KT503R2 Equivalent & Substitute Parts

Part Overview

The KT503R2 is an NTC thermistor manufactured by Littelfuse Inc., featuring a 50kΩ resistance at 25°C with a B value of 4140K. This component is classified as a temperature sensor in bead form with epoxy packaging and is currently listed as obsolete. Due to its discontinued status, identifying functionally equivalent substitute parts is essential for ongoing system maintenance, repair, and new design implementations where this thermistor specification is required.

Substiute Parts

KT503R2

Littelfuse Inc.In Stock: 895KT503R2 Datasheet

Current PartRFQ

192-503QET-A01

Honeywell Sensing and Productivity SolutionsIn Stock: 2155192-503QET-A01 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the KT503R2 is determined by the following critical parameters:

• Resistance Value: 50kΩ at 25°C (primary electrical characteristic)
• B Value: Thermal response characteristic (4140K nominal range acceptable)
• Lead Wire Length: 1.50" (38.00mm) for mechanical fit
• Package Type: Bead configuration for form factor compatibility
• Operating Temperature Range: Must accommodate the application's thermal requirements
• Compliance Standards: RoHS and REACH compliance for regulatory alignment

The substitute part 192-503QET-A01 meets these criteria with matching resistance, comparable B value, identical lead length, and equivalent bead packaging.

Parameter Comparison

Engineering Selection Recommendations

The 192-503QET-A01 from Honeywell Sensing and Productivity Solutions is a direct functional equivalent for the obsolete KT503R2. Selection is based on the following factors:

• Electrical Equivalence: Both components maintain 50kΩ resistance at 25°C with B values within 2K of each other (4140K vs. 4138K), ensuring thermal response compatibility.
• Mechanical Compatibility: Identical lead wire length (1.50") and bead package form factor enable direct mechanical substitution.
• Thermal Performance: The Honeywell substitute provides an extended operating temperature range (-60°C to 150°C) compared to the original (120°C maximum), offering broader application flexibility.
• Regulatory Compliance: Both components meet RoHS and REACH requirements, ensuring compliance with current environmental standards.
• Availability: The substitute part is currently in active production with confirmed inventory, eliminating supply chain risk associated with the obsolete original.

Frequently Asked Questions (FAQ)

Q: Can the 192-503QET-A01 be used as a direct replacement for the KT503R2?

A: Yes. Both components share identical resistance values (50kΩ), comparable B values (4140K vs. 4138K), matching lead lengths (1.50"), and equivalent bead packaging. The substitute is mechanically and electrically compatible for direct substitution.

Q: What is the significance of the B value difference (4140K vs. 4138K)?

A: The B value defines the thermistor's thermal response curve. A 2K difference represents a 0.05% variance, which is negligible for most temperature sensing applications and falls within acceptable tolerance for thermistor performance.

Q: Does the extended operating temperature range of the substitute affect compatibility?

A: No. The substitute's extended range (-60°C to 150°C) encompasses the original's maximum operating temperature (120°C). Applications operating within the original specification will function identically with the substitute.

Q: Are there packaging differences between the two parts?

A: The original specifies "Bead, Epoxy" while the substitute specifies "Bead." Both are bead-form thermistors with equivalent mechanical properties and mounting characteristics for this application.

Q: What compliance certifications apply to both parts?

A: Both the KT503R2 and 192-503QET-A01 are RoHS compliant and REACH unaffected, meeting current environmental and regulatory requirements for electronic component use.