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High Resolution Sensors
Linear Variable Differential Transformers (LVDTs)Based on the principle of magnetic induction.
Principle diagram of an LVDT sensor.
A magnetic core, attached to the moving part, determines the amount of magnetic energy induced from the primary windings into the two differential secondary windings. The carrier frequency is typically 10 kHz.
Resolution: up to 10 nm
Repeatability: up to 0.1% of nominal displacement
Bandwidth: up to 1 kHz
Advantages:
- good temperature stability
- very good long term stability
- controls the position of the moving part rather than the position of the Piezo stack
- cost effective
Other features
- outgassing of insulation materials may limit applications in UHV
- extra space for mounting required
P-780, P-721.10, P-762 (click here for "Piezo Flexure NanoPositioners" section).
Capacitive Position Sensors
Based on the capacitance between two plates.
The sensor consists of two RF excited plates that are part of a capacitive bridge. One plate is fixed, the other plate is connected to the object to be positioned. The distance between the plates is inversely proportional to the capacitance which is a measure for the displacement. Resolution on the order of picometers is achievable with short range capacitive position sensors. (See "Capacitive Displacement Sensors" section for details).
Resolution: better than 0.1 nm
Repeatability: up to 0.1 nm
Bandwidth: up to 10 kHz
Advantages:
Other features:
Examples:
P-500 series of Flexure Stages ("Piezo Flexure NanoPositioners" section), P-410 series of Piezo Translators ("Piezo Actuators" section).
Resolution of PI D-015 Capacitive Position Sensor compared to interferomenter.
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