A pH meter measures the acidity or alkalinity of a fluid, providing critical information about its chemical properties. The quality of a fluid can be inferred from its pH level; for instance, if a substance expected to be acidic tests alkaline, it indicates poor quality. This discrepancy can signal contamination or degradation of the fluid. Understanding pH is essential for assessing the suitability of various fluids for specific applications. Ultimately, the definition of "quality" in this context hinges on the expected pH characteristics of the fluid being tested.