Patent Description:
It is known that if a swimmer encounters a body of water with an electric field the swimmer can be electrocuted with a voltage gradient of as little as two volts per foot. The mere presence of the swimmer in the electric field causes the current flowing in the water to take a path of least electrical resistance through the swimmers body since the wet skin on a swimmer's body has a lower electrical resistance than the water surrounding the swimmer. If the voltage gradient is sufficiently high the current flowing through the swimmer's body can electrocute the swimmer. In still other cases a person may be electrocuted if he or she comes into incidental contact with a body of water, which has leakage from an electrical source.

In addition to the existence of a harmful voltage gradient in a body of water there is a need to safely locate the source of the harmful voltage gradient as well as to ensure those proximate the body of water that the water does or does not contain a hazardous electrical field.

Document <CIT> discloses a shock detector having an electrical detector having a set of water immersible electrodes for detecting hazardous water conditions through the determination of the presence of either an electrical current in a body of water, a voltage in the body of water or a voltage gradient in the body of water and then providing an alert to the existence of hazardous electrical conditions in the body of water which in some cases may transmitted to a power source to shut off a power source thereby removing the hazardous water condition.

Document <CIT> discloses a voltage gradient detector that provides notice when a potentially hazardous voltage gradient is present in water, employing at least one pair of spaced-apart electrodes connected to an LED. The electrode spacing is selected such that, when exposed to a sufficiently large voltage gradient, the voltage between the electrodes causes activation of the LED. Sensitivity in multiple directions can be attained by employing a pair of LEDs between the electrodes, and by employing three pairs of electrodes and associated LED pairs, with the pairs of electrodes being spaced apart along substantially orthogonal axes.

An open water shock detector for measuring the existence of a harmful water voltage in a body of water through the measurement of a voltage gradient on a set of water electrodes with the shock detector including a self testing feature to indicate the shock detector is operating properly before full activation of the shock detector so that when the shock detector in an activated condition the shock detector is useable to either alert a person to a harmful water condition or to allow an operate to use the shock detector to isolate the source of an electrical short in the body of water through a displacement of the shock detector in the body of water.

<FIG> shows a free floating, buoyant, open water shock detector <NUM> floating upright in a body of water <NUM> having a water line <NUM> with the upper housing 17a of shock detector <NUM> including a resilient bumper <NUM> located around the outer perimeter of the shock detector. The resilient bumper, which is shown located above the water line <NUM>, protects the shock detector in the event the shock detector accidently bumps into an object while floating in the body of water. In this example, the shock detector <NUM> includes a transparent or see through hemispherical shaped dome <NUM> extending from a top housing 17a, with a green LED light <NUM> and a red LED light <NUM> that are both visible from afar through the transparent dome <NUM>. The lower housing 17b of shock detector <NUM>, which is below the water line <NUM>, is shown partially cut away to reveal a ballast <NUM> in the bottom of shock detector <NUM>. A feature of the invention is the use of a ballast in the bottom of the floating shock detector that causes the shock detector <NUM> to float in the upright condition as shown in <FIG> as well as causes the shock detector to right itself in the event the shock detector is accidently flipped upside down as it floats in the body of water. The ballast may either be a dead weight placed in the floating shock detector or it may be strategically placed integral components of the shock detector so that the weight of the strategically placed external and internal shock detector components comprise the necessary ballast for generating a self righting force or torque to the shock detector <NUM> that is sufficient to return the shock detector to the floating condition as shown in <FIG> in the event the shock detector tips over due to an external force such as a wave. A feature of the open water shock detector <NUM> is that it is ungrounded since it floats in the body of water and measures a voltage gradient within the body of water. A further feature of shock detector <NUM> is that the shock detector housing and dome are both waterproof and weatherproof, which enables the shock detector to operate while floating in a body of water as well as all types of weather.

<FIG> is a bottom view of the floating shock detector <NUM> of <FIG>, which comprises an ungrounded shock detector since it measures voltages between electrodes located in the body of water without reference to an electrical ground. In this example the shock detector determines the presence of a harmful voltage gradient in the body of water as the shock detector free floats in a body of water. The processor in shock detector <NUM> measures voltage between a set of spaced apart water electrodes <NUM>, <NUM> and <NUM>, which are integral to the shock detector, to obtain a voltage difference between the electrodes i.e. a voltage gradient in the body of water and compares to a known voltage gradient that is sufficient to cause injury or death to a person in the body of water. While the shock detector of the invention described herein measures the voltage gradient in the body as it floats in a body of water <NUM> the shock detector may also be attached to a structure such as a dock and used to measure a voltage difference between a water electrode and an earth ground. In either case the shock detector can determine a hazardous water voltage condition i.e. a voltage gradient within the body of water that could injure or kill a person coming into contact with the body of water.

The voltage gradient, which is referred herein as a water voltage, is based on a measured voltage difference between any of the three electrodes or may be computed based on an average of the measured voltage difference between the three water electrodes. In either event the magnitude of voltage gradient in the body of water is a function of whether the voltage gradient can injure or kill a person that comes into contact with the body of water. In the example shown the shock detector <NUM> determines if there is a voltage gradient in the body of water that may injure or kill a person that enters the body of water. A feature of the shock detector <NUM> is that the shock detector can determine the existence of a harmful water voltage gradient in a body of water even though the shock detector is remote from a structure in contact with the body of water. In the example shown the shock detector measures an AC water voltage such as an AC water gradient in the body of water to determine if the water voltage i.e. the AC voltage gradient is such that it would injure or kill a person. In some cases where DC voltages may be present one may measure a DC voltage gradient or in other cases one may measure both AC and DC voltage gradients to determine if the AC or DC water voltage is such that it would injure or kill a person.

<FIG> shows the underside <NUM> of shock detector <NUM> revealing a set of three circular metal water electrodes located on the bottom side of an ungrounded shock detector <NUM> that floats in a body of water. The ungrounded shock detector <NUM> includes, a first water electrode <NUM>, a second water electrode <NUM> and a third water electrode <NUM> with the water electrode <NUM> spaced from the water electrode <NUM> by the distance x and the water electrode <NUM> spaced from the water electrode <NUM> by the distance y with the three electrodes extending through a common plane. In this example the water electrode <NUM> and water electrode <NUM> are located along a right angle with the apex located at water electrode <NUM> and all three water electrodes, which are below the water line, are connected to a processor in shock detector <NUM> that measures the electric potential between electrodes to obtain the voltage gradient (i.e. volts per foot) in the body of water <NUM> to determine whether the voltage gradient in the body of water is such that it could cause injury or kill a person who enters the body of water. While a set of three water electrodes allows one to determine the voltage gradient in different directions in the electric field in some applications one may use a set of two water electrodes to determine the voltage gradient in the body of water and in other applications four or more water electrodes may be used to measure the voltage gradients in the body of water.

<FIG> is a top view of the floating shock detector <NUM> showing the central location of the transparent dome <NUM> with a green LED light <NUM> and a red LED light <NUM> visible through the dome <NUM>. The dome provides enhanced visibility since it allows the LED lights to be seen by a person located laterally of the shock detector or a person located above the shock detector. An audible alarm <NUM> such as a beeper or a buzzer is also located on the top housing 17a of the shock detector. An opening <NUM> in top housing 17a forms a loop that allows one to insert a cord therethrough so one can attach the cord to the shock detector. The cord allows the shock detector <NUM> to be tethered in place in a body of water <NUM> with an anchor or the like. In addition the shock detector may be tethered to a dock or to a boat to alert persons to the existence of a harmful voltage gradient in a range around the floating shock detector. The feature of a tethered floating shock detector is also useful to a boater coming into an unknown dock since the boater can lower the shock detector into the body of water using the cord attached to the shock detector to test for the presence of a harmful electric field in the body of water before stepping out of the boat. A further advantage of a tethered floating shock detector is that when the boat is in open water one can lower the floating shock detector into the water around the boat to determine if there is a harmful electrical field around the boat, which may be caused by an electrical short in the boat wiring. A feature useful in the event persons want to swim from the boat. Thus, the shock detector described herein may be used in water adjacent a land site or in open water to determine if a voltage gradient is present in the water, which is sufficient to injure or kill a person coming into contact with the body of water.

<FIG> is a schematic illustrating electronic communications between various components of the shock detector <NUM> and a circuit board <NUM> containing a processor <NUM>. In this example the audible alarm <NUM> connects to processor <NUM> on circuit board <NUM> through electrical lead 16a. The Red LED light <NUM> or visual alarm connects to processor <NUM> on circuit board <NUM> through electrical lead 13a and similarly the green LED light <NUM> or visual alarm connects to processor <NUM> on circuit board <NUM> through electrical lead 14a.

Located proximate the circuit board <NUM> is a battery <NUM> having a first terminal with a lead 33a connected to processor <NUM> and a second terminal with a lead 33b connected to processor <NUM>. In this example the battery <NUM> provides power to operate the processor <NUM> as well as the visual alarms <NUM>, <NUM> and the audible alarm <NUM>.

The set of water electrodes <NUM>, <NUM> and <NUM> are shown located in a body of water <NUM> with an electrical lead 20a, connecting water electrode <NUM> to processor <NUM>, an electrical lead 21a connecting water electrode <NUM> to processor <NUM> and an electrical lead 22a connecting water electrode <NUM> to processor <NUM> with all the water electrodes located below the water line <NUM>. The use of three water electrodes enables measurement of water voltage in the body of water between three different locations. In this example, the shock detector <NUM> measures the water voltage between three electrodes to obtain a voltage gradient within the body of water.

The voltage gradient in a body of water is generally highest proximate a current leak, which is the source of the electrical failure, and decreases the further away from the source of the electrical failure thus creating a potential field within the body of water that decrease in distance from the source of the electrical failure. In this example the processor <NUM> determines if the strength of the voltage gradient in the body of water is such that it would kill or injure a person coming into contact with the body of water.

A feature of the invention described herein is that before initiating measurements of voltage gradient the shock detector performs a self-test to let a person know the shock detector is operative and ready to be placed in a body of water to determine if the water contains a harmful electrical condition. <FIG> shows a flow chart illustrating the method of self-testing of the shock detector <NUM>, which comprises the steps of checking battery voltage under various conditions before the shock detector begins monitoring the voltage gradient in the body of water to determine if a hazardous electrical condition exists i.e. where the voltage gradient is sufficient to deliver an electric shock that can cause injury or death to a person that comes into contact with the body of water.

To initiate the battery self-test the shock detector processor <NUM> automatically performs a sequence of battery tests under different load conditions. In this example the self-test includes measuring the battery voltage with an open circuit (no load across the terminals of the battery), which is referred to as the open circuit voltage (OCV) test (<NUM>) of the battery in the shock detector. If the OCV voltage of the battery is low (<NUM>) (i.e. below a preselected voltage threshold) the processor <NUM> stops the test (<NUM>) and prevents the shock detector from start up. If the OCV voltage of the battery is good (<NUM>) i.e. above the preset preselected voltage threshold the processor (<NUM>) begins the next step by checking the battery voltage under various load conditions. The first test of the battery voltage under load condition is with the green LED light on as illustrated by the green LED test (<NUM>). If the battery voltage is below the preselected voltage (i.e. bad) with the green LED on, the processor (<NUM>) within the shock detector <NUM> prevents shock detector start up. On the other hand if the battery voltage with the green LED on is above the preselected voltage (i.e. good) (<NUM>) the processor (<NUM>) proceeds to the next step in the battery self test cycle where the battery voltage is tested with the red LED on. If the processor determine the battery voltage with the red LED on is bad (<NUM>), i.e. below a preselected voltage the processor <NUM> stops the operation of the shock detector. If the battery voltage of the shock detector is good with the red LED on (<NUM>) i.e. above the preselected voltage the processer <NUM> sends a signal to start the shock detector (<NUM>) for measuring the voltage gradient in the body of water. Typically, the cycle for self-test where the battery voltage is measured under different conditions may be repeated after start up to ensure that the battery voltage remains sufficient to measure the voltage gradient and emit an alarm over an extended period of time if the shock detector should detect the presence of harmful voltage gradient or if the battery should be replaced.

A further feature of the invention is that once the shock detector <NUM> passes the battery self test the shock detector <NUM> automatically begins monitoring the voltage gradient in a body of water. In operation mode the shock detector <NUM> provides real time information on the existence of harmful voltage gradient in the body of water, the strength of the voltage gradient in the body of water and the status of the battery in the shock detector through a combination of a red LED light, a green LED light and an audio alarm or beeper. This latter feature of measuring the level or strength of the voltage gradient in the body of water enables shock detector <NUM> use as a diagnostic tool to determine the location of a voltage leak in the body of water by moving the shock detector in the body of water to find the region in the body of water where the voltage gradient is the highest since the voltage gradient generally decreases with distance from the source of the leak.

<FIG> is a flow chart of the operation of shock detector <NUM>, which illustrates the method of determining the presence of water voltage as well as the level of the voltage gradient during four field conditions. <FIG> shows that during the voltage-measuring phase the processor begins by measuring the battery voltage (<NUM>). If the battery voltage is OK (above a preselected level) and there is no AC voltage in the body of water (<NUM>) the processor causes a green LED light to flash at a frequency fo (<NUM>).

If the battery voltage in the shock detector <NUM> is low (below a preselected level) and there is no AC voltage in the body of water (<NUM>) the processor causes the green LED light to flash at a frequency fx and an audible alarm to beep (<NUM>) where the frequency fx is different from the frequency fo. In this mode the operator is alerted to replace the battery in the shock detector. Thus the shock detector through the type of signals alerts the observer that that there is no water voltage but in one case it alerts the observer that the battery in the shock detector should be replaced even though no AC voltage has been detected.

If the battery voltage in the shock detector is low (i.e. below a preselected level) (<NUM>) and there is AC voltage in the body of water the processor causes the red LED light to flash and an audible alarm to beep (<NUM>) thus alerting the person to the hazardous condition as well as the fact the battery is low and needs to be replaced.

If the battery voltage in the shock detector is OK (i.e. above a preselected voltage) and there exists an AC voltage in the body of water (<NUM>) the processor in the shock detector provides more information such as the level of AC voltage gradient in the body of water. In this example the processor provides an audible alarm as well as visual alarm signals, which are based on difference in frequency of the flashing of the Red LED light.

The processor also has the ability to determine different levels of voltage gradients and alert an operator not only to the existence of a water voltage and a voltage gradient but the level or strength of the voltage gradient. As shown in the <FIG> flow chart, if the processor determines that the water voltage gradient is less than a preselected water voltage gradient V<NUM> (<NUM>) the processor causes the Red LED light to flash at a frequency f<NUM> and the audible alarm to beep (<NUM>).

If the processor determines the water voltage gradient is greater than V<NUM> but less than V<NUM> where V<NUM> and V<NUM> are preselected water voltage gradients (<NUM>) the processor causes the red LED to flash at a frequency f<NUM> and the audible alarm to beep (<NUM>) where the frequency f<NUM> is different from f<NUM>.

If the processor determines the water voltage gradient is greater than V<NUM> but less than V<NUM> where V<NUM> is a preselected water voltage gradient (<NUM>) the processor cause the red LED light to flash at a frequency f<NUM> and the audible alarm to beep (<NUM>) where the frequency f<NUM> is different from f<NUM> and f<NUM>.

In the event the processor determines the voltage gradient in the body of water is greater than V<NUM> (<NUM>) the processor then cause the red LED light to flash at a frequency f<NUM> and the audible alarm to beep (<NUM>) where the frequency f<NUM> is different from f<NUM>, f<NUM> and f<NUM>.

Thus, a feature of the invention is that the shock detector <NUM> provides unique open water informational signals responsive to a range of voltage conditions to alert an operator to the water voltage danger in the body of water but also the level of the voltage gradient in the body of water. The feature of being able to send different signals for different voltages in the body allows the shock detector to become a diagnostic tool for locating the cause of the electrical short in open water by using the shock detector to locate where the voltage gradient in the body of water is the highest. That is by displacement or movement of the shock detector in the body of water one can determine where the voltage gradient is highest by the change in frequency of the flashing red LED light. By searching in the area where the shock detector measures the highest voltage gradient one limits the search area thus enabling one to more quickly find the problem causing voltage leak into the body of water.

<FIG> shows an example of a water propelled shock detector <NUM>, which is identical to shock detector <NUM> except shock detector <NUM> includes means to move the shock detector from location to location in an open body of water. In this example shock detector <NUM> includes a first propeller <NUM> and a second propeller <NUM>, an internal power source such as a battery and a radio-control <NUM> as typically used in powered model boats. A remote control box <NUM> and a joy stick 95a allows the operator to move the shock detector <NUM> to different locations in the body of water through control of the rotation of propellers <NUM> and <NUM> while the red LED light <NUM>, the green LED light <NUM> and the beeper <NUM> provide information as to the presence of a voltage gradient but also the strength of the voltage gradient. Thus, the shock detector can be moved about in the body of open water without a person coming into contact with the body of water. Although, steering of the shock detector can be controlled by use of two propellers other methods of steering including a single pivoting propeller may be used without departing from the spirit and scope of the invention. Thus, with the use of a remote controller <NUM> an operator can remain on shore and away from contact with the water as the operator moves the shock detector <NUM> to various locations in the body of water, where the shock detector <NUM> can determine the existence as well as the strength of the voltage gradient. This feature of a remote controlled shock detector is not only useful in locating regions of high water voltage but is also useful in extending the range of the shock detector since the shock detector can be moved to a different location in the body of water to determine if there exists a harmful voltage gradient at a different location. That is, the shock detector typically has a useful range in determining a voltage gradient since the water voltage gradient decreases the further one is from the source of the electrical short. The decrease in water voltage gradient based on the distance from the electrical short is dependent on various factors including the salinity of the water. With the water propelled shock detector <NUM> one can move the shock detector about in the body of water to determine if harmful voltage gradients exist in other portion of the body of water. This feature is also useful in cases where the harmful water gradient is outside the normal range of the shock detector since one shock detector can be used to monitor harmful voltage gradients over an extended range by moving the shock detector from location to location. In other cases one may program the remote to direct the shock detector to automatically measure the voltage gradients at different locations in the body of water.

A further feature of shock detector <NUM> is a transmitter <NUM> that can send information on the harmful voltage gradient to a remote location. For example, the transmitter output may be in communication with an emergency squad, a power company or an entity that can respond if the shock detector determines a water voltage gradient has exceed a dangerous threshold that would injure or electrocute a person.

<FIG> shows the shock detector <NUM> may be moved about in open water through the coupling of the shock detector <NUM> to a conventional remote controlled model power boat <NUM>, which is attached to shock detector <NUM> by an electrically insulating cord <NUM>. In this example, the model boat <NUM> and its remote control can be used to tow the shock detector <NUM> to various open water positions on the body of water.

Claim 1:
An ungrounded battery powered shock detector comprising:
a housing (17a, 17b) ;
a first water electrode (<NUM>) for immersing in a body of water (<NUM>);
a second water electrode (<NUM>) for immersing in the body of water (<NUM>);
a third water electrode (<NUM>) for immersing in the body of water (<NUM>);
a processor (<NUM>) for measuring a voltage gradient between at least two of said water electrodes (<NUM>, <NUM>, <NUM>);
an alarm (<NUM>) for alerting a person to the existence of a harmful voltage gradient in the body of water (<NUM>) where the harmful voltage gradient is such that it could injure or electrocute a person,
wherein the detector (<NUM>) comprising the processor (<NUM>) is configured to
measure (<NUM>) a voltage of the battery (<NUM>) powering the detector and a voltage gradient in a body of water (<NUM>),
provide (<NUM>) a first signal if the battery voltage is low and there is no harmful voltage gradient in the body of water (<NUM>),
provide a second signal (<NUM>) if the battery voltage is low and there is a harmful voltage gradient in the body of water, and
provide a third signal if the battery voltage exceeds a safe level (<NUM>) with the harmful voltage gradient in the body of water with the first signal the second signal and the third signal different from each other.