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Topic: Help with Ph sensor pin abbreviations (Read 65253 times) previous topic - next topic

porlock

ground the water in aquarium, electrical pumps and heaters can cause this.

Coos

Do you know a simple way to do this?

porlock

Use a titan (for salt water) on staines steel pipe, attach a ground wire to it ant connect to wall socket ground, i do it this way.

You can also find a plug and play solutions like for example this one

https://www.amazon.com/RV2735-Rid-Volt-Titanium-Grounding-Probe/dp/B0002DGSWE

tigger

If you ran your amplifier on an isolated supply like a battery, you might get rid of problems caused by ground loops. Measuring pH is simple if you follow the rules. The electrode is a high (very) impedance source and doesn't like things like long cable runs or even being touched. You need a FET, very low bias op amp close as possible to the electrode to buffer the electrode output from high to low impedance. Look up Maxim MAX406 datasheet for an example of how to do it. You can run an op amp circuit on a 3-volt battery for at least 10 years.
One of the problems is down to the practice of supply utilities using a system called PME or Protective Multiple Earthing, where the Neutral is earthed and no earth is supplied to the property. You buy a two pin PSU (no earth) and it is connected to earth via the neutral, hence the possibility of a ground loop. In industrial situations, ground loop problems with pH are a pain and the only answer sometimes is to go for the isolated supply.

agatho

#49
Feb 06, 2018, 07:26 pm Last Edit: Feb 06, 2018, 07:32 pm by agatho
Help me, i tried the program on page 1, i have done calibration, by short the BNC pin, and getting 2.6 v
1. after that I tried with a solution of 6.89 and can not produce 6.89 but lebh of it smpai value 7.3
2. then when trying 4.01, the resulting value is more than that 4.8

What makes me confused when the BNC probe on boar I hold, the results obtained even precision, when released value will be chaotic, what happens from my board?

I connect directly
Pin VCC to 5volt arduino mega
Pin G to Ground arduino mega
Pin P0 to A0 arduino mega

please help me, thanks

wvmarle

Apparently you missed the part of calibration where you adjust the slope and offset in your software to match the sensor's response.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

JohnTaylor

Hi all,

I think this thread is really great because it is the sole source of information on this pH sensor board. Thank you so much for contributing to it and providing so many useful details.

I'm posting here because I'm encountering an issue with the first step of the calibration. The pins are connected as follow:
- V+ to 5V
- G to the ground of the my power source and the COM port of my multimeter
- Po to the V port of my multimeter
- Do and To to nothing
In addition, I used a wire to shorten the BNC connector.

When I adjust the potentiometer by the BNC connector, nothing happens on my multimeter which continuously reads 1.88V. If I remove the wire used to shorten the BNC connector, the voltage remains the same.

Does that mean that my board is defective/broken?

CrassHoppr

Hi All, I've got the same Ph module, and found this thread very useful!
Special thanks to LeCyb and normen!

I've got one problem though:
When I measure my aquariumwater in the tank the ph goes all over the place, from ph4 to ph8...
When I measure the same water in a cup, I'm getting a steady reading.

So something is interfering I guess...
Anyone got an idea of how to approach and solve this problem?
Same problem here..  As soon as I put it in the voltage goes crazy with random values, but I can take a cup of the same water and it is fine.  like porlock I assumed this must be some piece of equipment causing it so I unplugged everything and it is still occurring.  I also notice as soon as the probe goes in the aquarium the red limit LED on the board comes on and stays on. 

Did you ever solve this issue?  I wonder if my issue can be solved by a grounding probe if it still occurs when no equipment is connected?

wvmarle

Sounds like you're having ground loop issues. Can be very hard to solve.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

CrassHoppr

Sounds like you're having ground loop issues. Can be very hard to solve.
Yes I think you are correct.  I did some testing and powered my board from a battery and while the voltage swings were higher than I liked they were no longer wildly fluctuating. 

From my research it looks like I can either try to isolate the ph probe or isolate the entire circuit.  I found some dc/dc isolated converters like this that look like they should work.  This will mean another pcb revision which is annoying, unless anyone knows of a 5v wall adapter that has an isolated converter in it?

wvmarle

For your wall adapter: any with a transformer in it should give you full isolation.

Mind that ground loops are generally within your circuit, so through other sensors in the water (such as EC probes or temperature probes).
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

DR2727

Hey guys,
Has anyone encountered an issue where the pH value keeps climbing on its own (given like a 2 min. span) and won't keep stable?
I have my probe sitting in factory calibrated 7.0 pH solution, so I know that it's not a solution issue.
Any help/advice would be great!

Here's my sketch as it is:

Code: [Select]

/* 7.0 Solution
 *  Measure: 512
 *  Voltage: 2.5
 *  PH: 7.0
 *  
 *  4.1 Solution
 *  Measure: 619
 *  Voltage: 3.02
 *  PH: 4.01
 */

int Po_Pin = A0; //Pin Po on the pH sensor board connects to Arduino pin# A0.
int Do_Pin = 2; //Pin Do on the pH sensor board connects to Arduino pin# 2.

void setup()
{
  Serial.begin(9600);
}

void loop()
{
  int measure = analogRead(Po_Pin);
  Serial.print("Measure: ");
  Serial.print(measure);

  double voltage = 5 / 1024.0 * measure; //Digital to Analog conversion
  Serial.print("\tVoltage: ");
  Serial.print(voltage, 3);

  //PH_step = (voltage@PH7 - voltage@PH4) / (PH7 - PH4)
  //PH_probe = PH7 - ((voltage@PH7 - voltage@probe) / PH_step)
  float Po = 7 + ((2.5 - voltage) / 0.173);
  Serial.print("\tPH: ");
  Serial.print(Po, 3);

  Serial.println("");
  delay(100);
}

 

wvmarle

Most probes take that long or even longer to stabilise.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

DR2727

#58
Apr 22, 2018, 07:08 am Last Edit: Jul 13, 2018, 10:28 am by DR2727
@Mvrale

Thank you very much for the advice.
I let my probe sit for 20 minuets and the readings seemed to stabilize.

Laurencet

Hi All

Just bought an Arduino due that has a maximum input voltage of 3.3v, I thought the 12 bit Dac would be a bonus.
I'm guessing that there is a high chance that I could exceed the 3.3v and blow the Due,
do I need to put a 3.3v voltage regular inline to stop me blowing up the arduino?

 I'm only interested in between PH6 and PH 8


Thanks




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