A force sensor utilizing a transformer concept with a ferrofluid core was developed. A ferrofluid reservoir was machined out of Teflon and the open top of the reservoir was sealed with a thin silicone membrane. Forces applied to the silicone membrane caused the membrane to deflect, resulting in the displacement of the ferrofluid in the reservoir through an external tube. The ferrofluid in the tube acted as the core of voltage transformer. The ferrofluid core was excited by an alternating current across a wire coil wound around the tube. A secondary coil was wound around the top portion of the tube which was vertically oriented. As the ferrofluid level in the tube rose in response to applied forces, the secondary coil became engaged by the magnetized ferrofluid, resulting in a voltage induced in the secondary coil that varied with the level of the ferrofluid. The sensor was characterized by the relationship between the forces applied to the membrane and the output voltage readings across the secondary coil in loading and unloading cycles. This relationship was found to be nonlinear and following a negative second-degree polynomial relationship. The sensor was tested at three primary frequencies of 60, 100 and 120 kHz. It was found that 13% of the 5 V A/C exciting voltage applied across the primary coil at 60 kHz was induced into the secondary coil when it was fully engaged by the magnetized ferrofluid. It was determined that the sensor generates the highest sensitivity of 68.3 mV/N over the effective range of 0.1–2.5 N at 60 kHz. The sensor was analyzed for error and the characteristic error was found to be comparable to existing inductive sensors. Sources of most significant of error were identified and proposals for improvements to future designs of this sensor type are provided.

开发了一种利用带有铁磁芯的变压器概念的力传感器。将铁磁流体容器从Teflon机加工出来，并用硅树脂薄膜密封容器的开口顶部。施加到有机硅膜上的力使膜发生挠曲，从而导致铁磁流体通过外管在储液器中移位。管中的铁磁流体充当了变压器的核心。穿过缠绕在管上的线圈上的交流电激励铁磁流体芯。将次级线圈缠绕在垂直定向的管的顶部周围。当管中的铁磁流体液位因施加的力而上升时，次级线圈就被磁化的铁磁流体啮合，导致次级线圈中感应的电压随铁磁流体的水平而变化。传感器的特征在于，在加载和卸载循环中，施加在膜片上的力与次级线圈两端的输出电压读数之间的关系。发现该关系是非线性的并且遵循负的二次多项式关系。该传感器在60、100和120 kHz的三个主要频率下进行了测试。发现在磁化铁磁流体完全啮合时，以60 kHz的频率施加在初级线圈上的5 VA / C励磁电压中有13％被感应到次级线圈中。确定在60 kHz的有效范围0.1–2.5 N范围内，传感器产生的最高灵敏度为68.3 mV / N。对传感器进行了误差分析，发现特征误差与现有​​的电感式传感器相当。确定了最重要的错误源，并提供了改进此传感器类型未来设计的建议。