Electronic enthusiasts provide you with an analysis of the differences and
commonalities between inductors and resistors. What role do resistors play in a
circuit? ,When doing precision electronic design or performing detailed
worst-case ,analysis, we need to consider some parameters that are not
,important in other applications. One of them is the consideration of the
tolerance of the resistor. In fact, no matter whether the resistance value of
the resistor you use is large or small, tolerance must exist. But it does not
limit the maximum and minimum values of resistance in your circuit. Analysis of
the differences and commonalities between inductors and resistors:
Inductors are both passive components. They only work when current passes
through them. Its function is to convert AC into DC, and then filter out part of
the noise waves to allow smooth waves to pass. Currently, the production of
inductors is mainly done by hand and is shielded. The assembly of the inductor
depends on the jig, otherwise the tolerance will be increased. The detection is
mainly through LCR digital bridge or other impedance analyzers, which is divided
into physical testing and environmental testing, which are described in detail
in the previous article. The main parameters of the inductor are: inductance,
current, and resistance. The resistor is usually easily ignored, because the
resistor is an energy-consuming component, and its value has no major impact on
the current. However, as excessive heat is lost, a large amount of useless work
is generated. Some customers will have requirements for resistors. In most
cases, as long as they are not too different, there will be no big impact.
Like inductors, resistors are also passive components. The main physical
characteristic of a resistor is that it converts electrical energy into heat
energy. It can also be said to be an energy-consuming component. The current
passing through it generates heat energy. Resistors usually play the role of
voltage divider and shunt in circuits. For signals, both AC and DC signals can
pass through resistors. Generally speaking, it is easy to judge the quality of a
resistor using a multimeter: adjust the multimeter to the appropriate level of
electrical resistance, and place the two test leads of the multimeter on both
ends of the resistor. Then you can read the resistance from the multimeter.
resistance value. It should be noted that when testing resistance, hands cannot
touch the metal part of the test lead. However, in actual mobile phone repairs,
resistor damage rarely occurs, and except for some resistors in a few models,
little attention is paid to the resistance value of the resistor. Pay special
attention to whether the resistor is soldered or desoldered.
When an inductor is broken down, it becomes a resistor.
What role does a resistor play in a circuit?
When designing precision electronics or performing detailed analysis of
worst-case scenarios, we need to consider parameters that may not be important
in other applications. One of them is the consideration of the tolerance of the
resistor. In fact, no matter whether the resistance value of the resistor you
use is large or small, tolerance must exist. But it does not limit the maximum
and minimum values of resistance in your circuit.
Tolerance: Defines the range of differences between a resistor's actual
resistance and its nominal resistance at the time of manufacture. A resistor
with a nominal value of 1000Ω has a tolerance of ±5%, and the value of the
resistor ranges from 950Ω to 1050Ω. We want this value to be fixed and not
change over time. But this is not the case. Engineers must consider tolerances
in the design and ensure that the designed circuit works within the operating
time limit.
Temperature coefficient: This coefficient describes the phenomenon that the
resistance of the resistor changes with the change of temperature. Its unit is
ppm/K (i.e. 10^-6/K); of course, the same is true if K is replaced by °C as the
unit; usually The temperature coefficient values are 5, 10, 20, and 100. For
example, there is a 1000Ω resistor with a temperature coefficient of 100ppm/K.
When it experiences a temperature change of ±60K (assuming the initial
temperature is 300K and the change range is 240-360K), its resistance value will
change by ±6Ω. Of course, the smaller the temperature coefficient of the
resistor, the higher the price.
Calculation of resistance change and temperature change
The resistor heats itself: For high-precision circuits, sometimes the power
consumption of the resistor must also be considered. Resistors have specific
thermal resistance, whose unit is °C/W. Engineers should be aware of power
losses within a resistor; this will cause the resistor's temperature to rise and
ultimately affect the resistor's resistance.
When determining the maximum and minimum values for the resistors you use,
you must consider tolerances, temperature coefficients, and the effects of
resistor self-heating. When conducting analysis, you may notice that some
parameters can be ignored or not considered accurately, but you must first have
a certain understanding of them before you can determine whether they are
important.
For some precision circuits (such as gain stages in amplifiers), it is
necessary to match the resistors and ensure that their resistances are within
the required range and have the same temperature coefficient.
On some circuits, it is also critical to ensure that certain key resistors
are positioned so that the temperature is the same on both ends of the resistor.
Otherwise, the Seebeck effect also needs to be considered. When using forced air
flow, it is necessary to ensure that the resistor is perpendicular to the air
flow so that heat from one end is not transferred to the other end and the
temperature of the component is equalized.
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