Data Collection & Instrumentation Flashcards

What is the difference between overall vibration level and spectral analysis in a condition monitoring program?

Answer: Overall level provides a single severity value for trending; spectral analysis identifies the frequency and source of vibration components for diagnostics

Overall vibration level (e.g., overall RMS velocity) provides a single trending metric for alarm purposes, while spectral analysis breaks the signal into frequency components that can be linked to specific machine faults for root cause identification.

What is the ISO 20816 standard primarily used for?

Answer: Evaluating machinery vibration severity based on overall RMS velocity measured on non-rotating parts

ISO 20816 (updated from ISO 10816) provides zone-based vibration severity limits in RMS velocity for various machine types, guiding maintenance decisions based on measured vibration on bearing housings and machine supports.

What does 'route-based data collection' mean in a predictive maintenance program?

Answer: A systematic schedule where a technician collects vibration data at predefined measurement points and intervals using a portable analyzer

Route-based collection organizes measurement points into logical geographic routes that a technician follows on a periodic schedule (weekly, monthly) using a portable data collector, enabling consistent trending and anomaly detection.

What is the significance of measurement point location when collecting vibration data on a bearing housing?

Answer: The measurement should be taken as close as possible to the bearing load zone for the most representative signal

Measuring as close as possible to the bearing load zone minimizes the transmission path and attenuation between the fault source and the sensor, ensuring the highest signal-to-noise ratio for defect detection.

What is the purpose of a velocity transducer (seismic pickup) in vibration measurement?

Answer: To measure the absolute velocity of a machine casing using an internal mass-spring system with velocity coil output

A velocity transducer (geophone or seismic pickup) uses an internal mass-spring-damper system and electromagnetic coil to produce an electrical signal proportional to absolute casing velocity, without requiring external power.

Which of the following best describes the function of a tachometer in vibration analysis?

Answer: It provides a once-per-revolution signal used to determine shaft speed and as a phase reference for synchronous measurements

A tachometer (optical, magnetic, or proximity type) generates a pulse once per shaft revolution, providing precise speed information and a phase reference essential for balancing, order tracking, and synchronous averaging.