Measuring the Position and Vibration Displacement of Small Targets Using the Accumeasure 9000 Capacitance Transducer Amplifier

Topics Covered

Introduction
Position and Vibration Displacement Measurement
Capacitance Transducer Amplifier
Results
Conclusion
About MTI Instruments

Introduction

With recent developments in manufacturing, science and technology sectors, it is now possible to determine both the position and vibration displacement of compact mechanical components and assemblies.

These systems are known to work at high speed with comparatively small movements, and therefore decree the use of noncontact sensors. These sensors help ensure that the natural movements are not affected in any way, which is commonly associated with contacting sensors. Moreover, the noncontact sensors must be extremely small and should display a smaller spatial sensing capability.

Position and Vibration Displacement Measurement

In one particular application, taut wires measuring 0.002" to 0.005" in diameters were used whose position and vibration displacement amplitude had to be determined. For this purpose, a wide range of traditional noncontact sensors were used that use optical, magnetic and capacitance technology. However, when these sensors failed to deliver the desired result, the customer approached MTI Instruments to provide a suitable solution for this problem.

Capacitance Transducer Amplifier

MTI Instruments has recently developed the AccumeasureT 9000 capacitance transducer amplifier (Figure 1), which is capable of operating with up to 100 fold smaller capacitance sensing area when compared to most former capacitance sensors. This sensor also maintains acceptable levels of sensing range and standoff distance.

Figure 1. AccumeasureT 9000 capacitance transducer amplifier

Engineers at MTI Instruments leveraged these capabilities to design a capacitance sensor equipped with a sensing electrode measuring just 0.005" and 0.050" in width and length, respectively. When this sensor was used with the Accumeasure 9000 amplifier, it can provide the required sensing range of up to 0.008" for the specified application.

The 0.005" wide dimension and the 0.050" length dimension of the sensing element are aligned with the 0.003" diameter and the axial length of the wire target, respectively. With a sensor of this size, former capacitance transducer amplifiers can give only 0.0005" range, which would not be sufficient to meet the customer's requirement.

Results

Figure 2 shows the dimensions of the sensor; Figure 3 displays the gap response; Figure 4 depicts the lateral sensitivity when operating at 0.005" standoff distance; and Figure 5 shows an outline of the electric field lines running from the sensing electrode to the wire.

Figure 2. Sensing element size

Figure 3. Gap response to 0.003" diameter wire

Figure 4. Cross axis sensitivity at 5.0 MILS gap

Figure 5. Electric field lines from sensor to wire

Conclusion

Thanks to the unique capabilities of the Accumeasure 9000 capacitance transducer amplifier, application engineers at MTI Instruments were able to solve different and complex applications for customers in a range of engineering, research and manufacturing fields.

About MTI Instruments

MTI Instruments is a worldwide leader in the design, manufacture and engineering of non-contact measurement systems and sensors.

MTII’s main products consist of computerized general gauging instruments for position, displacement, thickness and vibration applications based on laser triangulation, fiber-optic and capacitance measurement technologies.

The Semiconductor Products sensor group manufactures manual, semi-automated and fully automated wafer characterization tools designed to measure wafer thickness, total thickness variation (TTV), bow, warp and flatness of semi-insulating and semiconducting materials.

MTII’s Aviation Balancing Instruments group provides state-of-the-art portable balancing and vibration analysis systems for turboprop and jet aircraft engines.

This information has been sourced, reviewed and adapted from materials provided by MTI Instruments.

For more information on this source, please visit MTI Instruments.

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