INA 2126 SenseA pin...

[tanzil_dhk]

Can someone explain me the purpose of Sense A pin in INA 2126 (dual version of INA 126). The pin does not exist in single version.
Only two lines are written in the datasheet and not quite clear to me. I hope someone helps me the purpose and the best use of it.

Thank you

 

[GUMY]

As You can see it from circuit diagram, feedback resistor is not connected internaly to output pin. You have to connect it externaly. This gives You flexibility to wire output and sense pin separately to load and join them there. This can improve accuracy of the circuit.

 

[tanzil_dhk]

As You can see it from circuit diagram, feedback resistor is not connected internaly to output pin. You have to connect it externaly. This gives You flexibility to wire output and sense pin separately to load and join them there. This can improve accuracy of the circuit.

Pardon my ignorence, i can understand that i can connect them externally. but the advantage of connecting externally is not clear to me at all. Please give me an example, of possible....

 

[GUMY]

There is allways some voltage drop from INA output to load. If You connect sense pin directly to load, this voltage drop is compensated.

 

[ZekeR]

The concept is known as a "Kelvin connection," or also a "force and sense" technique. See here. You might drive a load through a resistive connection, in which case the voltage at the op-amp's output won't be quite the same as the voltage at the load (this is the voltage divider effect). However, if you sensed the voltage appearing directly across the load and fed it back into the op-amp, then the op-amp would adjust its output accordingly to get the desired voltage.

This is why bench-top multimeters have a 4-wire ("4W") resistance measurement mode. If you only use the 2-wire ("2W") mode, the smallest resistor you can measure is several mΩ (because your probes have contact resistance which is unpredictable, and in the range of 1mΩ to 100mΩ depending on how hard you press). However, by using the 4W mode you can measure resistors down in the μΩ range.

You might ask, why didn't they add the "sense" pins for the single version? Because they ran out of pins.

 

[tanzil_dhk]

Thanks for the answers....Its very clear now....