 5mA, the output should be .005v. Since the Arduino A/D is 10 bits, using the 5v default analog reference, a 5v signal will give you a raw reading of 1023. A 0.005v signal will give you a raw reading of about 1. Exactly what you are seeing.

To get more resolution at for reading smaller currents, you need to increase the load resistance (default is 10K) and/or use a lower analog reference voltage. Doubling the load resistance will give you twice the resolution. Halving the reference voltage will do the same.

Another option is to go to a higher resolution A/D such as the ADS1115 : http://adafruit.com/products/1085

Posts: 37644
Joined: Sat Feb 07, 2009 10:11 am

Re: MicroAmps and the INA169

by dboechler on Fri Mar 14, 2014 10:38 am

If your circuit drawing is acurate you have the current sense resistor in the wrong place. It should be across the VIN+/-

You have it down stream..
Posts: 1
Joined: Fri Mar 14, 2014 10:35 am