Digital loop detector with improved detection control
First Claim
1. In a digital detector device for detecting a metal object in the field of influence of a detector loop controlling the frequency of pulses created by an oscillator, said digital detector device including counter means for counting said pulses created by said oscillator during a counting interval having a selected duration whereby the magnitude of the pulses counted during said controlled interval is indicative of the inductance of said loop and digital means for creating an output signal when the number of pulses counted by said counter means for a given counting interval differs from a selected count by a number greater than a selected threshold number, the improvement comprising:
- said digital means including means for creating a binary coded signal having a series of binary bits arranged in a selected order for indicating the difference between said number of counted pulses and said selected count;
a binary logic circuit having a plurality of input lines individually corresponding to said bits and divided into first and second groups, an output line and means for creating said output signal in said output line when the logic on one of said input lines is at a selected binary logic value;
a source of binary logic value opposite to said selected binary logic value;
separate sensitivity switch means for selectively shifting said input lines of said first group between a first position where said associated input line has a binary condition controlled by a corresponding one of said binary bits and a second position where said associated input line has a binary condition controlled by said binary logic source;
means for directing bits of binary logic to corresponding input lines of said second group of input lines; and
, means for inhibiting creation of said output signal when a selected one of said input lines in said second group is at said selected binary logic value.
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Abstract
An improvement in a digital device for detecting a metal object in the field of influence of an oscillator controlling loop, which digital device includes counter means for counting pulses during a counting interval, with the magnitude of the pulse count during the interval being indicative of the metal detected by the loop. The improvement includes means for creating a group of binary logic signals indicative of the difference between the pulse count and a selected reference count, these signals are allocated from a least significant to a more significant binary number, and reading means for reading the logic of at least some of the binary logic signals, which reading device includes means for indicating a detection when the signal being read has a selected binary logic pattern.
20 Citations
9 Claims
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1. In a digital detector device for detecting a metal object in the field of influence of a detector loop controlling the frequency of pulses created by an oscillator, said digital detector device including counter means for counting said pulses created by said oscillator during a counting interval having a selected duration whereby the magnitude of the pulses counted during said controlled interval is indicative of the inductance of said loop and digital means for creating an output signal when the number of pulses counted by said counter means for a given counting interval differs from a selected count by a number greater than a selected threshold number, the improvement comprising:
- said digital means including means for creating a binary coded signal having a series of binary bits arranged in a selected order for indicating the difference between said number of counted pulses and said selected count;
a binary logic circuit having a plurality of input lines individually corresponding to said bits and divided into first and second groups, an output line and means for creating said output signal in said output line when the logic on one of said input lines is at a selected binary logic value;
a source of binary logic value opposite to said selected binary logic value;
separate sensitivity switch means for selectively shifting said input lines of said first group between a first position where said associated input line has a binary condition controlled by a corresponding one of said binary bits and a second position where said associated input line has a binary condition controlled by said binary logic source;
means for directing bits of binary logic to corresponding input lines of said second group of input lines; and
, means for inhibiting creation of said output signal when a selected one of said input lines in said second group is at said selected binary logic value.
- said digital means including means for creating a binary coded signal having a series of binary bits arranged in a selected order for indicating the difference between said number of counted pulses and said selected count;
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2. In a digital detector device for detecting a metal object in the field of influence of a detector loop controlling the frequency of pulses created by an oscillator, said digital detector device including counter means for counting said pulses created by said oscillator during a counting interval having a selected duration whereby the magnitude of the pulses counted during said controlled interval is indicative of the inductance of said loop and digital means for creating an output signal when the number of pulses counted by said counter means for a given counting interval differs from a selected count by a number greater than a selected threshold number, the improvement comprising:
- said digital means including means for creating a multiple digit binary representation of the difference between said pulse count and said selected count, said binary representation progressing numerically from a least significant digit to a most significant digit;
a number of output elements;
means for directing the binary logic of each of said digits to corresponding different ones of said elements with a particular element receiving binary logic from said most significant digit;
means for creating said output signal when at least one of a plurality of said elements other than said particular element receives a given binary logic from said directing means; and
, means for selectively preventing selected ones of said elements from shifting to said given binary logic whereby said threshold number is changeable. - View Dependent Claims (3, 4, 5)
- said digital means including means for creating a multiple digit binary representation of the difference between said pulse count and said selected count, said binary representation progressing numerically from a least significant digit to a most significant digit;
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6. In a digital detector device for detecting a metal object in the field of influence of a detector loop controlling the frequency of output pulses of a first variable frequency oscillator, a fixed frequency oscillator means for creating fixed frequency pulses, said detector means including counter means for counting one of said pulses for a counting interval controlled by the other of said pulses to provide a pulse count for a given interval indicative of the frequency of said variable frequency oscillator, the improvement comprising:
- means for creating a group of binary logic signals arranged from numerically least significant to numerically most significant digits and indicative of the numerical difference between said pulse count and a selected reference count;
a group of signal receiving elements, each of said elements receiving a single, different one of said binary logic signals;
a first logic means having a plurality of inputs and an output for creating a given binary logic on said output when one of said inputs receives a selected binary logic;
a plurality of said inputs of said first logic means connected directly to said elements receiving binary logic signals corresponding to said binary signals numerically adjacent said most significant digit;
the remaining inputs of said first logic means each including manually operated switching means having a first condition connecting one of said remaining inputs to elements receiving one of said binary logic signals corresponding to said binary logic signals numerically adjacent said least significant digit and a second condition connecting said one of said remaining inputs to a source of binary logic binarily opposite to said selected binary logic whereby the sensitivity of said first logic means may be varied by said switching means;
a second logic means having an output and a plurality of inputs for creating a detection signal in said output when said inputs each receive a known binary logic signal;
one of said inputs of said second logic means being controlled by said output of said first logic means with said known binary logic of said one input being said given binary logic and another of said inputs of said second logic means being controlled by the binary logic on one of said signal receiving elements, said another input having the known binary logic signal when said group of binary logic signals indicates a detection difference between said pulse count and said reference count.
- means for creating a group of binary logic signals arranged from numerically least significant to numerically most significant digits and indicative of the numerical difference between said pulse count and a selected reference count;
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7. In a digital detector device for detecting a metal object in the field of influence of a detector loop controlling the frequency of output pulses of a first variable frequency oscillator, a fixed frequency oscillator means for creating fixed frequency pulses, said detector means including counter means for counting one of said pulses for a counting interval controlled by the other of said pulses to provide a pulse count for a given interval indicative of the frequency of said variable frequency oscillator, the improvement comprising:
- means for creating in signal receiving elements a group of binary logic signals with the signals on the elements being indicative of the difference between said pulse count and a selected reference count;
logic means with an output and several inputs for creating a detection signal in said output when at least one of said inputs receives a known binary logic signal;
means for connecting certain ones of said inputs directly to ones of said elements; and
switch means for shifting other of said inputs between a first position with said input connected to a source of binary logic opposite to said known binary logic and a second position with said input connected to one of said elements different from said ones of said elements connected directly to one of said inputs of said logic means.
- means for creating in signal receiving elements a group of binary logic signals with the signals on the elements being indicative of the difference between said pulse count and a selected reference count;
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8. In a digital detector device for detecting a metal object in the field of influence of a detector loop controlling the frequency of output pulses of a first variable frequency oscillator, a fixed frequency oscillator means for creating fixed frequency pulses, said detector means including counter means for counting one of said pulses for a counting interval controlled by the other of said pulses to provide a pulse count for a given interval indicative of the frequency of said variable frequency oscillator, the improvement comprising:
- means for creating a group of binary logic signals arranged from numerical least significant to numerical most significant digits and indicative of the numerical difference between said pulse count and a selected reference count;
a binary reading means having an output and several inputs, said binary reading means includes means for shifting said output to a first binary logic condition only when all of said inputs are at a known binary logic;
a detection logic device having an output and inputs and means for shifting said output to a given binary logic condition when said inputs receive selected binary signals;
means responsive to said given binary logic for creating a detection signal;
means for connecting said output of said binary reading means to a first of said inputs of said detection logic device with said first binary logic condition being opposite to the selected binary signal of said first input of said detection logic device;
conductive elements for directing each of said binary logic signals to correspondingly different ones of said several inputs of said binary reading means; and
, manual switch means in said conductive elements which direct the least significant binary logic signals to said inputs of said reading means, said switch means having a manually selected position connecting said element associated with said switch means to a source of the known binary logic for said associated element.
- means for creating a group of binary logic signals arranged from numerical least significant to numerical most significant digits and indicative of the numerical difference between said pulse count and a selected reference count;
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9. In a digital detector device for detecting a metal object in the field of influence of a detector loop controlling the frequency of output pulses of a first variable frequency oscillator, a fixed frequency oscillator means for creating fixed frequency pulses, said detector means including counter means for counting one of said pulses for a counting interval controlled by the other of said pulses to provide a pulse count for a given interval indicative of the frequency of said variable frequency oscillator, the improvement comprising:
- means for creating a group of binary logic signals arranged from numerical least significant to numerical most significant digits and indicative of the numerical difference between said pulse count and a selected reference count;
a binary reading means having an output and several inputs, said binary reading means includes means for shifting said output to a first binary logic condition only when all of said inputs are at a known binary logic;
conductive elements for directing each of said binary logic signals to correspondingly different ones of said several inputs of said binary reading means;
manual switch means in said conductive elements which direct the lesser significant binary logic signals to said inputs of said reading means, said switch means having a manually selected position connecting said element associated with said switch means to a source of the known binary logic for said associated element; and
means for creating a detection signal when said output of said reading means is at a second logic condition opposite to said first logic condition.
- means for creating a group of binary logic signals arranged from numerical least significant to numerical most significant digits and indicative of the numerical difference between said pulse count and a selected reference count;
Specification