Key component of any acoustic fluid level instrument such as the okemos™ is a pressure pulse generator.
The Leutert pressure pulse gun consists of a volume chamber that may be isolated from the well by a quick opening plunger valve once the gas gun is connected to the casing or tubing flow line. The volume chamber is then either charged with CO2 or nitrogen at a pressure greater than the pressure in the wellbore. When the level gun is triggered the plunger valve will rapidly open. Due to the pressure differential between volume chamber and wellbore a positive pressure pulse is generated. It travels down the well and echoes from the fluid level (explosion). A dual disc pressure sensitive microphone incorporated into the gas gun will sense this echo and converts it into a 4 to 20 mA output signal.
Alternatively gas from the wellbore may be quickly vented into the volume chamber (implosion) causing a negative pressure pulse traveling down the well and back. An external gas source is not needed but a wellhead pressure of at least 50 to 100 psi is required.