electricity detection in water

[jujutx]

I am looking for a way to detect minute traces of electricity in water. Does anyone know of any COTS product that already does this. Or any discussion on good idea on how to create one? Thanks in advance.

 

[leitmotif]

A better description of what you want to measure and why you want or need to do it would sure help - example - what is minute - the potential between sodium and chloride ions in salt water?

Dan Bentler

 

[Lancie1]

minute (mi-noot') definition: extremely small in size, infinitesimal, minuscule.

 

[jujutx]

I build equipment for people who handle and research exotic animals such as zoos aquariums, sanctaries. I was asked by a researcher it there was a way to detect the presence of electrical currents in water. The research is to understand species that use electrical detection and production. So minute means very small amp detection. Could be either salt or fresh water.

 

[Lancie1]

For any electrical current to exist, there must be a transfer (flow) of electrons from one place to another, through some conductive medium (water in your case). To measure any current, your measuring device must have two sensor points, the first connected to the orignation point, and the second connected to the receiving point.

For example, if the Originator is an electri eel, and the Receiver is some other marine species, to measure any electrical current flowing through the water between the two would require some type of connection to each organism. I suppose you could put each life species in some type of "confining cage" with conductive brushes that pick up any currents in the immediate area.

 

[jujutx]

I am familar with how voltage is captured. I understand how electricity works. What I am looking for is a sensor or creation of a sensor that can be placed in the water that will detect it. This is not to cage an animal but to study and understand how they work. Electric eels create large voltage, however sharks and cetacea detect it. What is not understood is the levels the detect or if they also produce. I just would like to know if there are already sensors out there that have been produced to work in water. If not does anyone know of a mfg that produces something close. The outcome is understanding how these animals do what they do. Sharks attack even in zero visibility, how do the get attracted outside of blood. They are attracked and frenzied by electrical current. They are also repealed by it. So. Now the study is do they produce it as well. The other studies just input currents, now detection is necessary. This could save lives down the road. Also being able to probe areas for weld a.d catfish that could kill is also important.

 

[danw]

Conductivity probes apply a known potential (excitation)and look for the resulting current through the resistance between the electrodes. Stray electrical currents are conductivity's nightmare.

I've seen conductivity probes work fine in a beaker full of solution from a vessel, but when the conductivity probe is inserted into a vessel, the conductivity value drives offscale because of currents in the vessel.

The problem is that an aquarium's water conductivity is likely to vary minute to minute due to its inhabitants who defecate, eat the food tossed into the water, breathe, water conditioning, whatnot.

Perhaps a baseline could be achieved by drawing sample stream that is electrically isolated from the main body of water, dropping it into a beaker which constantly overflows to a drain and measuring its conductivity.

Comparing the baseline conductivity to an in-situ conductivity probe might reveal electrical currents. Stuff's COTS.

 

[harryting]

from wikipedia:

Most fish possess highly developed sense organs. Nearly all daylight fish have color vision that is at least as good as a human's. Many fish also have chemoreceptors that are responsible for extraordinary senses of taste and smell. Although they have ears, many fish may not hear very well. Most fish have sensitive receptors that form the lateral line system, which detects gentle currents and vibrations, and senses the motion of nearby fish and prey.[19] Some fish, such as catfish and sharks, have organs that detect weak electric currents on the order of millivolt.[20] Other fish, like the South American electric fishes Gymnotiformes, can produce weak electric currents, which they use in navigation and social communication.

 

[Lancie1]

I am familar with how voltage is captured. I understand how electricity works. What I am looking for is a sensor or creation of a sensor that can be placed in the water that will detect it. This is not to cage an animal but to study and understand how they work.

Apparently your knowledge of electricity may have a few weak spots. You cannot place a sensor in the water that will detect current, unless you have TWO points of differing potential to measure. My point was, for the purposes of developing such a detection system, you COULD put animals in a type of cage that would provide these TWO necessary points to measure. Just placing a sensor in water only gives you ONE reference point. Current has to flow between TWO points. Now you might use TWO separate electrodes, located some distance apart, and measure the stray electrical current between the two sensors. To do that, practically ANY type of metallic plate would work, with an insulated wire from each pad connected back to a miliampere meter. It would probably be best to use some metal that is resistant to seawater corrosion, such as stainless steel, nickel, or platinum.

EDIT: Even though a system to measure currents in water is fairly simple, the difficult part will be determining the source of any current measured. I would guess that if the sensor electrods are placed 100 feet apart, that there will be stray and varying currents detected. These could be from life in the water, or from temperature differences, or from different pH levels, or who knows what. That is where it may be necessary to do a controlled experiment in a pool of water with known temperature, pH, metallic content, and other factors, and with the living organisms in cages set at a known distance apart.

Otherwise, your unknown factors will overpower any detection of stray current in a wild body of water.

 

[bce123]

I am looking for a way to detect minute traces of electricity in water

Im thinking voltage (output from fish)? ohms(water)? if you have E and R? I=E/R

 

[DamianInRochester]

Hi guys,
This link explains it better.

http://en.wikipedia.org/wiki/Electroreception

More so what your looking to do is measure an electric field.

You might not be able to emply the same technique in brine as you would fresh water.

From Wikipedia:

"Active electroreception relies upon tuberous electroreceptors which are sensitive to high frequency (20-20,000 Hz) stimuli. These receptors have a loose plug of epithelial cells which capacitively couples the sensory receptor cells to the external environment. Passive electroreception however, relies upon ampullary receptors which are sensitive to low frequency stimuli (below 50 Hz). These receptors have a jelly-filled canal leading from the sensory receptors to the skin surface. Mormyrid electric fish from Africa use tuberous receptors known as Knollenorgans to sense electric communication signals"

Your best bet is to design your own sensor by trying to mimic the way nature already does it.

 

[TConnolly]

This is a total WAG, but it may be possible to use hall effect sensors, but they would probably have to be $pecialty $ensor$.

Sufficiently sensitive Hall effect sensors would require no exposed contacts in the water or contact with the organisms.

The hall effect is a voltage that develops in a current carrying conductor that is perpendicular to a current flowing in an adjacent conductor. Typically a known fixed current is applied to an insulated conducting plate through opposite sides, and the plate is placed in or near another electrical conductor. Then the perpendicular voltage is measured across the adjacent edges of the plate. That voltage will be proportional to the magnitude of the current flowing in the conductor being measured.


I'm not entirely sure it would work in water however and bio electric current is so small that the hall effect sensor would have to be exceptionally sensitive. An array of sensors would be required and you would have to do significant digital processing to determine which direction the current was flowing. The sensors would have to be so sensitive tha the test area would have to be completely isolated from external magnetic and electrical fields, and probably establish a baseline to allow you to subtract out Earth's magnetic field.

 

[Lancie1]

Possibly some type of magnetometer could be used to measure animal-generated electric fields. However, the environmental noise in a typical body of water is going to be difficult to filter out, due to the low levels of animal electromagnetic field transmission (very low levels approximately 1 X 10−7 Teslas).

A superconducting quantum interference device (SQUID) is a type of magnetometer that can measure very weak fields, based on superconducting loops containing Jopsephson junctions. SQUIDs can measure electric fields down to about 5 x 10−18 Teslas. The next question is whether an underwater SQUID sensor loop is available, and if it can be tuned to the frequency ranges that animals generate.

 

[bce123]

just a related tid bit:
http://www.cornell.edu/video/?videoID=874

 

[leitmotif]

Possibly some type of magnetometer could be used to measure animal-generated electric fields. However, the environmental noise in a typical body of water is going to be difficult to filter out, due to the low levels of animal electromagnetic field transmission (very low levels approximately 1 X 10−7 Teslas).

A superconducting quantum interference device (SQUID) is a type of magnetometer that can measure very weak fields, based on superconducting loops containing Jopsephson junctions. SQUIDs can measure electric fields down to about 5 x 10−18 Teslas. The next question is whether an underwater SQUID sensor loop is available, and if it can be tuned to the frequency ranges that animals generate.

Lancie
Have you been studying again?

Dan Bentler