Ideal components would have no offsets or gain error. The nonideal characteristics of the physical amplifier circuit have introduced a 3 o C error into the measurement. The AD620 datasheet indicates the AD620 has a 125- V maximum voltage offset. The AD620 is available in a tighter grade with a 50- V maximum voltage offset. Resistors must be selected from standard values, they have a resistance tolerance, and they drift with temperature.
Resistors are the cheapest part of the circuit, and they are sloppiest.
Analog Devices supplies the AD620. Another similar and probably superior IA is made by Burr-Brown and is the INA118. Given two gasses at equal pressures, temperatures and an equal volume, the same number of molecules exist in both systems. Essentially, the function goes through the array of numbers swapping adjacent numbers that are in reverse order. The inner loop compares adjacent values, swapping them if they are out of order with respect to each other.