The influence of different vibration exciter systems on high frequency primary calibration of single-ended accelerometers: II

Abstract

During the monitoring of the long term stability of two accelerometers intended for the use in the CIPM Key Comparison CCAUV.V-K2 significant deviations of the magnitude results of the single ended transducer were discovered. These deviations depend on whether the calibration was performed on an armature made of Beryllium or of ceramic. Further investigations exhibited that this effect must be attributed to some not yet readily understood dynamic process between the contact surfaces of accelerometer and armature. The relative motion underlying the deviations have a significant systematic influence already at 5 kHz and beyond. Therefore, the effect needs to be considered in some way while comparing results within the key comparison, as some laboratories are using Beryllium armatures and some are using ceramic armatures. The contribution describes the details and outcome of the investigations performed on the topic so far and is intended to trigger the necessary discussion of consequences and solutions. 10 kHz 20 kHz Kommentar [Unbekannt1]: Auswert ungScanning.ods (xls von M. Brucke) Erstes Diagramm

Intrinsically accurate sensing with an optomechanical accelerometer

“…As with all primary accelerometer calibrations, [38][39][40][41][42] there are many parasitic dynamic effects that can lead to systematic errors. For instance, we found that it was important to consider non-rigid body motion of the accelerometer package.…”

Absolute calibration device of the vibration sensor

“…The uncertainty of the specified confidence is as follows: According to the previous analysis, the uncertainty of the system can be obtained by taking the horizontal stage as an example, as shown in Table 2. At the same time, it can be known whether the calibration accuracy of the vibration calibration system has been improved; the key factors are as follows: As far as possible, the standard vibration table can minimise the error of the excitation signal, and the single frequency sinusoidal excitation signal can be realised as far as possible, namely, the distortion degree of the system, the uneven surface of the table, and the transverse motion are minimised. The work environment of the laser interferometer is small, and it is properly installed and designed to reduce the measurement error caused by the light path. The effective vibration isolation measures for the system can also reduce the vibration interference of the system and reduce the random uncertainty error of the system. Using more precise and advanced electronic components and instruments to reduce the influence of the system error on the calibration accuracy of the system [8]. …”

A proposal to minimize the dispersion on primary calibration results of single-ended accelerometers at high frequencies

“…Bruns et al have considered in a second publication [6] the inclusion of additional spring and damping elements in the mathematical modeling for a primary calibration of an SE accelerometer, in order to consider finite contact stiffness between the accelerometer and the armature. It was concluded that there are strong evidences that the cause of the problem is a non-negligible relative motion between the SE transducer and the shaker armature at high frequencies.…”

“…This has been reported by Dr. Thomas Bruns in 2009, during the IMEKO TC 22 technical meeting in Lisbon. Later on, two articles related to this problem were published in Metrologia [5] [6].…”