Amphenol Noise-Immune NTC Thermistors Provide EMI Solutions

New Tech Tuesdays

Join journalist Tommy Cummings for a weekly look at all things interesting, new, and noteworthy for design engineers.

Published June 7, 2022

Electronic equipment can be susceptible to electromagnetic interference (EMI) if not protected. EMI can cause significant disruptions to electrical equipment like HVAC systems and to the electronics in electric vehicles (EVs). 

The mitigation of EMI in these systems has become an increasingly important safety concern. Fast charging and complex electronic systems, combined with higher component densities all help increase the risks associated with EMI influencing sensor outputs.

Conventional mitigation strategies include:

• Using cable screening
• Adding ferrite cores
• Incorporating twisted-pair wiring
• Employing specialized cable routing

While these solutions can be beneficial in some cases, they can also result in an increase in the cost, weight, or complexity of an EV's battery management systems.

Amphenol Advanced Sensors developed an epoxy-coated, noise-immune NTC thermistor with an integrated RF decoupling function, which provides EMI protection at the component level.

Radio-frequency noise-immunity at the Negative Temperature Coefficient (NTC) sensor element level can mitigate EMI interference over a wide range of frequencies. Noise-immune NTC technology has been validated to international Electromagnetic Compatibility (EMC) compliance standards in industry-leading test facilities.

In this week's New Tech Tuesdays, we'll look at Amphenol Advanced Sensors Noise Immune NTC Type NKI Thermistors.

Noise Immune NTC Type NKI Thermistors

Designing the decoupling capacitor close to the NTC sensor chip ensures the capacitor position is optimized for decoupling EMI even at high frequencies with short wavelengths. Also, integrating the capacitor at the element level enables a drop-in noise immunity upgrade for existing customer temperature-sensing applications. By eliminating or retrofitting shielded cables, cost and weight reduction can be achieved at the system level.

Capacitance values can be chosen to address frequencies of special interest while maintaining the sensor's response time.

NKI noise immune technology can be deployed wherever EMI is present in a system that could cause self-heating of an NTC thermistor, causing incorrect readings or unnecessary fault signals for sensors.

Designers can use them in these applications:

• EV/HEV/PHEV inverter, motor coil, coolant, and battery cell temperature devices
• Combo pressure, coolant/oil, engine, and outside air temperature sensors
• HVAC discharge/evaporator air temperature and automatic defog sensors

Tuesday's Takeaway

As useful as sensors are in a modern vehicle, they do carry concerns when it comes to electromagnetic interference. Conventional NTC thermistor sensors are vulnerable to stray EMI causing self-heating. Amphenol Advanced Sensors' NTC solution mitigates the EMI self-heating effects close to the sensor tip.