High-precision horizontally directed force measurements for high dead loads based on a differential electromagnetic force compensation system

Abstract

In this paper, we present an application for realizing high-precision horizontally directed force measurements in the order of several tens of nN in combination with high dead loads of about 10 N. The set-up is developed on the basis of two identical state-of-the-art electromagnetic force compensation (EMFC) high precision balances. The measurement resolution of horizontally directed single-axis quasi-dynamic forces is 20 nN over the working range of ±100 μN. The set-up operates in two different measurement modes: in the open-loop mode the mechanical deflection of the proportional lever is an indication of the acting force, whereas in the closed-loop mode it is the applied electric current to the coil inside the EMFC balance that compensates deflection of the lever to the offset zero position. The estimated loading frequency (cutoff frequency) of the set-up in the open-loop mode is about 0.18 Hz, in the closed-loop mode it is 0.7 Hz. One of the practical applications that the set-up is suitable for is the flow rate measurements of low electrically conducting electrolytes by applying the contactless technique of Lorentz force velocimetry. Based on a previously developed set-up which uses a single EMFC balance, experimental, theoretical and numerical analyses of the thermo-mechanical properties of the supporting structure are presented.

Detection and characterization of elongated bubbles and drops in two-phase flow using magnetic fields

“…The force measurements are performed with an electromagnetic force compensation (EMFC) balance [24][25][26], which is a state-of-the-art monolithic weighing cell. To measure the horizontal drag forces the EMFC balance is arranged at an angle of 90 degrees in comparison to the normal case of application.…”

Deploying the high-power pulsed lasers in precision force metrology -- SI traceable and practical force quantization by photon momentum

“…To resolve this problem, irrespective of the absence of such a standard, we previously attempted [12], [13] to carry out force measurements and explore possibilities of reversed measurement routine by referencing them by SI-traceable optical power measurements, with no goal of making a comprehensive uncertainty budget assessment of the measurements. We used an early developed prototype with two force sensors (FMS) adapted for differential force measurements [30]. With this FMS, the noise level was reduced by one order of magnitude from below 1 µN level for a single sensor to below 100 nN for a differential signal with 20 nN resolution.…”

Research on Vacuum Transfer Equipment in NIM

“…Step 5: Open the second valve (the left valve) and move the primary standard from the horizontal motion mechanical arm to the supporting in the joule balance. Because of the long distance of horizontal movement, two laser displacement sensors are installed in the joule balance to help accurate positioning [15], [16]. The figure 11 shows the situation.…”