Test and comparison of LVDT signal conditioner performance

Abstract

This paper presents the results of a novel digital signal processor (DSP) based technique for signal conditioning of Linear Variable Dgferential Transformers (L VDTs).Signal conditioning is achieved through a modified DSP-based Costas receiver. This system is tested and compared with two commercially available analog signal conditioners and a second DSP-based signal conditioner. The system developed by the authors has better dynamic response than existing solutions and better noise rejection than commercially available solutions. Static testing of the system using both 4-wire and 5-wire LVDTs verifies that the conditioner meets or exceeds the linearity performance of existing signal conditioning systems over the full-scale operating range. In addition, this system requires no phase compensation network or manual tuning.

LVDT Conditioning on the LHC Collimators

“…This ensures a compensation of the amplitude drift on the excitation signal. The noise immunity of this solution is not better than that obtained with a synchronous demodulation especially if it is used in a 4-wire configuration [7]. Ratiometric conditioning however implies that the sum of the two secondaries has to be independent of the position of the LVDT core to not affect the measurement linearity.…”

Automatic test bench for the measurement of the magnetic interference on LVDTs

“…In fact, several methods exist to evaluate the position on the basis of the amplitude of the secondary coils, which are basically amplitude demodulation procedures [7]. The reading technique also depends on LVDT type and, more specifically, on the available wires of the coils.…”

“…A five-wire model makes available the central point of the series of the secondary coils, whereas a six-wire model provides all the output legs of the coils. Different techniques have been proposed and investigated [3], [7]- [10]. The three main techniques are differential reading (V sec1 − V sec2 ), normalized differential reading (V sec1 − V sec2 )/V pri , and ratiometric reading The digital technique based on ratiometric function, which links the core position to the ratio between the difference and the sum of the output voltages of the secondary coils, is mostly used for a five-or a six-wire model since it assures high performance, and the reading position is independent of the primary coil variation [7].…”

“…According to its design and its available wires, a differential or a ratiometric reading [3], [7]- [10] is used, and the nonlinearity and uncertainty of the sensor are given. Then, the procedure is detailed to analyze the sensor under test in the presence of an external magnetic field on the LVDT.…”

Design of a Linear Variable Differential Transformer With High Rejection to External Interfering Magnetic Field

“…The resolution and the accuracy of such a sensor are mainly determined by the conditioning electronics and the correction algorithm used [3]. Digital conditioning approaches [4], [5], together with a ratiometric reading technique [1], ensure high linearity and reading accuracy, even in conditions of low signal-tonoise ratio.…”