Thermal EMF in Relays – What It Is and Why Low Thermal EMF Reed Relays Matter - FAQs | Toward Technologies, Inc.

Manufacturer of Opto-MOSFET Solid State Relays, Reed Relays, and RF MEMS Switches. We mainly serve the Semiconductor Testing, ATE, BMS (Battery Management Systems), industrial machinery and Electric Vehicle industries.

Thermal EMF in Relays – What It Is and Why Low Thermal EMF Reed Relays Matter

Toward Technologies, Inc. is a manufacturer of Solid State Relays, Reed Relays and MEMS Switches.

Thermal EMF in Relays – What It Is and Why Low Thermal EMF Reed Relays Matter

Understanding Thermal EMF

Thermal Electromotive Force (Thermal EMF) is a small voltage generated when two dissimilar metals are joined and exposed to a temperature difference. This effect, based on the Seebeck principle, occurs naturally in electronic components and can lead to measurable signal distortion — especially when dealing with microvolt-level precision.

In most everyday circuits, this offset is negligible. However, in sensitive applications like precision test equipment, even a few microvolts of error can significantly affect measurement results.

How Thermal EMF Affects Reed Relays

Reed relays are often used in high-precision systems due to their fast-switching speed, long lifespan, and compact design. But because they contain metallic contact points and internal junctions, they’re susceptible to thermal gradients that generate unwanted voltage offsets.

These thermal offsets can:
  • Disrupt low-level signal integrity
  • Cause measurement drift over time
  • Reduce repeatability in automated testing
  • Increase the need for recalibration and correction

For engineers working with precision instrumentation, choosing a low thermal EMF relay is key to ensuring consistent performance.

TOWARD’s BMF Series: Built for Ultra-Low Thermal EMF Performance

TOWARD’s BMF Series reed relays are engineered for demanding applications where even the smallest voltage offset matters. With measured thermal EMF below 0.5 μV, the BMF Series offers exceptional stability and accuracy for microvolt-level signal switching.

BMF Series | Technical Highlights
  • Thermal EMF:< 0.5 μV
  • Switching Voltage: 200 V
  • Switching Current: 0.5 A
  • Contact Rating: 10 W
  • Contact Resistance:< 150 mΩ
  • Operate Time:< 1.5 ms
  • Release Time:< 0.5 ms
  • Contact Capacitance: 0.5 pF

**Note: Specifications are typical values. For full datasheet details, please consult TOWARD’s technical team

Where Low Thermal EMF Matters Most
  • Digital Multimeters (DMMs)
  • Data Acquisition Systems (DAQs)
  • High-precision laboratory instruments
  • Semiconductor automated test systems
  • Calibration and metrology equipment
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Toward Technologies, Inc - A manufacturer of Solid State Relays, Reed Relays and MEMS Switches.

Located in Taiwan since 1988, Toward Technologies, Inc. is a relay supplier and manufacturer. Main products, including Opto-MOSFET Relays, Opto-SiC MOSFET Relays, Solid State Relays, Reed Relays, And RF MEMS Switches, etc.

B.T supplies relays to the world's semiconductor and automotive industries for over three decades and has long term long-term partnerships with OKITA Works based in Japan; Menlo Microsystems based in California; JEL Systems based in Japan and Teledyne Relays and Coax Switches based in California. Mainly serve the Semiconductor Testing, ATE, BMS (Battery Management Systems), industrial machinery and Electric Vehicle industries.

B.T has been offering customers high-quality Opto-MOSFET and Opto-SiC MOSFET relays since 1988, both with advanced technology and 30 years of experience, B.T ensures each customer's demands are met.