Which of the following is NOT a minimum requirement of a hydraulic system?

A hydraulic system primarily consists of several key components that are essential for its operation. These include a source of power, which is necessary to generate the hydraulic pressure that powers the system. This can come from a hydraulic pump driven by an engine or motor. Additionally, there must be a means to transmit that power, typically through hydraulic fluid flowing through hoses and pipes to various components of the system. Furthermore, there are devices designed to utilize that power effectively, such as hydraulic cylinders or motors that perform work.

The component listed regarding the measurement of temperature is not a minimum requirement for a hydraulic system. While monitoring temperature can be important for operational safety and efficiency, it is not essential for the basic function of a hydraulic system. Therefore, not having a device to measure temperature does not impede the fundamental operation of hydraulic systems, making it the correct answer for identifying what is NOT a minimum requirement.