Skip navigation

community

Up to Discussions in Electronics Test and Measurement | Electronic Test Equipment
652 Views 3 Replies Latest reply: Nov 25, 2011 10:23 PM by meisteros RSS
nigelhales Level 1
nigelhales
3
Currently Being Moderated

Oct 22, 2011 5:00 AM

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.

Attributes
Tags: circuit, measurement
  • DAB Level 8
    DAB
    Currently Being Moderated
    1. Oct 22, 2011 2:46 PM (in response to nigelhales)
    Re: Conductivity Circuit

    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

  • nigelhales Level 1
    nigelhales
    Currently Being Moderated
    2. Oct 24, 2011 5:13 AM (in response to DAB)
    Re: Conductivity Circuit

    Dear DAB, thanks for the conductivity circuit information, I'll check

    it out, regards, Nigel.

  • meisteros Level 1
    meisteros
    Currently Being Moderated
    3. Nov 25, 2011 10:23 PM (in response to nigelhales)
    Re: Conductivity Circuit

    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

Related Content


Related Products
Discussions
  • Retrieving data ...

Bookmarked By (0)

Legend

  • Correct Answers - 50 points
  • Helpful Answers - 25 points