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Topic: Conductivity measuring  (Read 820 times) previous topic - next topic

Dragonsired1

Sep 10, 2017, 06:52 pm Last Edit: Sep 10, 2017, 07:51 pm by Dragonsired1
Hello,

I tried to find an easy and reliable way of measuring conductivity of water samples but failed by looking on very complicated schematics. I don't want to use voltage divider as it makes more problems than usefull data. Please can you provide me with more information about this topic?

Thanks.

Paul_KD7HB

Hello,

I tried to find an easy and reliable way of measuring conductivity of water samples but failed by looking on very complicated schematics. I don't want to use voltage divider as it makes more problems than usefull data. Please can you provide me with more information about this topic?

Thanks.
Conductivity is the reciprocal or resistivity.

Out old circuit board washer measured the resistivity of the water and stopped washing at 1 meg ohm. The new board washer stops washing when the wash water measures 1 microSiemen. Same exact measurement, just different values.

What is your problem with voltage dividers? Somewhere you have to have a range of voltages that an Arduino can measure.

Paul

Dragonsired1

#2
Sep 11, 2017, 10:02 am Last Edit: Sep 11, 2017, 10:39 am by Dragonsired1
Quote
What is your problem with voltage dividers?
The problem is, that there's too much voltage across probe and electrolysis occurs. First two readings are OK but after some time results vary more than 100%. I found somewhat easy solution with 555 here:
555-conductivity-meter
But the problem is that Arduino would have to then measure frequency which is tricky.
I though about using frequency to voltage circuit or try to make steady current source for let say 25uA and use simple ohms law to calculate voltage with given resistance. What's better idea?

stowite

But the problem is that Arduino would have to then measure frequency which is tricky.
To my mind just the opposite of tricky. There are many many examples of using Arduino to measure frequency.

Wawa

There have been TDS (total dissolved solids) threads on this site.
This one (post#40) might start you off.
Leo..

Delta_G

The problem is, that there's too much voltage across probe and electrolysis occurs.
Yeah, don't use DC. 
If at first you don't succeed, up - home - sudo - enter.

Johan_Ha

Quote
The problem is, that there's too much voltage across probe and electrolysis occurs.
Even if the voltage is there only for a millisecond?
____________________
- One day my stepper motor driver works like a charm. No task is too big for it and I can do anything with it. Next day it refuses to work and even the tiniest motor blows its fuse. What's wrong with it?
- It's bipolar.

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