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Topic: Help with Ph sensor pin abbreviations (Read 64219 times) previous topic - next topic

crustyourmind

OK thanx

And finally, the temperature sensor is functional?

Thx and good day ;)
Débutant Arduino (UNO/NANO).... Mais motivé...
-------------------
IDE Arduino 1.8.8 Debian SID
IDE Arduino 1.8.5 FreeBSD

wvmarle

And finally, the temperature sensor is functional?
I may assume it is. I've never tried it as it has several issues.
1) parameters of the sensor (a thermistor) are not known, so I have no idea on the actual temperature response.
2) the signal is fed through a cascade of total three(!!) OpAmps.Too hard to figure out that that does to the signal.
3) it's measuring the air temperature rather than the water temperature.

Note that the thermistor circuit is completely independent from the pH circuit, they only share the power supply. For some reason the majority of the components on that board are in fact related to the thermistor. It's overall a quite odd and seemingly overcomplicated circuit.
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.

crustyourmind

Débutant Arduino (UNO/NANO).... Mais motivé...
-------------------
IDE Arduino 1.8.8 Debian SID
IDE Arduino 1.8.5 FreeBSD

porlock

....
According to the schematic, the final op amp output should be a 2x........
Can you share schematic?

wvmarle

Schematic of that sensor board you can quite easily find online.

Do note that the pH is a bit temperature dependent so for best results use a water temperature probe (waterproof thermistor or digital D18B20 sensor).
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.

crustyourmind

I received this board yesterday

To calibrated it , I putted the probe in water with ph 7.2 and I calibrate the data with the blue potentiometer close to BNC

I tested in my aquarrium : 7.4, my coffee 4.9 and lemonade lemon juice 3.5

I think, it works.

Thanx for this thread ;)
Débutant Arduino (UNO/NANO).... Mais motivé...
-------------------
IDE Arduino 1.8.8 Debian SID
IDE Arduino 1.8.5 FreeBSD

wvmarle

It works - but your calibration will be off. Water is NOT suitable for calibration, you must use a buffer solution. Preferably two.
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.

crustyourmind

OK thx, I'll looking for 2 buffer solutions

Now I ' try to calibrate the limit red led
Débutant Arduino (UNO/NANO).... Mais motivé...
-------------------
IDE Arduino 1.8.8 Debian SID
IDE Arduino 1.8.5 FreeBSD

crustyourmind

I've Just tested with 2 buffer solutions received today

So at 4.01 PH, I've got theses value :  mesure 601 and voltage 2,95

The ph-step is : 2,95 - 2,5 / 2,99 = 0,15

I've adjust this var is this formula
  // PH_probe = PH7 - ((voltage@PH7 - voltage@probe) / PH_step)
  float Po = 7 + ((2.5 - voltage) / 0.18);

And it works fine

I check with the second buffer solution (6,86) and the return is 6,82, so I consider this value acceptable

A great thx for your help
Débutant Arduino (UNO/NANO).... Mais motivé...
-------------------
IDE Arduino 1.8.8 Debian SID
IDE Arduino 1.8.5 FreeBSD

Krheigh

I have this sensor an have hard time to get it work.
I think it's broken.
No matter how many turns (both ways) I screw the pot closest to bnc I only get 4,95v out of OP pin.
Bnc shorted.

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