DIY Conductivity Probe/Meter

[Randy Holmes-Farley]

I believe it is graphite.

[BeanAnimal]

Originally Posted by oemtds

Yes Randy your "commercial" meter has selectable ranges(aka changes resistor values) but have you tested see if it will read DI water and then 50000Micro/s dead on? If it does great. Mine is not a commercial product nor it costs $200.
Anyways i showed what i have made . So far i see sheac12, cyrusthevirus constantly asking BeanAnimal to show his project but for obvious reasons its on hold.
Instead he 's showing whats inside his mp3 player hahaha.
Anyways you guys are too much fun.

Here is the problem OEM, Your just trying to leverage a fish forum to drum up business for the products you SELL. You keep avoiding the questions and acting like your one of us, you are not. The fact that I have not posted a working project has no relevance to YOUR actions. I don't (and never have) had anything for sale, you do and can not post a project or plans because I don't have one to post yet. Are you going to post your schematics, bill of materials and construction plans or do I need to send you money via PayPal first?

You act like a planted aquarium hobbyist, and a hydroponics hobbyist, and anything else that will help garner intersest in your "non commerical" kits. You get banned and then move on to the next forum. What is funny is that you think playing these games somehow makes you different than any other spammer who comes here looking to solicit sales for his or her products.

[dainiusiva]

Originally Posted by BeanAnimal

Here is the problem OEM, Your just trying to leverage a fish forum to drum up business for the products you SELL. You keep avoiding the questions and acting like your one of us, you are not. The fact that I have not posted a working project has no relevance to YOUR actions. I don't (and never have) had anything for sale, you do and can not post a project or plans because I don't have one to post yet. Are you going to post your schematics, bill of materials and construction plans or do I need to send you money via PayPal first?

You act like a planted aquarium hobbyist, and a hydroponics hobbyist, and anything else that will help garner intersest in your "non commerical" kits. You get banned and then move on to the next forum. What is funny is that you think playing these games somehow makes you different than any other spammer who comes here looking to solicit sales for his or her products.

well said

[oemtds]

Excuse me but this thread is about conductivity meter isnt it?and i share my thoughts just like anyone else,no one is pushing you to buy anything. its ok i forgive you BeanAnimal.

[oemtds]

Originally Posted by cyrusthevirus

I worked with the one located here, http://www.octiva.net/projects/ppm/ but it was hard to understand. I tried to reach out to the person, but never heard back from them. I also wanted to include the - 12 VAC conversion in the board so I only needed to suppy 12 VAC instead of + and - 12 VAC.

Unfortunately I do not have a scope.

The probes I purchased from China. The range should work for saltwater, but I will not know until I get a working prototype.

PM me on the PCB if you are interested. I think I have 6 or so extra ones.

cyrusthevirus there is an easier way to generate -12vdc with far less components , i will email you the schematics.

[oemtds]

Dont be hostile BeanAnimal just because someone smarter than you talks about real issues instead of promoting HM products . Because of you i may get banned (no sweat) but you are here to keep folks in your limited narrow circle of products made in Korea.

[oemtds]

Originally Posted by dainiusiva

well said

Correction

I am avoiding YOU because youre the only one that acts like an umm how should i say this (OEMTDS fan) that for some reason i dont know what it is ,perhaps youre scared of competition? or lack of knowledge about how conductivity circuitry works , i dont know..whatever it might be ,you try to divert from the real subject and poison the room.

[liquidarts]

Cyrus,

Any chance of you releasing the eagle and BOM files to the salinity reader?

[cyrusthevirus]

Originally Posted by liquidarts

Cyrus,

Any chance of you releasing the eagle and BOM files to the salinity reader?

I can not believe I actually found these. It took a lot of searching:

BTW I have some extra PCBs of the circuit if you are interested.

BOD
R1 1K
R2 1K
R3 56K
R4 33K
R5 100K
R6 1K
R7 6.8K
R8 22K
R9 1K
R10 220K
R11 220K
R12 220K
R13 100K
R14 100K
R15 82K

U1 TL074
V1 100K
V2 2K
V3 22K

C1 .015uF
C2 .015uF
C3 .22uF
C4 3300uF
C5 3300uF
C8 1uF
C6 3300uF
C7 3300uF
C9 1uF
C10 1uF
C11 1uF

D1 1n4733A
D2 1n4733A
D3A 1N4148DO35-10
D3B 1N4148DO35-10
D3C 1N4148DO35-10
D3D 1N4148DO35-10

CR1 1N4004
CR2 1N4004
CR3 1N4004
CR4 1N4004
CR5 1N4004
CR6 1N4004

IC1 LM79L12
IC2 LM78L12

X1 BNC PCB connector
X2 Phoenix CONN TERM BLOCK 4POS 5.08MM PCB
X3 DUAL LEAF DIP SOCKETS 14-pins

12VAC 500MA

[BeanAnimal]

I think the bigger question is with regard to how the project is working.

[taijiguy]

Found this topic from a Google search and thought I'd revive the thread as I'm in the process of building a similar automated system. I'm wondering about the status of this project, and about the probes. I also thought I would add for comment that I've seen elsewhere the use of titanium for the probes. Any thoughts on that?

[POPSIE]

We're working on a portable water purifier with a built in tester and one of the parameter that our tester should be able to measure is the salinity of water... can you share to us the current status of your circuit? if you could share to us sir... we're also trying to build a ORP tester if there is anything you could share to us we would be very thankful.... poviclang@yahoo.com

[cyrusthevirus]

Every couple of years I get some interest in this circuit so I wanted to provide the current status. Unfortunately the status has not changed. I have EC probes but I am not sure if they will work for the range required. If anyone wants to try to take this project on, PM me. I can send over the prototypes I created. I just don't have the equipment or the time.

[lab14lab]

Hi

I am designing a conductivity probe which consists of coaxial cylindrical electrodes in order to measure the electrical conductivity of electrolyte solutions. I can't seem to find any literature on how to go about the design and how these type of sensors work. Do you guys recommend any textbooks or literature that explains this really well as I don't have an electrical background.

Many Thanks

[surajpadhy]

I used the schematic available at octiva.com but it didn't worked for me. there was no change at output when the water or a connected resistance value was changed.

Please suggest any corrections in that schematic or any other working circuit.

Thanks..

[fustilarian]

Just skimmed this thread and saw no mention of this company so i figured i'd chime in with it. www.atlas-scientific.com sells all sorts of useful diy probes and circuit boards to read the probes and output i2c or UART. Not exactly cyrusthevirus level DIY but for all the wannabe EE's out there (like me) it should suffice. HTH

[ciuffoly]

Originally Posted by cyrusthevirus

Sorry for the delay, I was out of town. Here is the diagram for my circuit. It should work. I have had it reviewed by a lot of people. PM me if you are interested, I have some extra PCBs of it.



On another note I received all of my probes. I need to setup my standardized solutions so I can begin testing.

Could you share the pcb layout ?

[pringlescan]

Hello All,

I was wondering on how you were making out with your DIY circuit. I was unable to find a completely implemented and tested EC probe and circuit in the Arduino community so I opted to go with this:

• http://www.atlas-scientific.com/prod...ts/ezo_ec.html
• http://www.aliexpress.com/snapshot/6...64777608620548

The Atlas Scientific stuff is expensive but easy to interface with and accurate. It expects you to know your probes cell constant (K) value. This is apparently related to the distance between conductors and the surface area exposed. I have yet to see a cheap probe specify this value. I have reached out to several vendors and am awaiting a response.

I have both 111800us/cm and 12880us/cm conductivity solution to perform a two-point (high/low) calibration. After calibration, I get the correct EC values for both solutions despite them being well outside the specifications of my probe.

The problem I ran into however was that the specific gravity does not match my refractometer even when the EC value is accurate.

This is my refractometer, I have calibrated it using distilled water according to the manufacturers instructions:
http://www.amazon.com/Refractometer-...=refractometer

I was under the assumption that using the EC value you could derive the specific gravity, salinity, and TDS.

Apparently, it may not be that simple. As even with the correct EC value, you can still have an incorrect specific gravity/salinity with this commercial/scientific/well-tested circuit.

I'm posting here because I'm interested in not using a $50 circuit in my open source aquarium project... and also because I have yet to get this to work correctly.

I also want to caution interested parties that this in theory is trivial, but in practice can be complicated. Lights and pumps are notorious for leaking electrical noise (and with faulty equipment current!). Sharing a common ground between your aquarium equipment and your microcontroller can skew results.

It's also worth noting that you'll need to have your EC probe off for a second or two before your PH probe (and possibly other probes) take measurements.

[BeanAnimal]

I am not quite sure I would agree regarding the quality if the Atlas Scientific stuff...

At one point they claimed that their PH circuit did not need calibration... uhh yeah, sure if you use their PH probe and assume that they are all pre-tested to fit the hard coded slope, sensitivity and offset in the circuit... nonsense. I purchased one for giggles and find it to be useless.

Anyway...

[dartier]

Ugh, I just order the Atlas EC kit a few days ago. It is certainly not cheap, I just hope it works as expected.

I already have their ORP and Oxygen. The Oxygen has worked fine, buy the ORP has been very sensitive to other electrical interference. I attribute it to the EMI thrown off by my PWM lines driving my Meanwell boards. The readings would become crazy as soon as my LEDs would kick on for the day. To help counter this I changed my PWM lines to using shielded CAT-5 for the longish run to the lights. This helped somewhat. My Oxygen probe became useable, the ORP not so much. So for this order I added one of their carrier boards so that I can try to isolate the probe circuits into a remote shielded box near the tank.

The Atlas Scientific stuff appears to be very sensitive. Hopefully the ground plane on the carrier is able to alleviate some of the tendency to be unstable.

Dennis

[xtal]

Has anybody considered the pulse count method, I've seen a couple of 555 timer chips with probe attached, the count represents the salinity level..

I'm wanting to measure my pool water, salt ppm[4000-6000uS/cm] , and ph,Temp and transmit over 1-wire

Did find that somebody recommended titanium wire [ available from McMaster] for probe

also found 3 conversion factors
EC * 500 [USA] = ppm
EC * 640 [EU] = ppm
EC * 700 [AU] = ppm
my biggest problem is creating satisfactory calibration solution 2000 ppm, 3000 ppm
did breadboard a 555 seemed to work but was temperature sensitive.

[pringlescan]

Why does it differ by country?

I ordered a jewelers scale and some lab implements I plan to make my own solutions. I haven't figured out how I want to do it yet, but that seemed like the bare minimum I'd need for precise measurements. EC test solutions are expensive and way outside the range most are testing for. I think 50,000 us/cm is equivalent to seawater. I was unable to find any solutions close to that.

Originally Posted by xtal

Has anybody considered the pulse count method, I've seen a couple of 555 timer chips with probe attached, the count represents the salinity level..

I'm wanting to measure my pool water, salt ppm[4000-6000uS/cm] , and ph,Temp and transmit over 1-wire

Did find that somebody recommended titanium wire [ available from McMaster] for probe

also found 3 conversion factors
EC * 500 [USA] = ppm
EC * 640 [EU] = ppm
EC * 700 [AU] = ppm
my biggest problem is creating satisfactory calibration solution 2000 ppm, 3000 ppm
did breadboard a 555 seemed to work but was temperature sensitive.

[xtal]

I would suspect the reason for the difference in the conversions would be they're different chemicals for their standard [just guessing]...

If my thinking is correct 6000 us = 6 mS/cm * 500 =3000 ppm
also 6mS/cm = .006 S/cm => mho Therefore
R = 166 ohms
R@.004 =250 ohm
R@.005 =200 ohm
R@.007 = 142 ohm

So I would want a probe to be reliable from 4000us-7000us, 142-250 ohms.

I think a K =1 , but not sure mechanical demensions
I did see a description of 2 1cmx1cm plates separated by 1cm , but not sure if I under stood this correctly...

[xtal]

Have completed a pulse counting TDS meter, my problem now is I need several good calibration solutions, and a good k 1.0 probe..

The pulse circuit is LM555 timer timer chip [ similiar to atlas scientific] which feeds a 16f1825 pic running 32mhz... The 555 circuit itself appears to be temperature sensitive. And requires more investigation. I have attached the source code -in proton basic and a hex file..
In case anyone is interested...

It captures pulses for 32000 us into T1 ctr, I have captured 64000 counts reliably. I take 8 samples of the pulses and also of the temperature [DS18b20]
I have 5 Probe tables that will hold 10 calibration ppm/count values each
you have to manually add the values with a command [ RS232 ] other command are available - see source code

I have some test code using port c to derive Bipolar signal from op amp
-was trying to play with pulse TDS measurement

My current timer is using a .022uf cap and with 150 ohm {probe-resistor}
I get approx 44000 pulses, If I place my finger on the 555 chip the pulse rate slowly drops to 43000+ [ ie temp sensitive]

If I can come up with a good probe and embed the DS18b20 I think it will be a viable design

[dartier]

Originally Posted by dartier

Ugh, I just order the Atlas EC kit a few days ago. It is certainly not cheap, I just hope it works as expected.

I already have their ORP and Oxygen. The Oxygen has worked fine, buy the ORP has been very sensitive to other electrical interference. I attribute it to the EMI thrown off by my PWM lines driving my Meanwell boards. The readings would become crazy as soon as my LEDs would kick on for the day. To help counter this I changed my PWM lines to using shielded CAT-5 for the longish run to the lights. This helped somewhat. My Oxygen probe became useable, the ORP not so much. So for this order I added one of their carrier boards so that I can try to isolate the probe circuits into a remote shielded box near the tank.

The Atlas Scientific stuff appears to be very sensitive. Hopefully the ground plane on the carrier is able to alleviate some of the tendency to be unstable.

Dennis

Just to follow up on my post above about the Atlas Scientific EC probe. Another failure, I was not able to get it to be reliable. It would drift out of calibration over a matter of days. I never figured out what the issue was. At first I thought my grounding probe may have been the cause, but that was short lived.

Of the 3 kits I ordered (ORP,EC, DO), I was only ever able to get the Dissolved Oxygen one working reliably. Some people report good results with their stuff, but that has not been my experience.

Dennis