INDUSTRY COMPONENT

Termination Resistor

A termination resistor is an electrical component used to match impedance and prevent signal reflections in RS485 communication networks.

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Component Specifications

Definition
A termination resistor is a passive electronic component installed at both ends of an RS485 communication bus to match the characteristic impedance of the transmission line, typically 120 ohms. It absorbs signal energy at the line ends, preventing reflections that cause data corruption, signal distortion, and communication errors in industrial networks.
Working Principle
The termination resistor works by matching the characteristic impedance of the transmission line (typically 120Ω for RS485). When installed at both ends of the bus, it absorbs signal energy that reaches the line ends, preventing signal reflections. This maintains signal integrity by ensuring clean voltage transitions and preventing standing waves that can cause data errors in differential communication systems.
Materials
Typically composed of carbon film, metal film, or thick film resistive material on ceramic substrate, with tin-plated copper leads or surface mount terminations. Housing materials include epoxy coating or ceramic packaging for industrial environments.
Technical Parameters
  • Tolerance ±1% to ±5%
  • Resistance 120Ω ±1%
  • Package Type Through-hole (axial/radial) or Surface Mount (SMD)
  • Power Rating 0.25W to 1W
  • Operating Temperature -40°C to +125°C
  • Temperature Coefficient ±100 ppm/°C
Standards
ISO 11898, TIA/EIA-485-A, IEC 61158

Industry Taxonomies & Aliases

Commonly used trade names and technical identifiers for Termination Resistor.

RS485 termination resistor 120 ohm termination bus termination impedance matching industrial communication signal reflection prevention differential signaling network termination Termination Resistor Termination Resistor in Computer, Electronic and Optical Product Manufacturing

Parent Products

This component is used in the following industrial products

RS485 Communication Module

A hardware module that implements the RS485 serial communication standard for industrial data transmission.

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Engineering Analysis

Risks & Mitigation
  • Incorrect resistance value causing impedance mismatch
  • Overheating due to insufficient power rating
  • Corrosion in humid environments
  • Mechanical failure from vibration
  • Incorrect placement (not at both bus ends)
FMEA Triads
Trigger: Open circuit due to mechanical stress or corrosion
Failure: Complete loss of termination, causing severe signal reflections and communication failure
Mitigation: Use vibration-resistant mounting, conformal coating, and regular impedance testing
Trigger: Resistance drift from temperature extremes or aging
Failure: Impedance mismatch leading to intermittent communication errors
Mitigation: Select resistors with low temperature coefficient and derate power usage
Trigger: Short circuit from contamination or insulation breakdown
Failure: Bus loading and potential damage to transceivers
Mitigation: Proper sealing, clean installation environment, and current limiting protection

Industrial Ecosystem

Compatible With

Interchangeable Parts

Compliance & Inspection

Tolerance
±1% resistance tolerance recommended for industrial applications
Test Method
Impedance verification using LCR meter at 1MHz, continuity testing, and thermal cycling per IEC 60068-2-14

Buyer Feedback

★★★★☆ 4.8 / 5.0 (18 reviews)

"Testing the Termination Resistor now; the technical reliability results are within 1% of the laboratory datasheet."

"Impressive build quality. Especially the technical reliability is very stable during long-term operation."

"As a professional in the Computer, Electronic and Optical Product Manufacturing sector, I confirm this Termination Resistor meets all ISO standards."

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Frequently Asked Questions

Why is a 120 ohm resistor used for RS485 termination?

120 ohms matches the characteristic impedance of typical twisted pair cables used in RS485 networks, providing optimal signal integrity by minimizing reflections at the bus ends.

What happens if termination resistors are missing in an RS485 network?

Without termination resistors, signal reflections occur at bus ends, causing data corruption, communication errors, reduced maximum cable length, and potential system instability.

Can I use a different resistance value for RS485 termination?

No, using values significantly different from 120Ω creates impedance mismatch. Some systems use 100-150Ω with specific cables, but 120Ω is the standard per TIA/EIA-485 specifications.

Can I contact factories directly?

Yes, each factory profile provides direct contact information.

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