Need help with a circuit


Joined Jul 17, 2007
I don't see a screen capture image of your Multisim schematic; only one that looks like it came from a website somewhere.

You should bring up the schematic in Multisim, do a screen capture by pressing Ctrl+PrintScreen, and then start MS Paint and paste the image into Paint.
Then save the image in .png (portable network graphics) format, and upload it to the forum.

.png format is preferred, as the format is very compact, needs no other software than a browser to view, and is not "lossy" like .jpg files are.


Joined Dec 20, 2007
Multisim does not make an oscillator run unless something "kicks" it to run.
Multisim does not know that the liquid is supposed to conduct a little or a lot.

The circuit will work if you build it and use lots of salt in the liquid to make it conduct.


Joined Jan 28, 2005
This circuit does not work on MultiSIM Please tell me what is the problem
If you happen to know what the conductivity of the liquid you are sensing is then you might try substituting an equivalent value of resistance to see how your sensing circuit would react.



Joined Jul 1, 2008
You didn't say what your liquid is but just about all water (except for distilled) will easily conduct enough to forward bias the transistors in your circuit. It's not the water that conducts, it's the minerals that's suspended in it. It looks like your building a beep-beep-... circuit.