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New calibration device for dynamic calibration of bridge amplifiers

16.10.2018

The dynamic calibration of bridge amplifiers is an important prerequisite for the dynamic characterisation of force, pressure and torque transducers. A new calibration device based on a dynamic bridge standard developed at PTB enables these dynamic calibrations up to a frequency range of 10 kHz.

The calibration device of working group 1.73 Impact Dynamics uses a dynamic bridge standard developed and calibrated at PTB in working group 2.12 Ratio and Sampling Techniques [1]. The bridge standard simulates the bridge detuning by a corresponding transducer by generating a corresponding dynamic bridge voltage. This voltage depends on the supply voltage of the amplifier.

For calibration, the reference signal of the bridge standard and the output signal of the amplifier under test are acquired simultaneously. This is carried out using an accurate signal acquisition card. The dynamic properties of the acquisition card have also been determined beforehand.

The dynamic bridge standard has been dynamically calibrated in working group 2.12 prior to the measurements. Thus, the properties of the reference output signal and the output signal for the bridge amplifier are known.

Based on the acquired signals, the magnitude response of the examined bridge amplifier can be determined from the output signal of the amplifier alone; the reference signal is also used to determine the phase response. The transfer function is determined by means of a discrete Fourier transform.

First promising measurements have already been carried out [2]. The measurement uncertainty components are currently being estimated [3]. After extensive test measurements, the measurement uncertainty for the calibration set-up will then be determined.

 

 

Figure 1: Calibration device with a typical bridge amplifier as used for dynamic measurements (top), the dynamic bridge standard (middle) and the measurement data acquisition electronics (bottom).

Literature:

[1] M.F. Beug, H. Moser, G. Ramm: Dynamic Bridge Standard for Strain Gauge Bridge Amplifier Calibration, Proc. of CPEM, Seite 568-569, Washington, D.C., U.S.A., DOI: Opens external link in new window10.1109/CPEM.2012.6251056

[2] L. Klaus, F. Beug and Th. Bruns: A new calibration set-up for the dynamic calibration of bridge amplifiers from DC up to 10 kHz, Proc. of IMEKO TC3, TC5 and TC22 International Conference 2017, Helsinki, Finnland: Opens external link in new windowhttp://www.imeko.org/publications/tc3-2017/IMEKO-TC3-2017-011.pdf

[3] L. Klaus, F. Beug and Th. Bruns: Calibration set-up for the dynamic calibration of bridge amplifiers from DC up to 10 kHz, Acta IMEKO, 2018, in press.

Contact:

Dr.-Ing. Leonard Klaus, FB 1.7, AG 1.73, e-mail: Opens window for sending emailleonard.klaus(at)ptb.de