Automated Calibration System for Breath Alcohol Analysers
NPL's Breath Alcohol Simulator assesses the performance of evidential breath testing instruments. The system generates a human breath profile with traceable, dynamic concentrations of ethanol. This allows instruments that measure ethanol concentration in exhaled breath to be tested and calibrated. Such instruments in the UK are used to obtain evidence of motorists driving whilst under the influence of alcohol. The system can test the effects of mouth alcohol, alcohol in the dead space of the upper respiratory tract and other dynamic effects.
NPL's Breath Alcohol Simulator conforms to the guidelines set by the Organisation International de Metrologie Legale (OIML) applying to evidential breath testing apparatus.
Application
A programmable sequence of up to 20 samples of each test gas can be presented to each instrument. The ethanol concentration of the test gases have been chosen to suit current UK legislation but can easily be tailored to suit other specific requirements. The test gases are traceable to UK primary gas standards. This ensures accuracy, consistency and international comparability of measurement results.
A typical range of NPL test gases is shown below:
| Test Gas | Ethanol concentration mg/100ml ± 2% relative |
Maximum permissible instrument error ± mg/100ml |
| 1 | 0 | 2.0 |
| 2 | 20 | 2.0 |
| 3 | 35 | 2.0 |
| 4 | 50 | 2.0 |
| 5 | 70 | 3.5 |
| 6 | 105 | 5.2 |
| 7 | 140 | 7.0 |
| 8 | 200 | 10.0 |
The system carries out diagnostic tests to evaluate the effects of the following:
- short term and long term instrument drift,
- memory effects,
- changes in test gas concentration,
- interrupted sample flow,
- changes in sample duration, and
- changes in delivered volume.
An enhanced system is available to deliver humidified breath samples to the test instruments and also to measure their response to other interferent gases such as carbon dioxide.
If you would like further information please contact us.