detect current direction in water

a bowl is filled with tap water .electric current is made to flow due to electrodes attached to rim of bowl(opposite sides of bowl)
i have 2 sense pins inserted into the water between the electrodes .
how can i convert this analog signal(vd across sense pins) to a digital signal to detect direction of current through water and use the signal in a logic circuit?
the 2 sense pins are fixed in water whereas polarity of supply electrodes is varying with time
electrode vd is max 5v min -5V. ammeter reads 700 microamps current flowing through water
all i need to know is if vd across sense pins is + or -ve
+ve or 0 vd = high output
-ve vd = low otput

Why do you need a sensor in the water? Just measure the voltage applied to the electrodes.

I would use a voltage comparator powered by the same +-5 volt power supplies.

.

Grumpy_Mike:
Why do you need a sensor in the water? Just measure the voltage applied to the electrodes.

sensor pin 1 is attached to tail of my cat. sensor pin 2 is attached to tail of my dog.
when both lick water who licks which region of the water in the bowl?

How will you know when the cat and dog are drinking?

LarryD:
I would use a voltage comparator powered by the same ±5 volt power supplies.

.

where can i get one?

jremington:
How will you know when the cat and dog are drinking?

a horizontally rotating ir sensor just above water surface detects number of tongues
and it turns out i have only 2 pets

Seems a camera surreptitiously placed above the bowl would answer your question in short order.

ChrisTenone:
Seems a camera surreptitiously placed above the bowl would answer your question in short order.

webcam will exceed my project budget

This is a "thought experiment", right? A puzzle, a test? You have no intention of attaching electrodes to the shaved tails of your pets, real or imaginary?

You would need to place the bowl on a large rubber mat, so that the voltage at the tongue reaches the tail and does not leak away to earth through their paws. Worse still, if the pets walk over nylon carpet to reach the bowl, they might have thousands of volts of static on their bodies, dwarfing the fraction of a volt you are trying to measure.

Instead of a web cam, use whatever is stuck onto your eye, in "your photo".

PaulRB:
This is a "thought experiment", right? A puzzle, a test? You have no intention of attaching electrodes to the tails of your pets, real or imaginary?

You would need to place the bowl on a large rubber mat, so that the voltage at the tongue reaches the tail and does not leak away to earth through their paws.

the floor is carpeted. my pets are locked inside the room and free to move

Do we need to call PETA on you? :wink:

Suggest you use the common LM339.
Should be available in most countries.

Google for circuits.
Look at different data sheet for circuits.
Maybe a zero crossing detection cct. would work.
.

Typical data sheet.

.

SumitAich:
the floor is carpeted. my pets are locked inside the room and free to move

Free to move except for the electrodes attached to their bare tails?

There is no way this is going to work. The tongue voltage vs tail voltage idea is just silly! Leave the poor animals alone!

Can't imagine most cats drinking from a bowl with a scanning sensor whirring away, unless the cat is desperately thirsty, in which case we will be calling the RSPCA.

Probably a troll.

2 Ultrasound sensors, 1 at cat height, 1 at dog height.

LarryD:
Suggest you use the common LM339.
Should be available in most countries.

Google for circuits.
Look at different data sheet for circuits.
Maybe a zero crossing detection cct. would work.
.

is it sensitive enough to detect voltage drop of order 10mV

SumitAich:
is it sensitive enough to detect voltage drop of order 10mV

Yes

Edit:
Voltage differences.

.