Accelerometers by nature are sensitive tools. This sensitivity is heavily influenced by how the sensor is mounted. Standard accelerometers are mounted several ways based on need and application. Typical route-based data collecting will be done with a rare earth magnet. The magnet can be either flat or a two-pole type. This provides good data with the ease of moving the magnet around quickly.
Occasionally a guard or other item will inhibit the ability of the analyst to access the best location to collect the readings. In that case you can use a permanent mounted accelerometer or a probe or “stinger” to collect that data.
It’s important to remember when using either of these two options is the probe/stinger can affect the frequency response of the accelerometer. Essentially the added distance the energy must travel through the probe dampens the vibration signal and can impact the frequency response on the upper end of the spectra.
This can be apparent in high frequency data around early stage bearing defects for example. The trade-off for access is accuracy sometimes and some data is better than no data in most cases, so the stinger can be helpful as long as you remember it may/can influence your data.
The chart below illustrates the quality of signal each mounting option can provide. Note the difference from the stinger to a flat magnet.