What’s The Difference?
For professional drivers
With a Semi Conductor Breathalyzer, while the sensor is generally quite accurate around the two calibration points of 0.03% BAC and 0.10% BAC (UK limit 0.08%) the results can be less satisfactory outside of these ranges, and particularly so at lower levels below 0.03%. Needless to say, manufacturers all quote their accuracy as a figure +/- (x)% at the 0.10% level, and while this is generally repeated at this level accuracy does diminish at other measuring points.
A Fuel Cell, on the other hand, measures evenly throughout the range, hence why they are the only types of sensor used for Police grade detectors. Fortunately, while a Police standard detector (such as the Dräeger 6510) costs around £700 there are now several Fuel-Cell based Breathalyzers available at considerably less – the AlcoDigital LifeGuard for instance is just £199 Plus VAT.
The other reason for the price difference is generally down to the sampling method. To get an accurate reading you need an accurate and consistent sample, but whereas the Fuel-Cell type of Breathalyzers also measure exactly 1.7ltrs of air each time (and expel the remainder through an air valve) the semi conductor models use either time alone (say a 3 second blow) or combination of time and pressure.