ABSTRACT
Most mechanical analog instruments have electronic digital counterparts. All instruments, analog or digital, should be inspected before any test and balance project. A pressure gauge measure pressures above atmospheric and read in pounds per square inch, gauge. Pressure gauges are calibrated to read zero at atmospheric pressure. A sheltered set of instruments is a group of instruments used only to check the calibration of field instruments. In manometers that measure air pressures, the liquid is either water or light oil. U-tube manometers may also be used with a water Pitot tube to take a velocity head traverse of the pipe. A strobe light tachometer has an electronically controlled flashing light which is manually adjusted to equal the frequency of the rotating part; so the part will appear motionless. To avoid reading harmonics of the actual rpm, use nameplate rpm or calculate the approximate rpm and start at that point.
