Precision resistors are often associated with high-precision resistors, where precision represents the accuracy of the resistance value. In fact, this accuracy is influenced by many factors. These factors that affect the accuracy of resistance are collectively referred to as "stress". Stress comes from many aspects, such as changes in ambient temperature, self heating generated by the resistor itself after being energized, pressure or tension from the PCB, moisture from the external environment, even corrosive gases, as well as factors such as welding, pulses, overload, static electricity, radiation, and so on. All the "stresses" mentioned above will cause changes in the resistance value of the resistor, which means it affects the accuracy of the resistance value. So, what kind of resistor is a precision resistor? The answer is a resistor that combines stability and accuracy.

Why is stability more important than accuracy?

The resistance value of a resistor will be affected by various "stresses" and will change, so it is meaningless to leave the high precision of stability. For example, the precision of a resistor when it leaves the factory is ± 0.01%. We paid a high price for this precision, but after several months of storage or hundreds of hours of load, the resistance value may change by more than ± 300ppm or even more. Another common situation is that the resistor is within the nominal accuracy range during incoming inspection, but after being soldered to the PCB, it exceeds the nominal accuracy range. For example, moisture, static electricity, etc. can cause irreversible changes in the resistance value of the resistor. Stability should be given top priority, rather than pursuing high precision unilaterally.