Quality Of The Surface The Sensor - CEMB TR-NC/8 Manual Del Usuario

4.8 Quality of the surface the sensor faces
The roughness of the surface the sensor faces affects the measurement sensitivity.
• For this reason, roughness values between 0.4 and 0.8 μm RMS (API directives) are required.
• Surfaces should not be faced with galvanic coatings.
4.9 Runout
RUNOUT means the summation of the errors relating to the area of the shaft the sensors are facing, which falsify the
measurement result.
• Mechanical RUNOUT:
Caused by deviation of the shaft area the sensor is facing from the ideal circular shape and by elliptic rotors.
This runout can be measured using mechanical devices, such as dial gauges or a no-contact transmitter.
The measurement is to be made with a number of revolutions between 1 and 100 where vibration phenomena
do not occur.
• Electrical RUNOUT:
Caused by the effect the structure of the shaft material has on the signal measured by the demodulator.
A variation in the measured value is caused by the following phenomena:
> Non-uniform shaft density.
> Inhomogeneous conductivity caused by alloy material distribution.
> Residual magnetism.
The RUNOUT is constant in phase and amplitude as the number of revolutions vary and might be added to or sub-
tracted from the actual vibration, falsifying the measurement made.
Measured
vibration
Actual
vibration
RUNOUT
RUNOUT in phase with vibration
RUNOUT and vibration shifted 180° out
RUNOUT
Measured
vibration
Actual vibration
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