New MEMS thermal conductivity hydrogen sensors for safety monitoring

Posifa Technologies has released the new PGS1000 series of MEMS thermal conductivity hydrogen sensors. Created for stable, cost-effective safety monitoring in environments where hydrogen is employed and stored, the devices comprise two thermal conductivity dies in a differential configuration — all contained in a compact surface-mount form factor.

These sensors detect hydrogen concentrations in the air by measuring the variation in the thermal conductivity of the gas mixture. This measurement approach offers greater long-term stability and allows a smaller form factor than hydrogen sensors triggered by chemical reactions that ultimately cause the sensor to deteriorate. The company's technology also enables the hydrogen detection capability to be realised at a far lower cost due to the company's highly repeatable, high-volume CMOS MEMS technology.

The series is based on its second-generation thermal conductivity die. The devices provide one die sealed in dry air and acting as a reference, whilst the other is exposed to the gas mixture. This design facilitates an excellent SNR due to common-mode noise rejection and a maximisation of the signal amplification. For safe operation, the sensor is excited with a pulsed waveform (400ms on and 1,000ms off) to minimise the heater temperature.

The sensors are ideal for hydrogen leak detection and monitoring in industrial processes, medical facilities, and automotive fuel cells. For these applications, the devices consolidate fast response times of <1.4s with the broadest available ranges — up to 100% volume — and typical long-term stability of 0.1% F.S/year.