Result

Three values are displayed. The Velocity and BDU values are color coded to show their alarm status.

  • Velocity. RMS or Peak (shown in mm/second or inch/s)
  • Bearing Noise in BDU (Bearing Damage Units)
  • Total g (acceleration)

Go to Vibration analysis.

RMS value

The ISO value (in mm/s or inch/s) is the RMS (average) of the vibration velocity in the frequency band 10Hz (600 RPM) to 1kHz (60,000 RPM) or 2Hz (120 RPM) to 1kHz (60,000 RPM), as specified by the ISO standard. The correct frequency band is automatically selected by the XT280 based on running speed. The background is color coded according to the ISO 10816-1 vibration velocity level chart (see below). The color coded background indicates the condition of the machine according to the size and type of machine selected. Go to Configuration.

ISO 10816-1:1995. Mechanical vibration - Evaluation of machine vibration by measurements on non-rotating parts.

Bearing Noise (BDU)

Bearing noise (high frequency vibration) in Bearing Damage Units (BDU), where 100 BDU corresponds to 1g RMS (average) vibration measured above 1kHz. This is a measure of the wear state of the bearings in the equipment being monitored. The higher the number, the more worn the bearing.

It is commonly held that 1g of high frequency vibration (100 BDU) corresponds to a relatively high level of bearing noise and so can be considered indicative of a damaged bearing. In other words, it may be helpful to think of the Bearing Noise figure as being very roughly equivalent to “percentage” of bearing wear.

By default, the bearing noise is displayed on a

  • Red background if it is above 100 BDU
  • Amber background between 50 and 100 BDU
  • Green background below 50 BDU.

The BDU alarm levels can be changed. Go to Configuration.

Total acceleration (g)

This is the RMS (average) value of the total vibration acceleration measured by the meter over its entire frequency range (2Hz to 10kHz). This reading is shown in units of g (Earth’s gravitational constant, where 1g = 9.81 m/s2).

RMS displacement

Press the left (<) or right (>) arrow button when the reading screen is displayed will display RMS displacement (in µm or mils) on a blue background. Press either arrow button again will revert to display of the ISO value (mm/s or inch/s).