Method and device for testing the measuring function of a measuring device

A method for testing a measuring function of a measuring device for measuring nitrogen monoxide in a sample of exhaled breath, the measuring device including a first part having a gas sensor for measuring nitrogen monoxide that generates at least one output signal and a second part that processes and evaluates the output signal, the method comprising:

• receiving exhaled breath at the gas sensor by way of a scrubber or filter that substantially removes nitrogen monoxide from the exhaled breath so that the exhaled breath at the gas sensor contains no more than a known rest concentration of nitrogen monoxide, the rest concentration being greater than a zero concentration of nitrogen monoxide and being a concentration threshold up to which the measuring device is to produce a zero reading for the concentration of nitrogen monoxide in the exhaled breath;
• processing the exhaled breath in the first part to generate the output signal from the gas sensor, the output signal indicating a measured concentration of nitrogen monoxide in the exhaled breath received at the gas sensor;
• and
• evaluating the output signal with the second part to establish an evaluation value of the concentration of nitrogen monoxide in the exhaled breath and confirming that the evaluation value is zero to verify that the measuring device gives a zero reading when nitrogen monoxide in the exhaled breath at the gas sensor is within a tolerance for generating the zero reading.