The readings I am getting off the chip, when converted, are yielding temperatures about 4 deg C higher than every other thermometer/thermocouple probe I own. (AD595 reads 24.5, all others read 20)
Thermocouples are active sensors, that is they generate a low level DC voltage proportional to the temperature. Assuming you have multiple sensors of the same type (J,K,etc.) just read them directly with a good multimeter in it's millvolt range. If one sensor is off compared to the others, then you just have a faulty thermocouple. This could be caused by a faulty weld at the sensor tip, bad connected lead wire, etc.
Thermocouples are not really all the accurate of a temp sensor, their real claim to fame is the very high temperatures they can measure, assuming the sensor's wire insulation used is rated for that high a range.