I used AD8231 in our circuit as below picture (For +VS=5.06V supply, with nCS, A0, A1, A2,-VS to GND) , We have some issue when we test AD8231 as below:
1. We tried to short +INA and -INA , the outputA have 2.9mV offset , then I check parameter from AD8231 datasheet , Voso only 30uV , Is it normal?
2.We tried to used differently DC for test conditions then OUTA still has 20mV voltage drop.
Input INA+=30.0mV (DC)with INA-=GND, the OUTA=9.7mV (~20mV drop)
Input INA+=100.1mV (DC)with INA-=GND, the OUTA=79.0mV (~21mV drop)
Input INA+=200.0mV (DC)with INA-=GND, the OUTA=179.1mV (~21mV drop)
Is it normal?
This is one of the most common problem that the customer experience in using instrumentation amplifier. The problem occur because you are running into the diamond plot limits since you don't have enough common mode voltage at the inputs. Please check figure 12, 13 and 14.
We also have FAQ and videos that will explain this in more detail. Please visit the link below:
Lastly, we have this very useful tool that could help you to verify your setup conditions to ensure that you are operating within the specified range of your particular inamp product.
Instrumentation Amplifier Diamond Plot Tool | Analog Devices
Let me know if you need anything else.