High frequency accelerometers
High frequency accelerometers are used on machinery with gear mesh or small bearings, such as high speed machine tool spindles and compressors.
High frequency sensors are available with 100 mV/g or 10 mV/g output sensitivity.
The 10 mV/g version is most commonly used due to its high amplitude range which can prevent sensor overload. Actually there is little vibration in terms of displacement and velocity at high frequency; however tremendous amounts of acceleration amplitudes may be present. It is not uncommon for vibration amplitudes on a very high speed gearbox to exceed 80 g peak prior to failure: high frequency accelerometers with low voltage sensitivity will prevent sensor overload from these high amplitudes. Whereas a 100 mV/g accelerometer may overload at 50g peak, a 10 mV/g senso will measure to 500g peak.
Since high frequency sensors are generally smaller and lighter weight than their general purpose or low frequency counterparts, they have the advantage of less mass loading: mounting of the sensor will have less tendency to change the vibration of the structure under test.
However, the signal to noise ratio will be reduced with high frequency units because of the lower sensor sensitivity. If measurement of low-level signal is necessary, check the narrowband noise levels of the sensor.
|Model||Sensitivity||Sensitivity tolerance +/-||Frequency response @ +/- 3db||Max temp.||Accel Range||Haz area option|
|High frequency accelerometers|
|712F||100 mV/g||10%||3.0 - 25k||120°||60|
|732A-732AT||10 mV/g||5%||0.5 - 25k||120°||500|
|736-736T||100 mV/g||5%||2.0 - 25k||120°||50|
|997||10 mV/g||10%||0.5 - 29k||120°||600|