Analysis of common detection methods and influencing factors of resistors

Date：2022-06-24 15:59:24Views：766

The normal use of the circuit is often inseparable from the resistor. If the resistor is not good, it will directly affect the normal use of the later circuit to a certain extent. Therefore, in order to ensure the normal use of the circuit, we must pay attention to the detection of resistors. So what are the detection methods for resistors? Let's have a look.

1. Check with a pointer multimeter

During detection, first turn the gear knob on the pointer multimeter (hereinafter referred to as the multimeter) to the appropriate "Q" gear according to the resistance value of the resistor. After the measuring gear is selected, it is also necessary to zero the resistance deflection of the multimeter. Short circuit the two probes of the multimeter to each other, and turn the "zero adjustment" knob so that the probe points to the "0" position (full scale) of the resistance scale. Special attention should be paid to that every time the gear is changed during the measurement, the gear should be reset.

Connect the two probes (positive and negative) of the multimeter with the leads at both ends of the resistor to be measured, and the probe should point to the corresponding resistance scale. If the meter needle does not move, the indication is small and stable, or the indicated value differs greatly from the indicated value on the resistor, it indicates that the resistor is damaged. When measuring a resistor with a resistance value of more than tens of kiloohms, be careful not to touch the leads at both ends of the resistor at the same time, so as to avoid measurement error caused by the resistance connected to the human body.

2. Test with digital multimeter

The digital multimeter does not need to calibrate zero before measuring the resistor. Turn the gear knob to the appropriate "O" gear and turn on the power switch to measure.

When selecting the measuring gear, try to make the display screen display more effective numbers. For ordinary measuring resistors below 200 Ω, select "200 Ω" gear, and for 200 ~ 1999 Ω resistors, select "2K Ω" gear, 2 ~ 19 99K Ω, the resistor can select "20kq" gear, 20 ~ 199 The 9K Ω resistor can be in "200K Ω" gear, and the 200 ~ 1999k Ω resistor can be in "2m Ω" gear, 2 ~ 19 The 99mq resistor can be in "20m Ω" gear, 20 ~ 199 "200m Ω" gear can be selected for 9m Ω resistor. Resistors above 200m Ω cannot be measured because they have exceeded the maximum range (take dt890b digital multimeter as an example).

During measurement, two probes (positive and negative) are respectively connected to both ends of the measured resistor, and the LCD display screen will display the resistance value of the measured resistor R. If "000" (short circuit) appears, only the highest position shows "1" (open circuit), or the displayed value differs greatly from the marked value on the resistor, it indicates that the resistor is damaged.

Influencing factors:

1. Length: when the material and cross-sectional area are the same, the longer the length of the conductor, the greater the resistance.

2. Cross sectional area: when the material and length are the same, the smaller the cross sectional area of the conductor, the greater the resistance.

3. Material: when the length and cross-sectional area are the same, the conductor resistance of different materials is different.

4. Temperature: for most conductors, the higher the temperature, the greater the resistance, such as metal; For a few conductors, the higher the temperature, the lower the resistance, such as carbon.

The resistance of the conductor has nothing to do with whether the conductor is connected to the circuit, whether there is current in the conductor, the size of the current and other factors. The resistivity of superconductors is zero, so the resistance of superconductors is zero. The content introduced above is the detection method of resistor. Of course, there are many ways to detect the quality of resistors, so we can also choose the appropriate detection method according to the actual needs.