INA219 1,023V on V-

[ossi]

I have two INA219 Breakout Boards HW-831.
I connect Vcc to +5V and GND to GND.
SDA and SCL are connected.
V+ and V- are not connected.
I measured a voltage of 1.023V with a meter on V- to GND as well as on V+ to GND.
The readout via i2c Bus gives the same voltages.
I think the voltage should be read as 0V.
(The second device have the same result).
Can anyone help me.

[adafruit_support_bill]

With V+ and V- unconnected, the results are undefined. What are the readings when you connect it to an actual circuit?

[ossi]

When I connect a LiIon Cell with +Pin to V- and -Pin to GND.
The voltage on the cell is 4.04V (measured with a meter on the V- Pin to GND of the board).
I get a voltage of 4.012V reading the Register.
So I have to add 0x01c (d28) to the reading of the register to get the same voltage as on the V- Pin.
Next i connected my reference source of 1,0002V.
The readout of the register + the correction gives 1,000V.
I can measure a current of nearly 8uA when I connect the open V- to GND.
Is this in the tollerance of the INA219 ?

[adafruit_support_bill]

I can measure a current of nearly 8uA when I connect the open V- to GND.
Is this in the tollerance of the INA219 ?

What is connected to V+? You can't measure current without a circuit and any current measurement made with one or more connections left floating will be undefined.

The resolution of the device depends on the internal gain setting as described in the documentation. With maximum gain, the resolution is 0.1mA.

https://learn.adafruit.com/adafruit-ina ... -2973528-5

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)

[ossi]

I have read the documentation.
But there is no hint that the V+ and V- can not be unconnected when I measure the bus-voltage.
There is an voltage outcomming of 1.023V at the V- Pin and this is the same as reading the voltage from the register.
Shorting this voltage to GND with a meter gives the current of ca. 8uA.
The final connection is:
V+ connected to GND with a 10 Ohm resistor (measuring the discharge of the cell).
V- connected to the + Pin of a LiIon cell
The measured current is OK
After considering the resistance of the lines, the measured value of the bus-voltage futhermore must be corrected by 28.
But thanks for your help that contributed to the understanding.

[adafruit_support_bill]

But there is no hint that the V+ and V- can not be unconnected when I measure the bus-voltage.

That is not what I said.
* To measure voltage in any meaningful way, at least one of the inputs needs to be connected to something.
* To measure current in any meaningful way, both V+ and V- need to connected in series with your load. Measuring current without a circuit is meaningless.

[ossi]

Everything you write is OK.
Thank you again for your information.
These have been helpful to me and excuse my bad english.