As the individual resistive elements of ACAS series components are thermally coupled by the shared alumina substrate, even heat distribution across the entire resistor array is achieved. For resistors, the temperature of the resistive element determines the magnitude of the resistive drift over time. Due to this inherent thermal coupling, the resistors of the array will drift together at virtually the same rate even though the individual resistor elements are under different load conditions. Consequently, the relative resistive drift of the ACAS array's resistance ratio is extremely low, specified at a maximum of ±0.05% after 1,000 hours considering the precision power operation mode power rating from the ACAS precision series, and it is typically much smaller. If tolerance tracking and TCR matching specifications are not a requirement, then the ACAS professional series version which is offered only with absolute tolerance and absolute TCR specifications can be considered.