Measurement and control of the movable coil position of a joule balance with a system based on a laser heterodyne interferometer

Yang, Hongxing; Lu, Yunfeng; Hu, Pengcheng; Li, Zhengkun; Zeng, Tao; He, Qing; Zhang, Zhonghua; Tan, Jiubin

doi:10.1088/0957-0233/25/6/064003

Cited by 25 publications

(18 citation statements)

References 7 publications

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“…The laser interferometer was also utilized to measure the relative displacement between the two coils and verify the performance of the differential capacitor sensor. In order to maintain a fixed relative position of the two coils along z-axis, a piezoelectric ceramic (PZT) and feedback control system are utilized to compensate the vibration and drift of relative displacement between the two coils [ 20 ]. The experiment result is shown in Figure 8 .…”

Section: Experimental Setup and Resultsmentioning

confidence: 99%

Absolute Position Sensing Based on a Robust Differential Capacitive Sensor with a Grounded Shield Window

Bai

et al. 2016

Sensors

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A simple differential capacitive sensor is provided in this paper to measure the absolute positions of length measuring systems. By utilizing a shield window inside the differential capacitor, the measurement range and linearity range of the sensor can reach several millimeters. What is more interesting is that this differential capacitive sensor is only sensitive to one translational degree of freedom (DOF) movement, and immune to the vibration along the other two translational DOFs. In the experiment, we used a novel circuit based on an AC capacitance bridge to directly measure the differential capacitance value. The experimental result shows that this differential capacitive sensor has a sensitivity of 2 × 10−4 pF/μm with 0.08 μm resolution. The measurement range of this differential capacitive sensor is 6 mm, and the linearity error are less than 0.01% over the whole absolute position measurement range.

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Section: Experimental Setup and Resultsmentioning

confidence: 99%

Absolute Position Sensing Based on a Robust Differential Capacitive Sensor with a Grounded Shield Window

Bai

et al. 2016

Sensors

Self Cite

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“…The positions z 1 and z 2 are two static positions of the suspended coil. Especially, when the laser based position locking technique proposed in [6] is used, the position z 1 and z 2 can be very stable. Therefore, the value of ψ(z 2 ) -ψ(z 1 ) is a fixed value when the current in the whole second coil remains constant.…”

Section: Adopting the Magnetic Flux Linkage Directlymentioning

confidence: 99%

Coils and the Electromagnet Used in the Joule Balance at the NIM

Zhang

Han

et al. 2015

IEEE Trans. Instrum. Meas.

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Abstract-In the joule balance developed at National Institute of Metrology (NIM), the dynamic phase of a watt balance is replaced by the mutual inductance measurement in an attempt to provide an alternative method for the kg redefinition. But for this method a rather large current in the exciting coil, is needed to offer the necessary magnetic field in the force weighing phase, and the coil heating becomes an important uncertainty source. To reduce coil heating, a new coil system, in which a ferromagnetic material is used to increase the magnetic field was designed recently. But adopting the ferromagnetic material brings the difficulty from the nonlinear characteristic of material. This problem can be removed by measuring the magnetic flux linkage difference of the suspended coil at two vertical positions directly to replace the mutual inductance parameter. Some systematic effects of this magnet are discussed.

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“…A laser heterodyne interferometer is incorporated into a three-axis simultaneous differential interferometer to measure the relative displacement between the suspended coil and the exciting coil [12], as shown in Fig. 4.…”

Section: Laser-based Position Locking System Of the Suspended Coilmentioning

confidence: 99%

“…5 shows the vibration and drifting of the suspended coil. To keep the suspended coil stable, three oil damping devices are used to decrease the swing along the balance beam and the conical swing [12]. An active control technique to decrease the vibration and drift of the suspended coil is also proposed by authors and has been verified with a model [12].…”

Section: Laser-based Position Locking System Of the Suspended Coilmentioning

confidence: 99%

The Improvement of Joule Balance NIM-1 and the Design of New Joule Balance NIM-2

Zhang

et al. 2015

IEEE Trans. Instrum. Meas.

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The development of the joule balance method to measure the Planck constant, in support of the redefinition of the kilogram, has been going on at the National Institute of Metrology of China (NIM) since 2007. The first prototype has been built to check the feasibility of the principle. In 2011, the relative uncertainty of the Planck constant measurement at NIM is 7.7 × 10 −5 . Self-heating and swing of the coils are the main uncertainty contributions. Since 2012, some improvements have been made to reduce these uncertainties. The relative uncertainty of the joule balance is reduced to 7.2 × 10 −6 at present. The Planck constant measured with the joule balance is h = 6.6261041(470) × 10 −34 Js. The relative difference between the determined h and the CODATA2010 recommendation value is 5×10 −6 . Further improvements are still being carried out on the NIM-1 apparatus. At the same time, the design and construction of a brand new and compact joule balance NIM-2 are also in progress and presented here. Index Terms-International system of units (SI), joule balance, kilogram, Planck's constant, redefinition, uncertainty.0018-9456

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Measurement and control of the movable coil position of a joule balance with a system based on a laser heterodyne interferometer

Cited by 25 publications

References 7 publications

Absolute Position Sensing Based on a Robust Differential Capacitive Sensor with a Grounded Shield Window

Absolute Position Sensing Based on a Robust Differential Capacitive Sensor with a Grounded Shield Window

Coils and the Electromagnet Used in the Joule Balance at the NIM

The Improvement of Joule Balance NIM-1 and the Design of New Joule Balance NIM-2

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