Alcohol in blood concentration method - uses device measuring alcohol concentration in breath by differential effect on temperature sensitive resistor

摘要

The device measures alcohol concentration in breath at an instant determined by a timer, the instant being determined by an adjustable time interval beginning within the exhalation period. An error detector monitors the breath flow, and its direction signals the test invalidity when air flow during the above time interval lies below a fixed minimum, or if the air is inhaled. The error detector (327) has a differentiating element (333) and a temperature sensitive resistor (329) in the air flow between a voltage source (331) and the differentiating element (333).