Electronic hazard tester for medical facilities

Claim 2

An electronic test instrument for measuring electrical parameters within an electrically susceptible patient location (ESPL), said ESPL having a patient ground and a plurality of electrically conductive surfaces therein, comprising: a. a chassis; b. probe means connected to and operatively extendable from said chassis to each of said conductive surfaces for sensing electrical parametric conditions of said surfaces when in electrical contact therewith; and c. electronic circuit means mounted to said chassis for measuring and for determining hazardous electrical conditions within said ESPL, said circuit means comprising: i. a signal input operatively connected with said probe means for receiving said sensed electrical conditions therefrom; ii. reference means operatively connecting circuits within said electronic circuit means with said patient ground for electrically referencing the circuits thereto; iii. current measurement means operatively connected with said signal input to receive said sensed electrical conditions therefrom, for measuring electrical current flow potentially available through an electrically susceptible patient from said conductive surface probed by said probe means to said patient ground; iv. hazard detector means operatively connected with said current measurement means for providing a warning output signal when the magnitude of said measured electrical current flow exceeds a predetermined microshock hazard level; and v. resistance measurement means in circuit with said signal input for measuring the electrical resistance between said patient ground and any of said electrically conductive surfaces operatively contacted by said probe means, by causing current flow through that conductive surface in contact with said probe means to said patient ground, and by analyzing electrical characteristics of such caused current flow, said resistance measurement means further having means for variably limiting the magnitude of said caused current to levels predetermined as non-hazardous to an electrically susceptible patient within the ESPL.

Claim 3

An electrical test instrument according to claim 1, wherein said chassis defines an internal cavity for enclosedly retaining said probe means when not in operative use; and wherein said probe means comprises: a. a single electrical probe suitable for making electrical contact with said conductive surfaces; and b. conductor means for electrically connecting said probe with said signal input of said electronic ciRcuit means, said conductor means being of circuit means, said conductor means being of sufficient length to enable said probe to operatively contact all of said conductive surfaces within said ESPL.

Claim 4

An electronic test instrument according to claim 1, wherein said current measurement means comprises: a. resistor circuit means operatively connected between said signal input and said patient ground for providing an electrical path therebetween, said resistor circuit means having an equivalent resistive value between said signal input and said patient ground simulating a minimum electrical resistance of an electrically susceptible patient; and b. operational amplifier means operatively connected with said resistor circuit means for sensing the magnitude of current flow therethrough and for providing an output signal that varies proportionately with the magnitude of said sensed current flow.

Claim 5

An electronic test instrument according to claim 3, wherein said current measurement means, further comprises: a. read-out means operatively connected to receive said output signal of said operational amplifier means for providing a visual quantitative readout thereof; and b. selector means operatively connected with said operational amplifier means for providing said read-out means with variable range sensitivity.

Claim 6

An electronic test instrument according to claim 3, wherein said operational amplifier means comprises first and second operational amplifier circuits electrically serially connected for amplifying said sensed current flow signal through said resistor circuit means, and variable gain selector means operatively connected to simultaneously selectively vary the gain of both said first and second operational amplifier circuits for providing accurate cross-checking of their respective individual operations.

Claim 7

An electronic test instrument according to claim 3, wherein said hazard detector means comprises: a. operational amplifier means operatively connected with said resistor circuit means of said current measurement means for sensing the magnitude of AC current flow therethrough and for providing a first output signal whenever the magnitude of said sensed AC signal is less than said predetermined microshock hazard level and for providing said warning output signal whenever the magnitude of said sensed AC signal exceeds said predetermined microshock hazard level; and b. warning means operatively connected to receive said first output and said warning output signals for providing a sensory warning indication within the ESPL whenever said warning output signal is received thereby.

Claim 8

An electronic test instrument according to claim 1, wherein said ESPL has at least one wall into which said patient ground extends, wherein a portion of said chassis is configured for mounting within said one wall, wherein said reference means extends within said one wall for operatively connecting the circuits within said electronic circuit means to that portion of said patient ground extending therein, wherein said chassis includes a control panel forming one surface thereof and configured for substantially flush mounting with the surface of said one wall, and wherein said probe means is operatively connected to extend from said control panel.

Claim 9

An electronic test instrument according to claim 1, wherein said resistance measurement means comprises: a. current source means having an output, for supplying a flow of current having constant predetermined magnitude from its said output whenever an electrical return path is connected between its said output and said patient ground; b. electrical return path means operatively connecting said current source means outut with said signal input and with said patient ground for causing a controlled portion of the current flowing from said current source means output to flow through and out of said probe means whenever said probe means operatively contacts one of said conductive surfaces, saId electrical return path means including said means for variably limiting said caused controlled current flow directed out of said probe means to a magnitude not exceeding said non-hazardous current level; c. means operatively connected with said electrical return path means for sensing the magnitude of said caused current flowing out of said probe means and for providing an output signal proportional thereto; and d. indicator means operatively connected to receive said last named output signal for providing in response thereto a visual indication accurately displaying the magnitude of that electrical resistance of the electrical return path between said probe means and said patient ground and external of said electronic test instrument.

Claim 10

An electronic test instrument according to claim 8, wherein said electrical return path means comprises: a. first electrical path means operatively connecting said constant current source output with said patient ground for providing a current flow path therebetween having a known predetermined resistive value; and b. second electrical path means operatively connecting said signal input with said constant current source output for providing a second current flow path for said current flowing from said current source means output whenever said probe means is in operative electrical contact with one of said conductive surfaces, and for cooperating with said first electrical path means to controllingly divide said constant current flow therebetween responsive to the electrical resistance of said second electrical path means and to limit the level of current flow through said second electrical path means to said non-hazardous current level.

Claim 11

An improved electronic ohmmeter for measuring the electrical resistance between a patient ground bus and a second ground terminal conductor extending from and in direct electrical contact with said patient ground bus within an electrically susceptible patient location (ESPL), comprising: a. current source means electrically referenced to said patient ground bus and having an output, for providing constant current flow from said output whenever an electrical return path is connected between said output and said patient ground bus; b. first electrical path means operatively connecting said constant current source output with said patient ground bus for providing a first electrical return path therebetween, said first electrical path means being of predetermined electrical resistance; c. probe input means operatively connected to said constant current source output and adapted for operatively electrically contacting said second ground terminal conductor for providing therewith a second electrical return path for said current flow from said current source output whenever said probe input means in in operative electrical contact with said second ground terminal conductor, said first electrical path means and said probe input means being cooperatively operable to proportion said constant current flow therebetween as a function of their respective equivalent resistive values as measured between said constant current source output and said patient ground bus, and proportioned such that the maximum level of that portion of said constant current which flows out of said probe input means is of a magnitude predetermined to be non-hazardous to an electrically susceptible patient within the ESPL; d. voltage sensing means connected to continuously monitor the voltage level at said constant current source means output for providing a sensed output signal varying in response thereto; e. operational amplifier circuit means operatively connected to receive said sensed output signal for providing an amplified output signal the amplitude of which varies proportionately with said sensed output signal; and f. indicator means operatively connected to receive said amplified output signal for providing a visual indication responsive thereto, accurately representing thE electrical resistance of that part of said second electrical return path located external of said ohmmeter and between said probe input means and said patient ground bus.

Claim 12

An improved electronic ohmmeter for measuring the electrical resistance between a patient ground bus and a second ground terminal conductor extending from and in direct electrical contact with said patient ground bus within an electrically susceptible patient location (ESPL), comprising: a. current source means electrically referenced to said patient ground bus and having an output, for providing constant current flow from said output whenever an electrical return path is connected between said output and said patient ground bus; b. first electrical path means operatively connecting said constant current source output with said patient ground bus for providing a first electrical return path therebetween, said first electrical path means being of predetermined electrical resistance; c. probe input means operatively connected to said constant current source output and adapted for operatively electrically contacting said second ground terminal conductor for providing therewith a second electrical return path for said current flow from said current source output whenever said probe input means in in operative electrical contact with said second ground terminal conductor, said first electrical path means and said probe input means being cooperatively operable to proportion said constant current flow therebetween as a function of their respective equivalent resistive values as measured between said constant current source output and said patient ground bus, and proportioned such that the maximum level of that portion of said constant current which flows out of said probe input means is of a magnitude predetermined to be non-hazardous to an electrically susceptible patient within the ESPL; d. voltage sensing means connected to continuously monitor the voltage level at said constant current source means output for providing a sensed output signal varying in response thereto; e. operational amplifier circuit means operatively connected to receive said sensed output signal for providing an amplified output signal the amplitude of which varies proportionately with said sensed output signal; and f. indicator means operatively connected to receive said amplified output signal for providing a visual indication responsive thereto, accurately representing thE electrical resistance of that part of said second electrical return path located external of said ohmmeter and between said probe input means and said patient ground bus.

Claim 13

An improved electronic ohmmeter according to claim 9, wherein said operational amplifier circuit means includes means for adjusting the gain of said operation amplifier circuit means to correctively compensate said amplified output signal for causing said indicator means to accurately represent said electrical resistance of that said part of the second electrical return path located external of the ohmmeter, regardless of the electrical resistance of said probe input means.

Claim 14

An improved electronic ohmmeter according to claim 10, wherein said probe input means comprises: a. a single electrical probe suitable for making electrical contact with said second ground terminal conductor; and b. variable resistance means operatively serially connecting said electrical probe with said constant current source means output for providing an electrical path of presettable resistive value therebetween.

Claim 15

An improved electronic ohmmeter according to claim 12, including circuit protection means operatively connected with said probe input means for protecting said operational amplifier circuit means from large voltage levels and spikes applied to said probe input means.

Claim 16

An improved electronic ohmmeter according to claim 13, wherein said circuit protection means includes: a. fuse means electrically connected in series between said electrical probe and said patient ground bus for opening the electrical path between said electrical probe and said operational amplifier circuit means whenever a current of predetermined magnitude and duration flows therethrough; and b. variable energy dissipating means connected in series between said variable resistance means and said operational amplifier circuit means for preventing the application of current surges in said sensed output signal to said operational amplifier circuit means.