Mid Sweden University

This paper proposes a torque measurement method based on volumetric strain. A model of the measurement system based on the differential pressure monitoring is proposed and theoretically discussed. The error sources are identified and an error propagation model is presented for the proposed torque measurement method. Considering these error sources, a prototype torque sensor is presented as a case study for the method verification. Both the mechanical and readout electronics design are discussed and analyzed. The mechanical sensitivity and maximum stresses are analyzed using Finite Element Method. Whereas, the readout electronics is experimentally verified using an off-the-shelf high performance differential pressure sensor. The results from the conducted analysis show that the presented design of torque sensor can be used to measure torque in the range of ±300 N·m with the resolution of 0.006 % of full scale. The maximum observed stress on the proposed structure is 220 MPa. The experiments conducted on the readout electronics show that the differential pressure sensor is the limiting factor in the design when it comes to the resolution. In conclusion it is summarized that the presented torque sensor can be used in industrial applications requiring both high resolution and wide range. Moreover, the method is fully adaptable to various performance requirements in terms of range and resolution. The future work is also discussed to implement the presented design and characterize it using reference instruments.

The calibration of sensors is one of the most frequently carried out maintenance operations on sensor networks. This paper presents the design of a reference instrument for the static calibration of low-range (up to ±320 Pa) differential pressure sensors. A method is proposed for the calibration setup and the design issues are discussed in addition to a complete error analysis. An experimental setup is also proposed. From the conducted experiments, it is verified that the sensitivity of the reference setup is at least 0.032 Pa with the achievable resolution of 0.001% of full scale. This paper also presents an embedded electronics design for both the calibration and the characterization profile handling. A full performance characterization of a sample differential pressure sensor is also presented in terms of sensitivity, linearity, hysteresis, and temperature dependency. A comprehensive discussion involving the design parameters analysis and the worst case performance is also included. In conclusion, it is summarized that the proposed design out performs the conventional reference instruments, so that it can be used for the calibration and characterization of a wide variety of low-range differential pressure sensors.

Low range differential air pressure sensors are used widely in various applications. In this paper the effects of temperature change on transient behavior of the calibration setup for differential air pressure sensors, due to temperature gradient are analyzed. A high performance reference setup utilizing ideal gas law, for differential air pressure sensors, is selected for experimental analysis. The range of the setup is ±320 Pa with the achievable resolution down to 0.001% of the full scale. Due to the nature of ideal gas law, the experimental setup should also exhibit a high sensitivity to the temperature gradient on mechanical structure. In order to characterize the effects of this temperature gradient on the transient state of the setup, a two stage comparative experimental study is proposed. In stage one a thermal buffer is introduced surrounding the mechanical structure of the setup and the experiments are conducted by changing the temperature to the system. In stage two the temperature is changed in the same manner, but the experiments are conducted with the original experimental setup. From the results obtained by the experiments using the thermal buffer, it is observed that the temperature change of 5°C, can cause the system to stay in transient state for up to 32 hours with an error of up to 10% of full scale. Whereas, the results from the original calibration setup show that the system stays in transient state for more than 96 hours with a monotonic drift. From the comparative analysis of the experimental results we conclude that the high sensitivity calibration setup for differential air pressure sensors also have a high sensitivity to the temperature gradient. Although the thermal buffer can minimize the effects of the temperature gradient on the transient behavior of the calibration setup, the modification to the existing mechanical design is considered as more practical. Future work is proposed in order to study the thermal gradient on the mechanical structure and design a setup that is less vulnerable to it. © 2015 IEEE.

This paper focuses on the thermal stability of a high performance, low-range calibration setup for differential airpressure sensors. The setup is a dual parallel chamber design with the full range of ±320 Pa, which can be translated to a temperature mismatch of only about 0.93oC between the chambers. Due to the limitations of existing temperature measurement technology, we propose a finite element model(FEM) analysis to study the effect of thermal gradient on the calibration setup. The model setup includes the dual parallel chamber design inside a conventional climate chamber. From the conducted analysis we observe that, due to the non-ideal heat distribution inside the climate chamber, the calibration setup can experience an error of more than 20 % of full range.To minimize this error, we propose an optimized dual cascaded chamber calibration setup design and verify its thermal performance under the same environmental setup. The results show that the proposed design reduces the error, due to thermal gradient, down to 1.8 % of full range. In conclusion it is also discussed that the proposed design reduces error sources related to its mechanical complexity. Future work is proposed on the design and implementation of the optimized design.

This paper presents an experimental comparative analysis of a torque measurement method based on volumetric strain, utilizing a prototype torque sensor design is compared to a reference high performance torque sensor. A brief description of the background work of the numerical analysis of the method is also discussed as well as the readout electronics design. Based on the simulations and readout electronics analysis it is concluded that the sensor has a mechanical range of ±300 N·m. The manufacturing details of the prototype torque sensor are also discussed. A test setup is used to place the two torque sensors in line, to allow comparison for which a high performance conventional off-the-shelf torque sensor is selected. The experiments show that the proposed method of torque measurement can be fully implemented and used to measure torque with higher response time, resolution and wider range. Furthermore, future work is proposed to fully characterize the sensor over the full range using a reference setup rather than a torque sensor, as the available conventional sensors cannot be used to characterize the prototype torque sensor in full range with higher performance than the sensor itself.