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Old 03-02-2019, 11:16 AM   #1
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Default Multimeter mA and uA question

I pretty much don't ever have to use the mA or uA functions on my multimeter at work. I honestly can't even remember a time when I did. That being said I'm having a problem at home I'm not sure my meter is working correctly. I have an aquarium at home and recently had a bunch of fish die. I won't get into the details about how I thought to check for stray voltage and the tank but I did and my meter read 34 volts from the water to ground. Now its possible that this is induced voltage but in order to check to see if it's coming from a cracked piece of equipment like a pump or heater I decided to check for A, mA, and uA from water to ground. I didn't suspect it would be any amps otherwise my GF I would have popped the problem is when I turn my meter to AC mA I get a reading of 00.12 not connected to anything and uA I get a reading of 001.2 not connected to anything. Is this normal or should it read zero ?
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Old 03-02-2019, 11:21 AM   #2
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Cheaper digital meters are often off by a few mA.

The GFCI won't detect a line-neutral fault, which you might have. Try inserting a grounded wire into the water and see what happens. Check the voltage while doing it.
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Old 03-02-2019, 11:36 AM   #3
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I installed a titanium ground probe in the tank. Basically it's just a copper wire connected to a titanium probe that goes in the water and the opposite and hooks up to a ground. As soon as I put the ground probe in voltage drops to zero. If I pull it out of the water goes back up to 32 volts.
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Old 03-02-2019, 11:37 AM   #4
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Also this isn't a cheap meter, it's old but it's an expensive amprobe
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Old 03-02-2019, 12:57 PM   #5
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Quote:
Originally Posted by Eric23 View Post
Also this isn't a cheap meter, it's old but it's an expensive amprobe
The Amprobe question
1. Move the test leads to the proper jack.
2. A good ampmeter will have a zero function to kill off the extraneous readings.
3. Normaly the mA and uA jacks are fused inside the meter.
4. Without proper regular calibration meter readings are not worth much.


I don't know 'nothin' about gold fish.
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Old 03-02-2019, 02:18 PM   #6
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Your fish were swimming INSIDE a conductor. Under some circumstances, a fish tank can be isolated enough from ground that it functions like the plate of a capacitor. When that 'capacitor' discharges a voltage gradient can be established inside the tank. Oops.

Your crazy high voltage reading makes one worry that this low probability event may have occurred.

The typical fish tank is composed of dielectrics wrapping a conductor. ( the water is not pure )

One either figures out what component is pumping it with EMF or one bleeds off the EMF with a GEC. Because the power involved is a joke, the cheapest solution usually is to just ground the water. ( Install a chemically un-reactive electrode and connect it to the grounding pin. )

Bizarrely high voltage readings (45 volts) have also been witnessed in plain vanilla hot tubs -- the ones that come as a factory assembly. Again you have a dielectric totally surrounding a conductor. ( Human sweat creates salted water.)

[ All fish are extremely vulnerable to disease and water borne toxins. So always keep your eye on that angle. ]
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Old 03-02-2019, 02:24 PM   #7
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If you have 34 volts from water to ground, did you try and unplug one piece of equipment at a time?

Amps from water to ground should only be whatever the resistance of the meter is at that setting. I would guess the internal resistance of the meter is going to be different at different settings?

You might not want this thread to reach any code making panels. Next you’ll have to put a swimming hazard to fish sticker on your tank in the next code cycle.
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Old 03-02-2019, 02:26 PM   #8
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Quote:
Originally Posted by telsa View Post
Your fish were swimming INSIDE a conductor. Under some circumstances, a fish tank can be isolated enough from ground that it functions like the plate of a capacitor. When that 'capacitor' discharges a voltage gradient can be established inside the tank. Oops.

Your crazy high voltage reading makes one worry that this low probability event may have occurred.

The typical fish tank is composed of dielectrics wrapping a conductor. ( the water is not pure )

One either figures out what component is pumping it with EMF or one bleeds off the EMF with a GEC. Because the power involved is a joke, the cheapest solution usually is to just ground the water. ( Install a chemically un-reactive electrode and connect it to the grounding pin. )

Bizarrely high voltage readings (45 volts) have also been witnessed in plain vanilla hot tubs -- the ones that come as a factory assembly. Again you have a dielectric totally surrounding a conductor. ( Human sweat creates salted water.)

[ All fish are extremely vulnerable to disease and water borne toxins. So always keep your eye on that angle. ]
It may also be a reaction from the earths magnetic field and the body of water. He should try spinning the fish tank 90 degrees.
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Old 03-03-2019, 03:03 AM   #9
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Even with voltage in the water, unless your fish can reach something grounded, they won't get shocked. Kinda like a bird on a high voltage power line.
Your meter shouldn't read any amps when there's no amps flowing through it. It may read small voltages because of a potential difference between the leads. Is the meter shielded? (foil on inside of the case.)
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Old 03-03-2019, 05:10 AM   #10
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Even with voltage in the water, unless your fish can reach something grounded, they won't get shocked. Kinda like a bird on a high voltage power line.
Your meter shouldn't read any amps when there's no amps flowing through it. It may read small voltages because of a potential difference between the leads. Is the meter shielded? (foil on inside of the case.)
It's the voltage gradient. No current may he going to ground, but instead from L to N through the water. There will be different voltages at different points in the water. If you put a conductor (fish) between two points along the gradient, current will flow.
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Old 03-03-2019, 05:24 AM   #11
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You guys are all way off base. The problem is not voltage, the fish died due to global warming and climate change. Probably was some sea level changes in the tank as well.
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Old 03-03-2019, 05:49 AM   #12
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Quote:
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It's the voltage gradient. No current may he going to ground, but instead from L to N through the water. There will be different voltages at different points in the water. If you put a conductor (fish) between two points along the gradient, current will flow.
I think if you suspend that titanium ground rod in the water at one end of the tank, then probe around in the tank with one lead of your meter (other lead grounded), you'll find the voltage dropping from 32V to 0V across the water in a straight line between the titanium rod and the guilty device.

Maybe the fish would learn to avoid that like dogs learn the invisible fence.

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Old 03-03-2019, 05:50 AM   #13
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It's the voltage gradient. No current may he going to ground, but instead from L to N through the water. There will be different voltages at different points in the water. If you put a conductor (fish) between two points along the gradient, current will flow.
Seriously? I thought that only worked for cows, or high voltage, as in "step voltage". If there's a hot on one side of the tank, and the neutral on the other, then the tank is wired wrong. Needs an EGC.
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Old 03-03-2019, 05:54 AM   #14
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Seriously? I thought that only worked for cows, or high voltage, as in "step voltage". If there's a hot on one side of the tank, and the neutral on the other, then the tank is wired wrong. Needs an EGC.
No it's exactly like the step voltage on the ground. I have a very hard time visualizing it.

Think about the fact that current takes ALL PATHS. If you put an anode and a cathode in water, current will flow through the water from one to the other. But it isn't all in a laser line from point A to point B. Why wouldn't current take a path that is slightly bent? Well, it does, it takes all paths.
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Old 03-03-2019, 05:56 AM   #15
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No it's exactly like the step voltage on the ground. I have a very hard time visualizing it.

Think about the fact that current takes ALL PATHS. If you put an anode and a cathode in water, current will flow through the water from one to the other. But it isn't all in a laser line from point A to point B. Why wouldn't current take a path that is slightly bent? Well, it does, it takes all paths.
BTW this is a problem for humans as well as fish

https://www.electricshockdrowning.org/esd--faq.html
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Old 03-03-2019, 11:41 AM   #16
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On some meters, on AC volts with one or two probes floating, you can see various extraneous readings. Once you touch a "solid" (known) voltage the reading should stabilize.
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Old 03-03-2019, 12:13 PM   #17
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Drive 2 ground rods into the gravel at the bottom of the tank. Bring the ground wire through the hood with a Kenny clamp.
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Old 03-03-2019, 12:19 PM   #18
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Drive 2 ground rods into the gravel at the bottom of the tank. Bring the ground wire through the hood with a Kenny clamp.
What's a Kenny clamp?
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Old 03-03-2019, 03:26 PM   #19
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No it's exactly like the step voltage on the ground. I have a very hard time visualizing it.

Think about the fact that current takes ALL PATHS. If you put an anode and a cathode in water, current will flow through the water from one to the other. But it isn't all in a laser line from point A to point B. Why wouldn't current take a path that is slightly bent? Well, it does, it takes all paths.
Are we talking AC, or DC here? What would be the source voltage in an aquarium? Pump, heater? Those would be singe point sources. Where would the ground potential come from? And, current takes the path of least resistance.
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Old 03-03-2019, 03:46 PM   #20
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'Kenny clamp' is a joke.
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