Technical Article: Cylindrical Fixed Resistor

Cylindrical fixed resistors, also known as Metal Electrode Face Bonding Type (MELF) resistors, are available in three main types: carbon film ERD type, high-performance metal film ERO type, and 0Ω resistors for bridging. Compared to surface mount resistors, MELF resistors are non-directional and reversible, easy to package and use, have high assembly density, and exhibit high bending resistance when fixed to printed circuit boards. They also have relatively low noise levels and third harmonic distortion, making them commonly used in high-end audio and electronic products.

① Structure: MELF resistors are made by coating a high-alumina ceramic substrate with a metal or carbon film, pressing metal cap electrodes at both ends, adjusting the resistance value using a threaded groove method, sealing the surface with heat-resistant paint, and finally marking the resistance value with color codes. ② Performance: The main technical characteristics and ratings of MELF resistors are shown in Table 6-5. Table 6-5 Main Technical Characteristics and Ratings of MELF Resistors

model

project

Carbon film

metal film

ERD-21TL

ERD-10TLO

(CC-12)(0Ω)

ERD-25TL

(RD41B2E)

ERO-21L

ERQ-10L

(RN41C2B)

ERO-25L

(RN41C2E)

Operating ambient temperature (°C)

-55～+155

-55～+150

Rated power consumption (W)

0.125

Maximum rating

Current 2A

0.25

0.125

0.25

Maximum operating voltage (V)

150

300

150

Maximum overload voltage (V)

200

600

200

300

500

Nominal resistance range (Ω)

1～1M

≤50mΩ

1～2.2M

100～200K

21～301K

1～1M

Tolerance for resistance value (%)

(J±5)

(F±1)

Temperature coefficient of resistance (10⁻⁶/℃)

-1300/350

±10

±100

Weight (grams/1000 pieces)

③ Marking Identification: The resistance value of MELF is indicated by color ring marking.

(3) Chip Potentiometer: Surface mount potentiometers, also known as chip potentiometers, include various types such as chip, cylindrical, and flat rectangular structures. They are used to adjust the voltage and resistance of circuit components, hence they are respectively called voltage divider potentiometers and variable resistors.

4. Structure Surface potentiometers come in four different shapes: open structure, dustproof structure, fine-tuning structure, and fully sealed structure.

② Performance

a. Nominal resistance range: 100～1MΩ

b. Tolerant resistance range: ±1% 5%

c. Resistance law: Linear

d. Contact resistance change: 3% or 3Ω

e. Resolution: Infinite

f. Resistance temperature system 25010-6/℃

g. Maximum current 100mA

h. Operating temperature range: -55℃ to +100℃

i. Rated power consumption series: 0.05W, 0.1W, 0.125W, 0.2W, 0.25W, 0.5W

③ External Dimensions: The surface potentiometers are available in Type 3, Type 4 and Type 6 models. Their external dimensions are shown in Table 6-6.

Table 6-6 External Dimensions of Chip Potentiometers

model

Size (mm)

Type 3

33.22

331.6

Type 4

3.84.52.4

44.51.8

452

44.52

4.552.5

44.52.2

Type 6

664

Ф64.5

Reprinted from the website of Wuhan Xingtongli Power Technology Co., Ltd.