Color problem of resistance used in circuit board welding;

Khaki is generally carbon resistance, which is the most economical and practical resistance. Carbon resistor is not a precision resistor, so it is generally 3-color ring /4-color ring. The error loop of 4-color loop is generally gold (5%) and silver (10%). Resistance with colorless error ring is commonly known as trichromatic ring resistance (error ring is colorless, representing 20% error).

Blue is generally a precision resistor (such as metal oxide film resistor), but the four-color ring resistor is also blue. Judging whether a resistor is a precision resistor can be known by the number of color rings.

Generally, the numerical value printed on PCB is the direct nominal resistance below 1Kω, the direct nominal value above 1K is k, and the nominal value above 1000K is m (megaohms), which is the largest unit. Only the resistors below10mΩ will be used in general circuits.

If individual circuits (such as feedback) need to use precision resistors, J will be added after the resistance value. For example, the precision resistor is labeled as 1kω. But in the later debugging and improvement of the product, it may be necessary to change the resistance. The engineer has the final say on how much resistance to use and what resistance to use. Because PCB will not be changed after it is finalized (it will cost money to change), so don't take PCB as the standard, or it will make a joke.