Pulsed coil drive circuit for a sampled inductive transducer
A technology of pulse coils and transducers, applied in the direction of using electric/magnetic devices to transfer sensing components, using electric devices, using electromagnetic means, etc., can solve the problems of increasing the cost of charge pump circuits, etc., and achieve high current carrying capacity and beneficial effect on accuracy, reducing the number of
Active Publication Date: 2008-05-28
MELIUS
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Thus, for pulsed excitation, energy recovery becomes possible, but at an increased cost of the charge pump circuit, which itself requires at least one additional capacitor
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[0019] The circuit shown in Figure 1 includes a series circuit consisting of a transducer drive coil L1 and a storage capacitor C1. The series circuit can be open or connected to voltage V through switch S1 1 or connected to voltage V via switch S2 2 . The voltage across coil L1 and capacitor C1 in series is VL, and the voltage across capacitor C1 alone is VC. The voltage VP induced on the transducer sense coil L2 is stored on the sampling capacitor C2 as the voltage VS sampled by the sampling switch S3. The waveforms in Figure 1 illustrate the operation of the circuit, from top to bottom: switches S1, S2, S3 open (below) or on (above), sharing the same voltage scale for voltages VL and VC, The coil current I, the induced voltage VP and the sampled voltage VS share the same voltage scale. The dashed line shows the waveform of a lossless circuit, hereinafter referred to as the ideal circuit, and the solid line shows the waveform of a circuit with resistive elements, ie the ...
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The pulsed coil drive for a sampled inductive transducer has at least one of its drive coils forming a series circuit with a capacitor whose free terminal is connected to the negative terminal of a voltage source. This series circuit is normally open, i.e. has no current during the intervals between pulses. Sampling occurs once per pulse and needs a minimum time for the sampled signal to settle to the required accuracy. Each pulse's sampling interval is preceded by a pre-sampling interval and followed by a post-sampling interval. The supply voltage is applied across the series circuit during both the pre- and post-sampling intervals by switching the coil's free terminal to the voltage source's positive terminal through a p-channel mosfet. During the sampling interval, the series circuit is shorted by switching the coil's free terminal to the voltage source's negative terminal through an n-channel mosfet. The resulting coil current ramps from zero to a positive peak current before sampling, then to a negative peak current during sampling and back to zero after sampling. Most of the magnetic energy is thus recovered, instead of being dissipated after the pulse, and resistive losses are reduced.
Description
technical field [0001] The present invention relates to a pulse coil drive for sampled inductive transducers. Such intermittently operating transducers are required in applications where a compromise is made between the high frequency or bandwidth of an inductive transducer and the required low power consumption. Typically, they are used in small battery-operated measurement tools such as calipers, micrometers and dial indicators: they have pulse widths of less than 100 ns, and their bandwidths are several MHz. Their relatively low pulse or sampling rate (samples per pulse) of about ten thousand times per second limits their power consumption to a few hundred microwatts. Background technique [0002] As in US Pat. No. 4,446,427 to Lovrenich, the pulses may be damped oscillations that utilize the inductors and capacitors of the transducer to form a resonant circuit and to periodically initiate oscillations. The first voltage peak of the damped oscillation is sampled by a pe...
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Inventor 汉斯·乌尔里希·迈尔
Owner MELIUS