CURRENT SWITCH WITH AUTOMATIC CALIBRATION
First Claim
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1. A method of monitoring a drive signal having a variable frequency and a variable current, said method comprising the steps of:
- (a) dividing a spectrum of said variable drive signal frequencies into a plurality of frequency ranges each bounded by a lower frequency and an upper frequency;
(b) substantially contemporaneously sampling a current and a frequency of said drive signal;
(c) determining a first frequency range that includes said drive signal sample frequency; and
(d) activating an alarm if said drive signal sample current exceeds by a predetermined magnitude a current of a temporally prior sample of said drive signal having a frequency within said first frequency range.
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Abstract
A current switch that can be reset when it is not powered automatically calibrates itself when the circuit monitored by the current switch is energized.
14 Citations
24 Claims
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1. A method of monitoring a drive signal having a variable frequency and a variable current, said method comprising the steps of:
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(a) dividing a spectrum of said variable drive signal frequencies into a plurality of frequency ranges each bounded by a lower frequency and an upper frequency; (b) substantially contemporaneously sampling a current and a frequency of said drive signal; (c) determining a first frequency range that includes said drive signal sample frequency; and (d) activating an alarm if said drive signal sample current exceeds by a predetermined magnitude a current of a temporally prior sample of said drive signal having a frequency within said first frequency range. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of calibrating a current switch monitoring a drive signal having a variable frequency and a variable current, said method comprising the steps of:
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(a) dividing a spectrum of said variable drive signal frequencies into a plurality of frequency ranges each bounded by a lower frequency and an upper frequency; (b) if a state of a reset control has been changed, accumulating a predetermined number of samples of said drive signal current each having a frequency within a first frequency range; and (c) if said predetermined number of drive signal current samples is accumulated within a predetermined time interval, adopting an approximation said predetermined number of said drive signal current samples as a nominal drive current for said first frequency range. - View Dependent Claims (13, 14)
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15. A current switch for monitoring a drive signal having a variable frequency and a variable current, said current switch comprising:
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(a) a current transducer producing a transducer signal indicating said frequency of said drive signal and indicating a magnitude of said drive signal current; (b) a processing unit for executing a process according to a program instruction; (c) a reset control operable to indicate to said processing unit one of a first state and a second state of said reset control, said indicated reset control state preserved until said reset control is operated to indicate the other of said first state and said second state; (c) a memory storing a program instruction and data including a datum designating an indicated state of said reset control and a datum quantifying at least one drive signal current; and (e) a program instruction stored in said memory and executable by said processing unit, said program instruction causing said processing unit to change a value of said datum quantifying said at least one drive signal current if a state of said reset control presently indicated to said processing unit differs from a state of said reset control stored in said memory.
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16. A current switch for monitoring a drive signal having a variable frequency and a variable current, said current switch comprising:
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(a) a current transducer producing a transducer signal having a frequency related to said frequency of said drive signal and a magnitude related to said current of said drive signal; (b) a processing unit for executing a process according to a program instruction; (c) a memory storing a program instruction and data including a datum quantifying at least one nominal current of said drive signal; and (d) a program instruction stored in said memory and executable by said processing unit, said program instruction causing said processing unit to; (i) determine a frequency and a current of a sample of said drive signal from said transducer signal; (ii) identifying a first frequency range which includes said frequency of said drive signal sample, said first frequency range one of a plurality of frequency ranges comprising a spectrum of potential frequencies for said variable frequency drive signal; (iii) repeating steps (d)(i) and (d)(ii) to accumulate a predetermined number of samples of said drive signal current each having a frequency within said first frequency range; and (iv) if said predetermined number of samples is accumulated within a predetermined interval of time, adopting as a nominal drive signal current for said first frequency range an approximation of said predetermined number of said samples of said drive signal current. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24)
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Specification