Method and device for correcting the output signal from a digital transducer for measuring a physical magnitude or variable
OwnerTor Lennart Bernt Griverusinventor
Life of this patent
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Abstract
A method and circuit is provided for correcting an output signal pulse train received from a digital transducer representing a physical magnitude. In a graph the relationship of pulse frequency versus said magnitude will be illustrated by a straight line which will not, due to various influences, intersect the origin of the graph but will pass on either side thereof. By superimposing (adding or subtracting) correction pulses on the transducer pulses, said line is displaced and caused to intersect the origin, said relationship thus being changed to a directly proportional one. Conditions for proper superimposition are defined and an electronic circuit for fulfilling the conditions in a simple and reliable way is disclosed.
Claims11
A method for correcting an output signal from a digital transducer for measuring a physical magnitude, wherein said output signal is a pulse train of frequency f.sub.g, the transducer frequency f.sub.g being essentially a straight line function of said physical magnitude within the working range of said transducer, said transducer having the inherent quality that in a graphical portrayal of said function including axes representing the transducer frequency and said physical magnitude an extension of said straight line beyond said working range cuts said transducer frequency axis at a point to one side of the zero point of such axis, said method including the step of superimposing a correction pulse frequency of f.sub.k on said transducer pulse frequency f.sub.g to thereby obtain a corrected transducer pulse frequency f.sub.g korr, wherein said corrected transducer pulse frequency f.sub.g korr is also graphically portrayable as a straight line function of said physical magnitude, said method including the further step of adjusting said correction frequency f.sub.k such that said straight line representation of said corrected transducer pulse frequency f.sub. g korr cuts substantially through said zero point, the method further comprising:
- a. providing a base pulse train of a predetermined frequency;
- b. dividing said base pulse train into at least two pulse subtrains, the pulses of one subtrain being displaced in time in relation to the pulses of the other subtrain;
- c. said transducer pulses gating pulses of one of said subtrains to produce correction pulses;
- d. said transducer pulses also gating pulses of the second of said subtrains to produce for each transducer pulse a predetermined number of secondary transducer pulses;
- and
- e. superimposing said correction pulses and secondary transducer pulses to obtain a resultant corrected pulse train of a frequency whose function of said physical magnitude is graphically represented by a straight line substantially cutting through said zero point.
A device for correcting an output signal formed as a pulse train and which includes a digital transducer for measuring a physical magnitude and producing a pulse frequency f.sub.g indicative of the measured physical magnitude, the transducer pulse frequency f.sub.g being essentially a straight line function of said physical magnitude within the working range of said transducer, said transducer having the inherent quality that an extension of said straight line outside said working range cuts the transducer frequency axis at a place to one side of the transducer frequency zero point, said device further comprising:
- a base pulse generator for generating pulses at a base frequency;
- a pulse train transmitter fed by said base pulse generator for producing at least two pulse subtrains, the pulses of one subtrain being displaced in time in relation to the pulses of the other subtrain;
- first gating and converting means responsive to a said transducer pulse for controllably feeding parts of one of said pulse subtrains for producing correction pulses at a correction frequency n.multidot.f.sub.k, n being a positive number;
- second gating and converting means also responsive to said transducer pulse for controllably feeding parts of the second of said pulse subtrains for producing secondary transducer pulses at a frequency n.multidot.f.sub.g ;
- and
- an addition unit for producing a corrected pulse train including the secondary transducer pulses and the correction pulses to obtain a corrected transducer pulse frequency n.multidot.f.sub.g korr = n.multidot.f.sub.k + n.multidot.f.sub.g, or f.sub.g korr = f.sub.k + f.sub.g, the value of f.sub.k being determined such, by said first gating and converting means, that the resulting f.sub.g korr characteristic cuts essentially through said zero point.
Dependencies are inferred from the claim text.