Which system uses a pressure regulator to maintain constant pressure during spraying?

The correct answer involves understanding how pressure regulation is critical in various types of sprayers to achieve uniform application of pesticides. In particular, backpack sprayers are designed to be portable and often use a simple manual pump to create the required pressure for spraying. However, they may not have a sophisticated pressure regulation system in place, which can lead to variations in pressure during operation.

On the other hand, hydraulic sprayers are specifically engineered with a pressure regulator that maintains a constant pressure during operation. This feature is essential because it ensures that the pesticide is delivered at a consistent rate and droplet size, which is crucial for effective pest control and minimizing drift.

Vehicle-mounted sprayers and selectable sprayers also benefit from pressure regulation, but they are often not referred to in the context of backpack sprayers. For vehicle-mounted sprayers, the systems are larger and more complex, typically utilizing advanced technology to regulate pressure, while selectable sprayers may offer various modes of operation but still rely on consistent pressure for optimum performance.

Thus, the references to pressure regulation make hydraulic sprayers the most accurate choice when discussing systems specifically designed for maintaining constant pressure during spraying operations.