Help with Ph sensor pin abbreviations

ok thanks!

It looks like I will have to search in Aliepxress instead!

So its possible to find the same seller/ item in Aliexpress?

You can almost certainly find the same item from like a dozen sellers on AliExpress - but I don't expect you to find the same seller there. That said, there are many pH probes out there. Quality varies. This one I expect is of the type that gets the job done but won't have too great precision.

Yes i understand.

In my application, it will be permanently installed on one of the swimming pool's water pipes to monitor the pool Ph on running water. The arduino will then switch on a peristaltic pump to inject acid when needed.

As was mentioned in a much earlier post, the thermistor output did not appear to be functional.

I just acquired one of these and noticed my temperature (T0) output was always at 3.47 volts, regardless of the thermistor output.

According to the schematic, the final op amp output should be a 2x multiplier using a 20k to 10k voltage divider at the output (pin 7) of the op amp. This 20k resistor is actually a 51k resistor on my board, making the gain so high that the output is saturated at 3.47.

I was able to make the T0 output work by replacing this 51k resistor with a 20k resistor, giving me a 2.69 volt output on T0 that now changes with temperature.

The resistor in question is labelled R22 on the schematics and is the smd resistor to the immediate left of the top right eyelet assuming the BNC connector is pointed to the right.

The original poster was from 2016 .... so I'm confused why, if this is a manufacturing error, it is still not fixed in 2018.

Hi
I 've just buy it :wink:
Do you think that the PH electrod can stay all the time in the aquarium ?
Thx :wink:

The one I linked to? Should be perfectly happy that way. It's actually the type that you have to keep wet at all times.
I've used it for a few months straight at one time, no issues. Removed again due to ongoing experimenting and tinkering.

OK thanx

And finally, the temperature sensor is functional?

Thx and good day :wink:

crustyourmind:
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.

Thx for your answer
It's too bad that the temp sensor measure the air temperature rather than the water temp

I'll not use it. Therefor , I'll use a small LDC screen with only the PH value...

But in the comments, a buyer seem to have a temp value (the second picture of this link https://fr.aliexpress.com/item/1Set-Liquid-PH-Value-Detection-Regulator-Sensor-Module-Monitoring-Control-Meter-Tester-BNC-PH-Electrode-Probe/32805675619.html?spm=a2g0w.search0104.3.10.45996e1dtOVqSR&ws_ab_test=searchweb0_0,searchweb201602_1_10065_10068_319_10892_317_10696_10084_453_454_10083_10618_10304_10307_10820_10821_537_10302_536_10843_10059_10884_10887_100031_321_322_10103-10892,searchweb201603_6,ppcSwitch_0&algo_expid=6da752a5-1cea-4e8b-b57b-720ae8b90f9e-1&algo_pvid=6da752a5-1cea-4e8b-b57b-720ae8b90f9e

bjett80:
....
According to the schematic, the final op amp output should be a 2x........

Can you share schematic?

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).

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 :wink:

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

OK thx, I'll looking for 2 buffer solutions

Now I ' try to calibrate the limit red led

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

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.

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.

Same problem on 2 different boards. Still looking for a solution :frowning:

Saya memiliki masalah. Sensor pH saya nilai pH rendah output nilai ADC ikut rendah sedangkan nilai pH tinggi output nilia ADC ikut tinggi dimana hasil yang saya dapat tidak akurat atau diatas nilai 14 pH. Mohon bantuannya

Idk if this has already been posted. But someone has done all the hard work with this sensor. I think everything you'll need to get it working will be here:

https://scidle.com/how-to-use-a-ph-sensor-with-arduino/