AiVibeSampling Rate and the Nyquist Criterion
The sampling rate is the number of samples per second taken from a signal during digitisation; the Nyquist criterion states that it must exceed twice the highest frequency present to represent the signal without aliasing.
When a continuous signal is sampled, frequency components above half the sampling rate, the Nyquist frequency, fold back and appear as false lower frequencies, an effect called aliasing that cannot be removed after sampling. Data acquisition systems therefore place an analogue anti-aliasing low-pass filter before the converter to attenuate content above the Nyquist frequency. In practice, sampling rates are chosen comfortably above twice the highest frequency of interest, because real filters do not cut off sharply.
Required rates differ widely by signal. Temperatures and tank levels change slowly and need only occasional samples, while vibration analysis of bearings and gears, power quality measurement and acoustic monitoring need rates in the kilohertz range or higher. Sampling too slowly loses information or creates misleading aliases; sampling too fast wastes bandwidth, storage and processing.
Sampling rate should be distinguished from the reporting or logging rate in IIoT systems: a sensor may sample at high speed internally and report only summary features such as RMS values or peaks. Simultaneous sampling matters when phase relationships between channels are analysed. Timestamps, clock accuracy and jitter affect the usefulness of sampled data for correlation and frequency analysis.
Key points
- Number of samples taken per second during digitisation
- Must exceed twice the highest frequency present to avoid aliasing
- Anti-aliasing filters attenuate content above the Nyquist frequency
- Vibration and power quality need far higher rates than temperature
- Internal sampling rate can differ from the reporting rate
Where AiVibe comes in
AiAmbA IoT is AiVibe's edge protocol layer: it discovers devices and normalises industrial signals, with supported protocols including Siemens S7, Mitsubishi MC, Delta Modbus, OPC UA and MQTT, and driver availability confirmed per installation. Writes to machines are deny-by-default.
Related terms
- Data Acquisition (DAQ)Industrial IoT & Edge
- Analogue-to-Digital Converter (ADC)Industrial IoT & Edge
- Signal ConditioningIndustrial IoT & Edge
- Vibration Sensor (Accelerometer)Industrial IoT & Edge
- Report by Exception (RBE)Industrial IoT & Edge