Key features of breathalyzers
Units of measurement of blood alcohol
The concentration of alcohol in the body is measured in several ways:
Mg / L – milligrams of ethanol in exhaled air – used in professional devices (sometimes referred to as BrAC – Breath Alcohol Concentration;
Promo – grams of ethanol per liter of blood (g / l) – used widely in personal breathalyzers;
BAC (alcohol concentration in the blood) – gram ethanol per 100 milliliters of blood (g / 100 ml) in 1L of blood contained 10 times 100 ml, i.e. at a ratio of 1.00 per mil = 0.10 BAC;
Concentration in exhaled air is measured in units mikrogramg / l or mg / cubic meter. The conversion of one unit to another is performed at a ratio of 1.00 thousandth = 475 mikrogramg / l = 0.475 mg / cubic meter.
Type sensors for alcohol
The sensor is the main component of any breathalyzer. It converts the blood concentration into an electrical signal. There are three types of sensors – semiconductor, electrochemical and photometric.
In the semiconductor sensor conversion is carried out by combustion of the molecules of ethanol on the heated surface of the sensor.
Electrochemical sensor is of a contemporary generation and conversion is done through chemical processes.
The reaction (process) in electrochemical sensors is carried out at room temperature, while the semiconductor is heated to have hundreds of degrees. Consequently electrochemical sensors compared to semiconductor have a much longer life and devices such sensors consume less energy. Photometric sensor is of the highest class and expensive. Analyze molecules of air exhaled by the photometric method of absorption of light passing through the atmosphere.
All sensors, except for the photometric over time and during prolonged use begin to loose their sensitivity, which reduces the accuracy of the results of the measurements. In order to restore accuracy of breathalyzer it is necessary to perform maintenance (calibration) of the sensor, and in case of full depreciation – of replacing. The calibration sensor is performed using a special device – calibrator. After analysis of exhaled air with this device, breathalyzer was purged with a special mixture and is then configured.
For calibration of each breathalyzer need calibrator and knowledge of the methodology of the procedure. For this reason, the procedure is performed in an authorized service center.
Types of purging
Sampling breath can be held in two ways:
Directly or directly blowing through the mouthpiece, where in the total quantity of the exhaled air passes through the unit. For each new test of hygienic reasons it is necessary to use a new mouthpiece. Even if only one person uses the device mouthpiece is recommended to be replaced every 3-5 tests. In mouthpiece accumulates debris from previous purge may enter the unit and damage it.
Passive purge – when it is not used or a mouthpiece is used or a special funnel-shaped mouthpiece.
The results of the first type are much greater accuracy. This is due to the fact that in the second type there is no direct contact bubbling, the result is influenced by the strength of exhalation, the distance of the lips of breathalyzer, environmental conditions (presence of alcoholic vapors in the air, etc.).
Most mouthpieces are of different shapes and different for the various models are made of non-toxic plastic and not subject to treatment (disinfection).
Non-contact mouthpieces are reusable, can be cleaned and dried before using.
Some breathalyzer a regime of compulsory sampling – when you press a button on the instrument sample is taken from the air. This mode is useful in cases where the person refuses or can not give a sample (for example, if unconscious). The test is performed as follows – the device is placed close to the mouth (nose). The outcome of this passive test is expressed not in numeric and an assessment form – there is alcohol / no alcohol.
Visualization of results
In modern breathalyzers use two basic types of visualization of results;
As digital performance – the result is displayed in decimal form. The main types of displays are LED’s, digital and graphic. The first two types can only play a limited number of characters, the display result is displayed as text or graphics.
By Indicator light – depending on the outcome illuminates the corresponding light indicator for the presence or lack alcohol.
The test result is accompanied by an audible signal and a different alcohol concentration beeper is different.