Triax transducers have three sensors within a single housing measuring all three vibration axes (X, Y and Z). There is an argument in favor of mounting a triax sensor in the middle of a motor, asserting that it can provide all of the necessary data for defect analysis. Triax sensors are also beneficial when collecting large amounts of either Modal or Operational Deflection Shape (ODS) data. A special impact hammer can be used to measure all three axes of vibration data for Modal analysis, minimizing the number of impacts and effort required to collect this type of data.
However, certain disadvantages are associated with triax sensors that also should be taken into consideration. For example, some defects can be missed until very late in the failure mode when the sensor is used at a single sensor location. This can reduce the amount of time available to take corrective action on the equipment being monitored. Triax sensors can be quite expensive when compared to standard vibration sensors. Additionally, the data collector being used must have the electronic capabilities to utilize these types of sensors.
Vibration Analysis by Gary James CRL