Data Collection & Instrumentation Flashcards

What is 'order tracking' in vibration analysis of variable-speed machinery?

Answer: A resampling technique that converts time-domain data to shaft-angle domain, keeping vibration components synchronized with shaft speed

Order tracking synchronizes data acquisition to shaft rotation (using a tachometer), so that shaft-synchronous components remain at fixed orders regardless of speed changes, enabling clean spectral analysis of variable-speed machines.

What is the purpose of a charge amplifier used with piezoelectric sensors?

Answer: To convert the high-impedance charge output of charge-mode piezoelectric sensors to a low-impedance voltage suitable for recording and analysis

A charge amplifier converts the very high impedance charge (picocoulombs) from charge-mode piezoelectric sensors to a low-impedance voltage output, enabling connection to standard recording equipment with acceptable noise levels.

What is meant by the 'sensitivity' of an accelerometer, and what are its typical units?

Answer: The ratio of electrical output to mechanical input (acceleration); typical units are mV/g or pC/g

Accelerometer sensitivity specifies the electrical output produced per unit of acceleration input (e.g., 100 mV/g for ICP sensors or 10 pC/g for charge-mode sensors) and must be entered into the analyzer to obtain calibrated amplitude readings.

What is the purpose of a vibration data collector's 'alarm' and 'alert' levels in a route-based program?

Answer: Alert is a warning threshold prompting closer monitoring; alarm indicates a more serious condition requiring prompt maintenance action

In most condition monitoring programs, alert (or warning) is a lower threshold indicating a developing issue requiring increased monitoring frequency, while alarm (or danger) is a higher threshold indicating the need for prompt maintenance action.

What is the function of a signal conditioner in a vibration measurement system?

Answer: To provide sensor power, amplification, filtering, and signal conversion between the transducer and the data acquisition system

A signal conditioner provides the constant current excitation for ICP sensors, amplifies the low-level signal to the ADC input range, applies anti-aliasing filtering, and may perform integration from acceleration to velocity or displacement.

What is the API 670 standard, and what type of machinery protection does it address?

Answer: The American Petroleum Institute standard for machinery protection systems, specifying online vibration monitoring requirements for critical rotating equipment

API 670 defines requirements for continuous online machinery protection systems (proximity probe systems, vibration monitors, speed detectors) for critical rotating equipment in oil and gas plants, including alarm and shutdown logic.