relative temperature measurment using ad8495

Hello Idan,

Thank you for explaining your circuit. Just to make sure I understand it though, could you please provide a schematic? Please include any other connections that you have around the AD8495.

Could you also describe what you mean when you say the output is wrong? What are you reading out of the AD8495? Are you already trying to sense a temperature through the thermocouples? It would help a lot if you could provide some data for what you are measuring.

Thanks!

Kris

thanks krisf

i made a block diagram which describe what i mean

as I said there are two k type thermocouples which both positive tips are connected . in first amp I measure the absolute temp so the thermocouple A is connected to amp A in the as usually. in second amp I measure the relative temperature between thermocouple B and thermocouple A , i.e  delta_temp = thermocouple_B  - thermocouple_A . for example if both thermocouples are in same temperature , I should measure in amp A the environment temperature and in amp B i should measure 0 deg C temperature or something close to 0 deg C. in fact what I measure is that in amp A  the environment temperature with 1 or 2 degC error and in amp B I measure a temperature of 27 degC no matter what is the environment temperature ( I checked it in two different environments: room temp of 25 degC and the in ice about 0-1 degC). when I placed  thermocouple A in ice and thermocouple B in room temp i got  0 degC reading in amp A and 54 degC in amp B.   

i add the circuit schematic