What Is Settling Time?

Settling time can be described as the amount of time you must wait to make a vibration measurement after: 

• Turning the power on 
• Connecting the sensor 
• “Mounting” the sensor (connecting the magnet-mounted sensor to the machine) 

There are four primary components that must all be “at the ready” prior to taking the data collector readings. 

1. Mounting
   The sensor must be properly mounted and not “in motion” prior to powering the sensor.
   
   
2. Sensor
   Once the sensor is mounted, it must have time to allow the internal mechanics to stop any excessive motion caused by the mounting or repositioning of the sensor.
   
   
3. IEPE Power
   Whether supplied by the data collector or by an independent power supply, this is the main thing that must be working properly. Even small fluctuations in current/voltage supply can affect the output from the sensor.
   
   
4. Measurement System
   This is your analyzer or other data acquisition system. Even though these generally settle within a few milliseconds it is still possible for the eager analyst to punch their record button twice in rapid succession before the data collector is ready to take a second reading.

What problems can occur if the system has not settled? 

1. Ski Slope
   A large DC voltage component swamps the low-frequency region of the spectrum causing a “ski slope." To correct this the analyst needs to wait for all components of the system to settle before taking a measurement. Most sensors settle from powering on in under two seconds. 
   
   
2. Unwarranted Spikes in the Spectrum
   These can be caused by slamming the sensor and magnet onto the machine and attempting to take a reading before the system has settled. If a sensor has been slammed onto the machine it usually requires a settling time in the neighborhood of four seconds for the sensor to settle and for the power supply to de-couple and settle. This can be avoided by gently rocking the magnet onto the machine.