I have a question about the AD8495. Please take a look at the attachment.
I think it is not out of spec, but I would like to know the cause of these variation.
If I'm understanding correctly, it looks like you are using a precision source to simulate the thermocouple voltage at different temperatures.
Is your setup exactly how it is pictured with testing only one part at a time? Or are you testing all 8 units simultaneously? Are you able to replicate the 25degC data by just grounding the inputs of the AD8495? Have you tried switching out the DC input source?
Do you have a photo of your setup that you could upload?
I can give you the polynomial coefficients to calculate the expected output voltage of the AD8495 for different temperatures and give you an estimate of the expected error. Can you tell me what kind of thermocouple/thermocouples you plan on using? Also, what is the temperature range that you are trying measure? From the first picture I can see the low end is about -25C and the high end is around 300C but I'd like to confirm. Is your reference temperature going to be 32C?
Can you tell me what kind of thermocouple/thermocouples you plan on using?
--> YC105SCK3.2S6U65WX1B3000/Yashimasokki.Co., Ltd. (But no English website.)
Type: K, Class: 2, Temperature Range: 0~300degC
Also, what is the temperature range that you are trying measure?
Is your reference temperature going to be 32C?
--> Our product's ambient temp spec is +5~+32degC, so I tested it at the max ambient temp.
For a measurement temperature range of 0 to 220degC, and using the equation Vout(mV) = a0 + a1*T+a2*T^2+a3*T^3+a4*T^4+a5*T^5+a6*T^6 where T is the measurement temperature:
The error from using this polynomial is about +/-1.5mV over the whole measurement range.
If you are still having issues after implementing this equation, I'd be interested to see the newest data in the plot that you originally sent.
Did you try swapping out the precision source? Do you have a way of measuring what is actually coming out of that source?