What should the highest end of the pressure gauge scale represent?

The highest end of the pressure gauge scale should represent a value that is not greater than five times the test pressure. This is established to ensure the gauge can accurately measure a range of pressures without risk of damage or reduced accuracy at extreme pressures.

Using a scale that exceeds five times the test pressure could lead to complications such as inaccurate readings, as gauges are typically calibrated to work best within a certain range. Having a scale that is much higher than necessary can also make it difficult to accurately read lower pressures, which are often the values of interest during regular operations or testing scenarios.

The other options suggest using scales that could exceed this recommended limit or fall below it, which would not provide the necessary accuracy or safety in pressure measurement. Hence, adhering to the five times the test pressure guideline aligns with best practices in pressure gauge selection and use.