Virtual ground concept in electronic circuit

Question

This is my current sense circuit that I connect to Arduino in order to measure how much current a load draws.

As you can see at the bottom of the image there is a -5 V voltage source connected to the instrumentation amplifier.

The -5 V voltage source I design is this using TLE2426CD.

I get stuck trying to connect that -5 V to the instrumentation amplifier. I try different connections on the simulator but I not get same results as the first picture. I think my problem is in the concept of virtual ground.

Answer 1

The "0V reference" is created by the TLE2426D:

So, initially, to match only your simulation, the power rails would become:

The 0V connection to the input (if needed) can't be determined without knowing more about that you are measuring.

But, according to your text I assume you are powering your arduino from the 12V (which is correct) and not from the TLE2426, and you want your output varying from 0 to 5V according to the power supply. From a previous post, I also assume you need to measure V4 with both polarities. Hence, the INA output, according to the 12 V power supply and your gain and ref:

$$V_4=-50mV \rightarrow V_{INA} \approx 2.25 V$$

$$V_4=50mV \rightarrow V_{INA} \approx 7.25 V$$

Is this correct? If it is, you need to "shift down" the output by 2.25V, and not multiply it by two. You could provide this shift by applying a different reference to the INA, using the op. amp. as a voltage follower connected to a voltage divider.