With this By-pass, exactly 2000 L / min of extra air flows into the milking plant at 50kPa vacuum. This By-pass can be used on both the Electronic and Mechanical Airflow meters. With this By-pass, the capacity of both Airflow meters is increased by 2000 L / min. This means that up to 5000 L / min can be measured. With the use of an additional By-pass (these can be stacked), up to 7000 L / min can be measured.