Conductivity Circuit

Wondering if anyone can help.

Need to design conductivity circuit to interface with standard sensor to measure in NaCl solution.

Sensor has PT100 temperature sensor (for compensation) and plate electrodes need to drive with AC stop liquid polarisation current flow proportional to conductivity mS.

Will interface to PIC for logging.

Can use AC bridge measurement. Had though use LVDT drive circuit AD do one expensive.

Any thoughts.

0 DAB over 14 years ago

There was a blog on a salt detector on Hackaday a few month ago. It used an RC circuit to measure the resistance between clean water and salt baring water. As I recall, the circuit used an LM324 operational amplifier with various levels of gain. Once you calibrate it to zero out with pure water, you can then measure various levels of salt in the water by the RC time constant change.

Hope this helps.
DAB
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0 Former Member over 14 years ago in reply to DAB

Dear DAB, thanks for the conductivity circuit information, I'll check
it out, regards, Nigel.
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0 Former Member over 14 years ago

I am buidling a temperature measurment system, using Pt100. My problem is that I need a 1mA curent source. I found a application note using mcp602. Instead of it I'm using lm358, but I dont know how to make the supply for the op. amps. I tried to simulate the circut with microsim. The results were as I wanted to be. The main problem is that I tried to supply the op. amps with one, the same source and the courent source doesn't work properly. How I supose to make the suply for the op. amps.Link to schem.:
http://www.wrzuc.net.pl/?v=zrodloprad.jpg
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0 Former Member over 10 years ago
hello sir need one help......
need a conductivity sensor circuit for dialysis machine please help me..

Requirements for conductivity sensor:
Conductivity Range- 10 to 16 mS/cm
Accuracy-0.1%
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0 michaelkellett over 10 years ago in reply to Former Member

Your link doesn't work. (Server not found error.)

If you can fix it or better still post the picture directly onto E14 I'll take a look.

MK
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