A method of providing error correction to flow velocity readings of a fluid flowing through a filter arrangement for monitoring the service life of the filter, wherein a filter arrangement, comprising a filter and a sensor device is arranged downstream of the filter, the sensor device including at least one measuring sensor for detecting the flow velocity of the fluid which flows through the filter, and a further measuring sensor for measuring the air humidity of the fluid which flows through the filter. A reading of said second sensor element provides an error correction to the first sensor element.