10-12-2012, 02:01 PM
The Art of Instrumentation & Vibration Analysis
The_Art_of_instrumentation.ppt (Size: 3.28 MB / Downloads: 174)
Displacement Sensors
How it Works:
The tip of the probe contains an encapsulated wire coil which radiates the driver's high frequency as a magnetic field. When a conductive surface comes into close proximity to the probe tip, eddy currents are generated on the target surface decreasing the magnetic field strength, leading to a decrease in the driver's DC output. This DC output is usually 200mV/mil or in a similar range.
Velocity Sensors
Pro’s and Con’s
Pro’s
Measures Velocity
Easier Installation than Displacement
Con’s
Limited Frequency Range (0-1000Hz)
Susceptible to Calibration Problems
Large Size
Acceleration Sensors
Pro’s and Con’s
Pro’s
Measures Accel.
Small Size
Easily Installed
Large Frequency Range (1-10,000 Hz)
Con’s
Measures Acceleration (requires Integration to Vel.)
Susceptible to Shock & Requires Power
AC and DC Signal Components
Signals have both AC and DC
AC considered the “Dynamic” Signal
DC is the “Static” Signal
Displacement Probes – Set “Gap” for DC
Accelerometers – “Bias” voltage is DC