### ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

## 5pSA10. Electrodynamic reciprocity method for vibration standards.

**Li-Feng Ge
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*Anhui Bureau of Tech. Supervision, 30-Ma An Shan Rd., Hefei, Anhui 230001,
People's Republic of China
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In a previous paper, a reciprocity calibration formula different from the
Levy--Bouche's is derived [L.-F. Ge, Proceedings of the XIII IMEKO World
Congress, 2606--2610 (1994)]; the latter has been regarded as a standard method
[ISO 5347-0, 1987; ISO/DIS 5347-20, 1990]. The new formula is
S=(RT/j(omega))[sup 1/2] (V/ms[sup -2]), where T is the mean of the transfer
admittance ratio, T[sub n]=M[sub n]/(Y[sub n]-Y[sub o]) and R is the voltage
ratio for the typical three-transducer-two-experiment procedure, in which an
electrodynamic transducer serves as reciprocal one. This method is suited to
the low- and mid-frequency ranges, and most accurate at 100--1000 Hz. This
paper reveals that a coefficient of variation, i.e., ratio of standard
deviation of T[sub n] to its mean value, can be viewed as a reciprocity index
of such an electrodynamic calibration system including two transducers and a
solid mass medium. An index smaller than 0.5% indicates that the system is
better reciprocal, and can be calibrated more accurately. At frequencies higher
than about 3000 Hz, nonlinear problems, such as stress wave effect and
resonance, become pronounced, and should be considered; a better way would be
to apply other more available methods, such as the laser interferometry and
piezoelectric reciprocity method.