water conductive sensor

[kielex]

can i have a simple conductive sensor that detect TDS total dissolve solids

 

[Mikebits]

Huh??? You need more details.

 

[jpanhalt]

Do all solids, including ones such as dextran, affect conductivity the same as sodium chloride? John

 

[Hero999]

I wouldn't think so, sugar certainly won't be as conductive as something like NaCl. There are lots of ways of measuring this kind of thing, it depends on what dissolved chemical(s)s you're looking for.

 

[jpanhalt]

Actually, that was my point. The term "dissolved solids" may have a specific, narrow meaning according to some regulation or it may have the meaning implied by the words. If it is the former, and that regulation requires conductivity testing, then that is what is needed.

On the other hand, for example, if the need is for water that will be used in trace analyses where dissolved solids include any soluble substance, then the methods for analysis are considerably more complex.

John

 

[BeeBop]

If it is for a fish tank or hydroponic nutrient measure, then typically, sodium chloride is used as a reference.

If used for trace analysis, then it must be calibrated accordingly.

This cannot be done with a DC current, as the solution will ionize... you will need to use AC.

 

[duffy]

Maybe kielex could try using a capacitance meter that reads Q (or D) and use a couple of closely-spaced insulated plates in the water - ?

 

[Speakerguy]

He needs a water conductivity meter that reads in microSeimens/centimeter. This gets converted to a TDS number in the microcontroller. The correlation between uS/cm and TDS in ppm depends on the standard you calibrate against, because the different standards have slightly different ion mobilities and therefore conductivities. You need to calibrate the system with your chosen calibration standard so that the conductivity number gets translated to the correct TDS number. Standard calibration solutions are available in NaCl, KCl, and '442'. You probably want NaCl or KCl for most applications.

 

[BeeBop]

Maybe kielex could try using a capacitance meter that reads Q (or D) and use a couple of closely-spaced insulated plates in the water - ?

But is is NOT water; it is an ionic solution. (Isn't the cap meter DC?)

The plates should be made of gold plated material, or something which will resist corrosion. A small audio plug will work for this.

 

[Mike_2545]

What you seek is a Brix meter.

 

[duffy]

(Isn't the cap meter DC?)

No, a cap meter is AC. May have an offset for polarized caps, but it generates and reads sine waves.

The conductivity of the solution would translate to a resistive power loss which would decrease the "Q" (or increase the "D" - dissipation) of the capacitance between the plates. Changes to the solution might affect the permittivity in a useful way, which you could then read as an increase or decrease to the capacitance of the fixed-size, fixed-distance plates.

MIGHT work, if the dissolved solids are known and very limited in scope.

 

[kielex]

actually i will use this meter for hydroponic nutrient-water testing and coupled it to a microcontrolller. Is capacitance meter the same with a moisture sensor used in soils?

 

[BeeBop]

actually i will use this meter for hydroponic nutrient-water testing and coupled it to a microcontrolller. Is capacitance meter the same with a moisture sensor used in soils?

No, they aren't the same. An electro-conductivity meter is what you want, as speakerguy79 pointed out above.

How much experience do you have with electronics? Have you ever worked with op amps?

What kinds of tools do you have at your disposal?

 

[Mike_2545]

Forget electronics, the real question is how much hydroponic experience kielex has.
The best control system in the world will not help a non-green thumb.

Most commercially available water based nutrient solutions have mixing directions on the package. If you are going with a more home brew fertilizer you can get a fertilizer meter to test the strength.

 

[duffy]

Forget electronics and hydroponics, the real question is how decent the weed is.

A soil tester is either conductive or galvanic (I have a nifty batteryless unit).

For what you're doing, you might just start out with a simply multimeter and a couple of fixed-distance plates. Measure the resistance with different solutions and see what you get with that before moving on to something more complex.

 

[BeeBop]

Forget electronics and hydroponics, the real question is how decent the weed is.

A soil tester is either conductive or galvanic (I have a nifty batteryless unit).

For what you're doing, you might just start out with a simply multimeter and a couple of fixed-distance plates. Measure the resistance with different solutions and see what you get with that before moving on to something more complex.

Why don't you give this a try, before recommending it? Not the weed, the meter!

You will get a reading for less than a second, then the meter will rise to infinity.

 

[in10ceguy]

How about conductivity monitor with carbon tips. I dont think carbon corrodes.

**broken link removed**