There is a design with the AD8293G80 which should be used to measure voltages from 0 to 10 volts. (Input)
The output voltage must be from 0 to 3.3V.
The circuit designed is shown in the following figure.
5V is connected between terminals AN0 + (positive) and AN0- (negative).In the terminals 1 and 8 appear approximately 21 mV which when amplified by 80 must be 1.6 V, but in reality is always present 8 mV, without inporting the input voltageThey are two PCBs of the same prototype with the same problem.Can someone tell me if there is a design error?Thanks
Is the ground of the 5V supply the same as the ground in the circuit?
One thing to check. I notice that AN0_P maps to IN- and AN0_N maps to IN+. Can you check whether applying AN0_P to IN+ and AN0_N to IN- will give you the correct output, as the transfer function on pag 9 of the datasheet is:
Thanks for answering.Yes, the ground is the same for all circuits, but +VS of the OP isn't 5V, I'm working with 3.3V.
As you suggest, I also tried to invert the voltage in AN0+ y An0 -, but the result is the same.
I suspect that Vref may not be equal to 0 and/or the OP can not work with 3.3V.
It would also be likely that the OP is damaged.
Ok, I think I see the problem. While your differential voltage is only 21mV, it is sitting at 2.5V common mode. The amplifier will only work with an input voltage range of 0 to Vcc-1.3, which is 1.6V max for your case. Even if you lowered the common-mode of your input, I think you might still have problems getting this to work.
Can you take a look at the AD8236? You will need to set the gain with a resistor, but I think this will work better for your purposes. You can simulate your conditions with the in-amp diamond plot tool. I put in some initial parameters for you, and you can just adjust based on your parameters. See here.
I hope this helps.
Thanks again for answering.I found this in the data sheet:Which implies that Vref can not be zero or equal to Vs+As it is a prototype, I decided to cut some tracks of the PCB and make some bridges so that Vref is equal to 3.3V and Vs + equal to 5V.And I have measured in pin 6 (VOUT) a voltage somewhat close to what it should be, however in Vadc out the voltage is much lower, I attach a table with the values obtained.I don't understand what it can be. The only thing connected to that pin is the analog input terminal of an MCU (ADC converter).