Espeasy mega right formula for INA219 current

[planedo79]

Hi,

I have an Ina219 and a wemos d1 mini. I got done the correct wiring and and the sensor gets the current value. I measure the battery current. However, the value is incorrect. The multimeter gives a higher value than ina219. Is there any syntax espeasy formula line with which I could get calibrated to the correct value and what variables are needed for syntax? % value% + 0.130 Is this correct or can it be written in a more professional way?

Newbie question I guess..

[TD-er]

You can apply the calibration in the formula field and indeed it is probably something like this:

Code: Select all

%value% + 0.130

As advice.
Try to measure a few currents with both the multimeter and the INA219 in series and see if it is a constant offset.
I would expect the offset to be linear, and not a simple offset.
So more something like this:

Code: Select all

%value% * 1.05

(5% as a random example)
The used shunt does have a tolerance so I would expect you should only correct for that tolerance. A constant offset is not something I would expect.

[ThomasB]

A 130mA offset seems excessive for the circuit shown in the photo. As a sanity check, please provide the measurement's variation when you compare the DMM's reading to the INA219A.
Meter = ? mA (in series with battery lead, input of Vreg)
INA219 = ? mA

Be sure to record the INA219A current while the DMM is still wired in series with the battery.

- Thomas

[TD-er]

Well, if the leads in the photo are used to draw a (significant) current, then I guess the voltage has dropped significantly when it arrives at the consumer.
If that consumer is a resistive load, then the measured current can be quite a bit lower.

So make sure (as also said by Thomas) to measure the current with both the multimeter and the INA219 in series.
Otherwise it is impossible to find a proper calibration offset.

[Wiki]

...and never ever try to calibrate a voltage/current sensor using a breadboard and think your results would be reliable - it will be an endless story. Take the readings at the momen as they are. Calibration of voltage/current readings only makes sense in a ready soldered circuit, believe it.

But nevertheless, playing around with a breadboard following the suggestions of ThomasB and TD-er is a pretty good practice for a lateron following reliable calibration.

[dynamicdave]

I've just lashed up a INA219 with a Wemos D1 Mini (FW=mega-20191003) and get correct readings

I've got a 330 ohm resistor across the 3v3 rail (so the current should be 10mA).

As you can see from the screen-shots the current is 10mA.

The only differennce I can see is I'm using a "Measure range" of 16V, 0.4A

PS:
I've just flashed the Wemos with mega-20200410 and the INA219 gives correct readings on all settings,
so it might be worth trying that.

ScreenShot027.png (32.02 KiB) Viewed 14229 times

ScreenShot026.png (19.1 KiB) Viewed 14229 times

[planedo79]

...and never ever try to calibrate a voltage/current sensor using a breadboard and think your results would be reliable - it will be an endless story. Take the readings at the momen as they are. Calibration of voltage/current readings only makes sense in a ready soldered circuit, believe it.

But nevertheless, playing around with a breadboard following the suggestions of ThomasB and TD-er is a pretty good practice for a lateron following reliable calibration.

Yes, I think it was the case here. No after I soldered all parts /wiring it seems the values are right. Thank you for support.

[planedo79]

I've just lashed up a INA219 with a Wemos D1 Mini (FW=mega-20191003) and get correct readings

I've got a 330 ohm resistor across the 3v3 rail (so the current should be 10mA).

As you can see from the screen-shots the current is 10mA.

The only differennce I can see is I'm using a "Measure range" of 16V, 0.4A

PS:
I've just flashed the Wemos with mega-20200410 and the INA219 gives correct readings on all settings,
so it might be worth trying that.

ScreenShot027.png
ScreenShot026.png

Thank you for information, I will give it a try.

[planedo79]

A 130mA offset seems excessive for the circuit shown in the photo. As a sanity check, please provide the measurement's variation when you compare the DMM's reading to the INA219A.
Meter = ? mA (in series with battery lead, input of Vreg)
INA219 = ? mA

Be sure to record the INA219A current while the DMM is still wired in series with the battery.

- Thomas

I think it was too this wires and loose connections. After soldering values changed close to the DMM readings. Thanks.

[planedo79]

I made few changes (battery voltage I measured from wemos A0 pin, and INA219 sensor is for solarpanel current reading), and I got it running now. Thanks all!
(Added some pictures if someone is interested doing similar project)