To determine why a venturi tube is not operating properly, the technician should check with which of the following?

The correct approach to determine why a venturi tube is not functioning properly revolves around checking the minimum required psi (pounds per square inch) and cfm (cubic feet per minute) at the input. This is crucial because the operation of a venturi tube relies significantly on the pressure and flow rate of the gas or fluid passing through it.

A venturi tube operates on the principle of fluid dynamics, where the pressure decreases as the fluid flows through a constricted section of the tube, leading to a velocity increase. If the input does not meet the minimum psi and cfm specifications, the necessary pressure differential needed for the venturi effect will not be established. This can result in inadequate flow, inconsistent performance, or complete failure of the venturi tube to function correctly.

Verifying that the pressure and flow rate meet the manufacturer's specifications ensures that the venturi tube can create the required conditions for its operation, thereby allowing for proper diagnosis and troubleshooting of any issues.