The Isoprobe should be installed at end of tubing. We have barbed Isoprobes that can attach to the end of the tubing. Make sure the tubing is a short as possible (no longer than 10 feet, or it could damage the pump).
The Isokinetic probe is designed to allow the airflow coming onto the instrument to maintain Isokinetic flow throughout the optical block. We do not want the airflow to be interrupted as it enters the sensor – this could skew the particles within the air stream and provide inaccurate counts.