The Safety of Sensors, Part 2: Electrochemical

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Vehicles are comprised of many different types of sensors: the fuel gauge measures how much gas is in the tank; the vehicle’s crash sensor provides crucial information to the airbag electronic control unit (ECU) including collision type and severity of impact; and parking sensors alert the driver to obstacles and assist with parking. Most vehicle sensors are designed to keep us safe and an ignition interlock includes a sensor connected to a vehicle’s ignition system designed to prevent the engine from starting if the driver exceeds a specific Breath Alcohol Concentration (BrAC) limit.

As discussed in The Safety of Sensors – Part 1, semi-conductor sensors are sensitive to many environmental changes and as a result require frequent calibration in order to assure operational accuracy. However, most ignition interlocks are outfitted with a more reliable kind of breath sensor: Electrochemical.

Electrochemical sensors measure the electric current created as a result of the chemical reaction from the breath sample provided. The chemical reaction and the resulting current flow through the circuit is a direct indication of the amount of alcohol used during the reaction and the concentration of alcohol in the breath sample. The electric current is measured, converted into data, and displayed to the user either digitally or through LED colour indication. What makes an electrochemical sensor more reliable than a semi-conductor is that the electric current produced is directly proportional to the amount of alcohol in a person’s breath and cannot be fooled by other substances.

Electrochemical sensors are popular with law enforcement breathalyzers and are the standard for all compliance and commercial ignition interlocks.

An ignition interlock consists of two parts: a breathalyzer handset and an Electronic Control Unit (ECU). The handset is affixed to the vehicle dash and is connected to the ECU, which prohibits the vehicle from starting if the driver’s BrAC is over a preset limit.

Ignition interlocks are synonymous the world over with DUI compliance programs, however it’s not uncommon for coaches transporting passengers or school buses transporting children to be outfitted with ignition interlocks. In this case, the interlock represents the companies’ promise to its passengers to make their travel as safe as possible. Moreover, it also promotes and upholds company accountability to the public.

Many industries would benefit from using ignition interlocks, including:

  • Emergency Vehicles (e.g. ambulances)
  • Public Transportation (taxis, subways, buses)
  • Recreational vehicles (snowmobiles and jet skis)
  • Farming (tractors and heavy equipment)

Sensors are all around us, acting as a sixth sense in many ways to keep us safe in a busy world. With the increased use of sensors within a vehicle, including sensors as a part of an ignition interlock system, we will continue to create a safer tomorrow within an increasingly complex and busy world.