For many laymen, there is a difference between high-precision resistors and ordinary resistors. It has similar appearances. What is the difference between high-precision resistors and them? High-precision resistors can be considered as a special resistor with high precision, high accuracy, and low error.

The temperature change has the greatest influence on the resistance, and is generally expressed in ppm/°C in the temperature coefficient of resistance, that is, the temperature change of 1 degree corresponds to a change in resistance of a few parts per million. 100ppm/°C is 0.01%/°C. This temperature coefficient has 1PPM, 5PPM, 10PPM and so on in precision resistors, and some even reach lower requirements.

The degree of aging of the resistor, we usually think of the long-term stability of the resistor, generally expressed in ppm / year, also expressed in % / year. Although the accuracy of the resistor is high when it leaves the factory, if it ages with time, it will change very quickly, and such a resistor will lose its high accuracy. 
 
The initial adjustment error of the precision resistor is not very important for the common resistor. Usually, it is only necessary to know the resistance deviation. However, this parameter is also very important for the precision resistor. On many high-precision instruments, the deviation of the resistor is required to be very small.

The above three points are the standards for measuring precision resistors. The requirements for precision resistors in aerospace, military and instrumentation are very strict. In many cases, it is necessary to purchase precision resistors with reference to high-precision, high-accuracy, and low-error technical parameters.