Flow detection apparatus
First Claim
1. Flow-detecting apparatus including means forming a liquid flow passage, an alternating excitation source, means for developing an excitation pattern in liquid in a region in said passage and for sensing said excitation pattern, said pattern developing and sensing means including (a) excitation electrode means connected to said excitation source and (b) sensing electrode means, a flow-driven tracker having at least one pattern-distorting element movably cyclically through said region, signal-receiving means connected to said sensing electrode means for providing an output signal that is alternately in phase with or out of phase with the output of the excitation source during cyclic movement of the tracker, and flow-representing signal means including gating means for combining the output of said alternating excitation source with the output of said signal-receiving means to provide trains of signals and signal-interruption intervals representing cyclic movement of said pattern-distorting element past the sensing electrode means and the excitation electrode means.
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Abstract
The disclosed flow-detecting apparatus involves gating of phase-related excitation and sensed signals from electrodes close to a flow-activated tracker in a liquid passage. A high gain comparator provides peak-limited signals to the phase-comparison gate. In one form, a pair of excitation electrodes are symmetrical in relation to a single sensing electrode. That electrode supplies a sensed signal to one comparator input, the other comparator input having fixed bias. In another form, a pair of sensing electrodes are disposed in an excitation pattern between a localized excitation electrode and a metal pipe that forms the passage and acts as a second excitation electrode. The sensed signals reach respective input terminals of a high-gain comparator and it responds to the difference between the inputs. Other configurations of the electrodes and their excitation are disclosed, including one that promotes rejection of common-mode spurious signals. A comparator that receives flow-representing signals is stabilized against electrical unbalance by a negative feedback loop having a long time constant. In flow-detection apparatus having a multiple-rotor flow-sensing probe, separate flow-detection circuits are used for the respective rotors. The outputs of the flow-representing circuits are combined. Use of different excitation frequencies for those flow-detection circuits adds assurance of non-interfering operation of the flow-detection circuits.
66 Citations
28 Claims
- 1. Flow-detecting apparatus including means forming a liquid flow passage, an alternating excitation source, means for developing an excitation pattern in liquid in a region in said passage and for sensing said excitation pattern, said pattern developing and sensing means including (a) excitation electrode means connected to said excitation source and (b) sensing electrode means, a flow-driven tracker having at least one pattern-distorting element movably cyclically through said region, signal-receiving means connected to said sensing electrode means for providing an output signal that is alternately in phase with or out of phase with the output of the excitation source during cyclic movement of the tracker, and flow-representing signal means including gating means for combining the output of said alternating excitation source with the output of said signal-receiving means to provide trains of signals and signal-interruption intervals representing cyclic movement of said pattern-distorting element past the sensing electrode means and the excitation electrode means.
- 27. In a fluid-flow detector, amplitude-to-phase conversion apparatus including a signal comparison device having negative and positive inputs such that an input signal applied only to the positive input develops a like output and the same input signal applied only to the negative input develops inverse output from the signal comparison device, and means for concurrently applying periodic input signals having in-phase peaks of like polarity to said inputs of the comparison device wherein the amplitude of peaks of a particular polarity of the applied signals is higher at one of said inputs at times and higher at the other of said inputs at times, said signal applying means including means responsive to fluid flow, whereby the output of the signal comparison device becomes alternately high and low in dependence on which of the inputs has the higher applied signal of the particular polarity.
Specification