Although any fluid can be used, mercury is preferred for its high density (13.534 g/cm3) and low vapour pressure. Its convex meniscus is advantageous since this means there will be no pressure errors from wetting the glass, though under exceptionally clean circumstances, the mercury will stick to glass and the barometer may become stuck (the mercury can sustain a negative absolute pressure) even under a strong vacuum. For low pressure differences, light oil or water are commonly used (the latter giving rise to units of measurement such as inches water gauge and millimetres H2O). Liquid-column pressure gauges have a highly linear calibration. They have poor dynamic response because the fluid in the column may react slowly to a pressure change.
Although any fluid can be used, mercury is preferred for its high density (13.534 g/cm3) and low vapour pres.sure. Its convex meniscus is advantageous since this means there will be no pressure errors from wetting the glass, though under exceptionally clean circums.tances, the mercu.ry will stick to glass and the barometer may become stuck (the mercury can sustain a negative absolute pressure) even under a strong vacuum. For low pressure differences, light o:il or water are commonly used (the latter giving rise to units of measurement such as inches water gauge and millimetres H2O). Liquid-column pressure gauges ha.ve a highly linear calibration. They have poor dynamic response because the fluid in the column may react slowly to a pressure change.