The Safety of Sensors, Part 1: Semi-conductors

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Micro Cell Sensor

Sensors keep us safe in many different ways: a push-button activates a crosswalk, a radar gun detects speeding drivers, a traffic light turns green to guide us through a busy intersection. Some sensors improve the quality of life; others help save lives.

The primary purpose of a sensor is to discover subtle changes within an environment. These changes can be tactile through a finger touching a screen, audible through sound bouncing inside a microphone, or even chemical through the composition of breath alcohol.

Since the invention of the automobile, breathalyzer technology sits at the forefront of traffic safety and drink-driving rehabilitation. In fact, the first breathalyzer didn’t house a sensor; instead, it used a chemical solution that changed colour depending on the level of the driver’s intoxication. This concept stayed the norm until 1954, when Professor Robert F. Borkenstein created the Breathalyzer, the first ever breath alcohol tester with a sensor inside.1

Inside every modern breathalyzer and alcohol interlock handset is a sensor; it’s one of the most important parts of the breath testing device. The sensor breaks down the alcohol molecule into several pieces, some of which are electrons. The number of electrons present in the sample are equal to the number of alcohol molecules. The alcohol molecules are then converted into a quantitative value and displayed either digitally to the user or through LED colour indication. The end product is the Breath Alcohol Content (BrAC) result.

Semi-conductor sensors force the breath sample to come into contact with a metal conductor. The alcohol changes the conductor’s electrical resistance—the ease or difficulty of how the electric current passes through—and is then converted into the breath test result.

The Good:

  • Long shelf life
  • Cost-effective
  • More effective for detecting lower concentrations
  • Typically smaller in size
  • Wide temperature range

The Bad:

  • Requires monthly calibration
  • Can be fooled by other substances other than alcohol
  • Sensitive to humidity
  • Shorter performance life
  • Large margin of error

Whether in a car, on the streets or in your home, sensors are all around us, guiding our decisions towards a safer lifestyle.


1 “Breathalysers in History.” DrinkDriving.org, 2015. Web. 23 Nov. 2015.