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| | | Theory of Operation | | |
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| | | If a voltage is applied to one plate of a parallel plate capacitor supplier, an electric field between the plates will be established. This field is the result of the difference between the electrical charges that are stored on each plate. Capacitance refers to the ability of these two plates to hold a charge. MTII's Accumeasure systems measure distance, displacement or motion by converting this capacitance to a linear output voltage. Capacitance is determined by the plate area (A), plate separa | | By design, the probe tip is completely surrounded by a "guard" ring precisely driven at the same potential and phase as the probe sensing area. Not only does this eliminate any external influences from noise but it also eliminates "fringing" of | | |
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| | the field to the target being measured. Linearity exceeding 0.01% of the full scale measurement range is attainable with this approach. | | |
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| | | Current Path | | |
| | | Guard Ring | | |
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| | | — Ground | | |
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| | | The standard measurement range of a probe is proportional to the area of the sensing element. The greater the area, the larger the measurement range and operating distance. During factory calibration special adjustments can be made to the amplifier to increase the measurement range by as much as 60 times. Care must be taken as linearity, resolution and accuracy may be affected. Contact MTII's application engineers for more details. MTII also offers a unique "push/pull" capacitance technology for measurement of non-electrically grounded targets. It is ideal for applications where the target ground path becomes inconsistent or nonexistent, such as air bearing specifications shafts or spindles manufacturers. This revolutionary concept utilizes two probes built into one probe body. One probe "pushes" current while the other "pulls" current. With this arrangement the electrical ground path always remains constant, eliminating the adverse effects of poorly grounded systems. | | |
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| | D (Gap) | | |
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| | | dielectric properties (6) of the material between the plates. | | |
| | | — Ground | | |
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| | | In a typical system the capacitance probe acts as one of the plates while the target being measured acts as the other. The dielectric properties of the material within the gap typically remain constant along with the area of the probe; therefore, the only variable causing a capacitance change is the probe-to-target distance. Using a patented approach, MTII's Accumeasure systems convert this changing capacitance into a linear voltage proportional to the probe gap. The amount of voltage change for a given gap change is called the sensitivity. To maintain a highly linear response it is important to establish a uniform electric field in the gap. To accomplish this MTII uses a "guarded" probe approach. | | |
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| | | Bearing Defect Leveling or Flatness Thread Quality Analysis Measurements Inspection | | |
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