Sophisticated sensors

All GSS sensors use a technique called non‐dispersive infrared (NDIR) sensing where light is injected into the optical measurement chamber, which contains the gas of interest. The light that passes through the optical cavity is detected by the photo diode. The signal from the photo‐diode is digitised by the microcontroller and compared with a reference level stored in memory. The microcontroller can then calculate the level of CO2 in the optical measurement chamber.

The power consumed by the CO2 sensor depends on several interrelated factors. The type and efficiency of the light source is the largest contributor to the power consumed by the sensor. In comparison to many other sensors that use incandescent light sources, GSS sensors use a highly efficient LED to illuminate the CO2 gas. LEDs can (but are not always) be much more efficient in converting electrical power into light than conventional light sources.

The length of time the light source is active is also a major contributor to how much power is consumed by the sensor. The light source in a CO2 sensor can be run continuously or pulsed to minimise overall power consumption.

Today’s semiconductor devices consume much less power than their forebears due to lower supply voltages, effective power  management and shrinking feature sizes. Nevertheless, improvements to signal processing strategies for filtering, data handling and communications can improve power savings.

A recently published application note describes the fundamentals that underpin the low power design of GSS sensors and how to calculate the power consumption of each device. Finally, strategies for reducing power consumption whilst optimising overall performance are presented, including the new CozIR‐Blink sensor.

Recent Issues