Very low frequency IEPE accelerometer calibration and application to a wind energy structure

Abstract

Abstract. In this work, we present an experimental setup for very low frequency calibration measurements of low-noise integrated electronics piezoelectric (IEPE) accelerometers and a customised signal conditioner design for using IEPE sensors down to 0.05 Hz. AC-response IEPE accelerometers and signal conditioners have amplitude and phase deviations at low frequencies. As the standard calibration procedure in the low-frequency range is technically challenging, IEPE accelerometers with standard signal conditioners are usually used in frequency ranges above 1 Hz. Vibrations on structures with low eigenfrequencies like wind turbines are thus often monitored using DC-coupled micro-electro-mechanical system (MEMS) capacitive accelerometers. This sensor type suffers from higher noise levels compared to IEPE sensors. To apply IEPE sensors instead of MEMS sensors, in this work the calibration of the entire measurement chain of three different IEPE sensors with the customised signal conditioner is performed with a low-frequency centrifuge. The IEPE sensors are modelled using infinite impulse response (IIR) filters to apply the calibration to time-domain measurement data of a wind turbine support structure. This procedure enables an amplitude and phase-accurate vibration analysis with IEPE sensors in the low-frequency range down to 0.05 Hz.

Identification Uncertainties of Bending Modes of an Onshore Wind Turbine for Vibration‐Based Monitoring

“…An additional sensor of tangential direction is attached to one measuring point (MP1t) per measuring level, as shown in Figure 2. Te calibrated IEPE sensors are combined with an IEPE supply with a cutof frequency of 0.0106 Hz, enabling the measurement of acceleration signals without distortion down to 0.05 Hz [17]. Te measurement data of all sensors are digitised synchronously with a 24 bit analogue to digital converter on Level 1 positioned and stored on a computer with a sampling rate of 500 Hz.…”

“…Te low-frequency system dynamics are also challenging to capture. Terefore, the measurement chain must be designed and calibrated for the low-frequency range [17]. All these efects ultimately increase the identifcation uncertainty of the modal parameters [18].…”

Experimental Investigation on the Transfer Behavior and Environmental Influences of Low-Noise Integrated Electronic Piezoelectric Acceleration Sensors

“…The MOSFET enables high-impedance voltage signals to be amplified to low-impedance voltage signals. This leads to significantly better noise performance and less loss of signal quality [24]. Due to this low-loss signal transmission, inexpensive coaxial cables, which may be several hundred meters long, can be used without concerns about losing the quality of the measurement signal, such as increased noise or susceptibility to environmental factors [41].…”

“…In addition to long stroke distances, there are alternative calibration methods. For example, Olivares et al in [23] and Jonscher et al in [24] utilized an inclined centrifuge to calibrate acceleration sensors, relying on the earth's gravitational field and the centrifuge's inclination rather than stroke distance.…”

Dynamic displacement measurement of a wind turbine tower using accelerometers: tilt error compensation and validation

“…According to Stiros (2008), the measurement time, sampling rate and noise level of the measurement technology have the greatest influence when estimating displacement from acceleration measurement data. In the context of wind turbine towers, there are further recent studies (Jonscher et al, 2022b;Botz, 2022;Jonscher et al, 2022a) that investigate methods to obtain displacements from acceleration measurements. Jonscher et al (2022b) showed that estimated dynamic displacements with calibrated Integrated Electronics Piezo Electric (IEPE) accelerometers and Micro-Electro-Mechanical-Systems (MEMS) accelerometers in the frequency range down to 0.05 Hz yield similar results.…”