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.
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:
For engineers working with precision instrumentation, choosing a low thermal EMF relay is key to ensuring consistent performance.
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
**Note: Specifications are typical values. For full datasheet details, please consult TOWARD’s technical team
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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