Instrumentation amplifier practical results vs simulation

[nothing909]

I just have a simple question to ask. I'm simulating an instrumentation amplifier and then testing it practically. When I simulate it, my gain is 6, but when I test it, I get a gain of 5.54. I'm just wondering what is causing the slight drop in gain in the practical results?

 

[berkeman]

Homework Statement

I just have a simple question to ask. I'm simulating an instrumentation amplifier and then testing it practically. When I simulate it, my gain is 6, but when I test it, I get a gain of 5.54. I'm just wondering what is causing the slight drop in gain in the practical results?

Can you post the schematic and simulation? And show how you are building and testing the circuit?

 

[nothing909]

I've not got the schematic and simulation to show right now, it's just a basic 3 op amp instrumentation amplifier. do you need them to answer my question and if so, why?

i know the simulation results are ideal, but what factors in a practical test could cause the gain to drop a little?

 

[berkeman]

I've not got the schematic and simulation to show right now, it's just a basic 3 op amp instrumentation amplifier. do you need them to answer my question and if so, why?

i know the simulation results are ideal, but what factors in a practical test could cause the gain to drop a little?

It's just a pretty big error, so I just wanted to see what you did.

Is it this circuit that you posted about over the weekend? https://www.physicsforums.com/threads/testing-instrumenation-amplifier.933232/

 

[nothing909]

yea, that's the circuit.

even if that is a big error, the simulated gain would still be 6 and the practical gain would be slightly lower, why is this?

 

[Tom.G]

Probably the resistors are not exactly matched. Try swapping the R1 resistors and measuring, then swap the R2 and measure, and then the R3.

The table of values you show in Testing instrumenation amplifier indicates there may be some DC offsets of the OpAmps also involved.

edit: fixed spelling typo