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 Post subject: Hydroponics and Aquaponics - difficulties calibrating the pH
PostPosted: Mon Mar 14, 2016 9:28 am 

Joined: Fri Mar 11, 2016 9:56 pm
Posts: 3
We bought the pH and EC extension shields for Open Garden and Open Aquarium and we are experiencing the same issue with either combination of the boards and pH sensors (We have two of both). :

The measured mv values are rather low, between 250 and 600 depending on the pH of the testing solution and the values are varying widely. The signal noise is in the range of 50% so when measuring a mean value of 350 mV, the values fluctuate between 250 and 500, even between two measurement cycles.

In the example code the calibration values in the upper section are in the range of 2000mV:

Code:
#define calibration_point_4 2246  //Write here your measured value in mV of pH 4
#define calibration_point_7 2080  //Write here your measured value in mV of pH 7
#define calibration_point_10 1894 //Write here your measured value in mV of pH 10


So I guess there is something fundamentally wrong with our setup and we are actually measuring noise and not signal.

Any recommendation on how to proceed?


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 Post subject: Re: Hydroponics and Aquaponics - difficulties calibrating th
PostPosted: Tue Mar 15, 2016 8:40 am 

Joined: Mon Sep 28, 2009 11:06 am
Posts: 10560
Hello jsilence,

in order to discard if the failure comes from Hydroponics board please do the following.

Load Example: Read Gateway Sensors -> Hydroponics Sensors -> readpH

Remove the pH connector from hydroponics board and join with a cable the internal terminal with the outside as in the image:

https://dl.dropboxusercontent.com/u/102 ... 115541.jpg

When opening serial monitor you should receive a stable value similar to this:

Code:
pH Value in 2104 mV = // pH = 6.57

Regards


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 Post subject: Re: Hydroponics and Aquaponics - difficulties calibrating th
PostPosted: Fri Mar 18, 2016 12:13 pm 

Joined: Fri Mar 11, 2016 9:56 pm
Posts: 3
libelium-dev wrote:
Load Example: Read Gateway Sensors -> Hydroponics Sensors -> readpH
[...]
When opening serial monitor you should receive a stable value similar to this:

Code:
pH Value in 2104 mV = // pH = 6.57



Hello libelium-dev,

I proceeded as described and got the following readout on the serial monitor:

Code:
pH Value in mV = 1987 // pH = 8.50
pH Value in mV = 1987 // pH = 8.50
pH Value in mV = 1987 // pH = 8.50
pH Value in mV = 1987 // pH = 8.50


Is that close enough?
So the pH-electrodes are not ok? How can I diagnose that?


Best regards,

-rolf


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 Post subject: Re: Hydroponics and Aquaponics - difficulties calibrating th
PostPosted: Mon Mar 21, 2016 8:04 am 

Joined: Mon Sep 28, 2009 11:06 am
Posts: 10560
Hello jsilence,

please could you send us a photo of your hardware configuration and sensors when you are calibrating, for example with pH 7?

Does the values oscillate when you leave the sensor still in the solution for some minutes?

Regards.


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 Post subject: Re: Hydroponics and Aquaponics - difficulties calibrating th
PostPosted: Wed Aug 03, 2016 4:07 am 

Joined: Wed Aug 03, 2016 3:41 am
Posts: 1
Hello,

I have some problems with py ph and EC sensors. After doing the test readPH with a cable in the ph internal terminal I read

pH Value in mV = 2050 // pH = 9.22
pH Value in mV = 2050 // pH = 9.22
pH Value in mV = 2055 // pH = 9.01
pH Value in mV = 2055 // pH = 9.01
pH Value in mV = 2055 // pH = 9.01
pH Value in mV = 2050 // pH = 9.22

Is it normal?

On my side, when I want to read ph or Ec, the whole arduino loop just stops randomly. Sometimes it reinitialize, sometimes not. Sometime an annoying noise is thrown.

Thanks for the help


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 Post subject: Re: Hydroponics and Aquaponics - difficulties calibrating th
PostPosted: Mon Aug 08, 2016 7:04 am 

Joined: Mon Sep 28, 2009 11:06 am
Posts: 10560
Hello gkfabs,

yes, the value that you receive is normal. Are you using Arduino Uno and Arduino IDE 1.0.5. Could you send us some photos of your hardware?

Regards


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