EC and pH with Arduino

Hey guys,

this is my first post in this board so: Hello to everybody :)

A friend of mine (who studies electrical engineering) and myself are starting a new project that requires to constantly measure the pH and EC of water enriched with nutrients.

I researched for nearly 3 days now and found different solutions. But I recognized that you pretty much have to buy a pH probe, a EC probe, and a shield oder adapter for both EC and pH seperately. Summing up it will cost me about 150€ or 200USD.

I am wondering if you know any other possibilites to realize this with spending a bit less money. We need the pH-values, for example, .1 accurate so most laboratory stuff will be a total overkill.

I hope you can help me with this! Thanks a lot in advance - we are looking forward to your posts.

have you checked atlas scientific? - https://www.atlas-scientific.com/index.html -

robtillaart: have you checked atlas scientific? - https://www.atlas-scientific.com/index.html -

Hey rotillaart,

yes I did. The solutions they are offering seem pretty confident. The thing is that both shields (conductivity and pH) cost together around 70€/95USD. In addition to this the probes cost around the same which would also sum up to 150€/200USD in the end.

I thought if it is maybe possible to buy this handy EC/pH Multimeter (http://www.ebay.de/itm/PH-Messgeraet-Leitwert-ph-meter-ph-EC-Leitwertmesser-Aquarium-EC-Wert-NEU-/141015949180), open it and try to pick up the data. What do you think about that? Do you think that could work?

Cheers, kaul

Of course it could work, but there are a some points - is the device adequate , does it measure accurate/precise enough. - how about calibration of the device? can it be done? - if you get a signal, what does it mean, can you reverse engineer it. E.g. understanding of non linear analog signals are non trivial at best. (collect reference values and make a lookup table / interpolate is SW) - if it does not work you loose $70 (and several weeks) of your budget.

There are several threads on this forum about PH measurement (e.g. science & measurement section) and maybe you should go through them and contact the people.

my 2 cents Rob

I bought a cheapish ph probe and it seems to be fairly accurate.

If memory serves me correctly I used this circuit. (or something close to it)

http://www.tradeofic.com/uploadfile/ic-circuit/200962520412682.gif

Update: Here is the exact circuit I used:

www.electro-tech-online.com/attachments/ph_amplifier-pdf.21692

Hey GregM,

thank you very much for your response. Unfortunately I dont feel confident enough to build by own circuit by now.

I found this pH/ORP adapter (http://www.eztronics.nl/webshop2/catalog/Sensor?product_id=119) that is only about 27€ and allows me to connect any BNC probe and gives out an analog signal. The probe (http://www.eztronics.nl/webshop2/catalog/Sensor?product_id=346) is about 25€.

It seems that for pH measuring there are cheaper solutions than for measuring conductivity. Maybe it is a stupid question but would it work to connect an EC probe that has an BNC connector and also use the pH/ORP adapter mentioned above?

Thanks again for your expertise and answers!

P.S. Thank you also for your answer, robtillaart. I think you convinced me of not using this device. However my idea was to use the signal that is sent to the display. Stupid idea?

Cheers, kaul

[eztronics] eztronics.nl is a company with good service (I ordered there in the past) but be aware that this is only an adapter, it does not include the sensor. But they have a sensor which is not as expensive as the other one. see - http://www.eztronics.nl/webshop2/catalog/index.php?route=product/product&product_id=346 -

[sniffing display] signal sent to the display could work, six 7 segment displays means 42 IO lines => can be done with 6 I2C PCF8574 ... but how to be sure that you read correct. when the value is updated from 9.9 to 10.0 (or the other way around) then it depends on the order of the segments you read if the value is correct. OK chances are not that big but it will occur once and a while giving you a sudden jump in reading.

@robtillaart: thank you for your constant support!

[eztronics] Yes, eztronics looks good. Unfortunately I did not find a solution for EC there. The adapter is for pH only, right? How do I get the data from the probe into my arduino then?

[sniffing display] can you explain in a bit more detail how you think I could work to extract the data? I don't know the PCF8574 unfortunately.

I hope my questions are not too dumb :(

Thanks a lot!

Let's say I would use the Conductivity Sensor from Atlas Scientific (https://www.atlas-scientific.com/product_pages/embedded/ec.html), would it be possible to connect another probe than the ones from Atlas?

The question came up because when it comes to calibrating the probes, you have to select one of the three offered probes, as you can see from the manual: The three probes are: