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Topic: Help with Ph sensor pin abbreviations (Read 66757 times) previous topic - next topic

wvmarle

Use a voltage divider instead.

Use quality resistors for this - especially with low temperature coefficient (50 ppm or better) or your measurements will be very off when the temperature changes (this doesn't negate the temperature correction on the pH reading itself).
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.

Watcher

Hi all
 Veey interesting thread!

Which probe did you guys use?
There seems to be two types on ebay..a black and a bluish coloured one!
Any comments on those?

wvmarle

I got (separately) an "industrial" type probe, which is designed to be in the liquid constantly. Good change the probes you see on eBay are "lab" type probes, those can not remain in the liquid you want to test all the time. Check the description!
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.

Watcher

#63
Oct 09, 2018, 06:24 am Last Edit: Oct 09, 2018, 06:27 am by Watcher
I got (separately) an "industrial" type probe, which is designed to be in the liquid constantly. Good change the probes you see on eBay are "lab" type probes, those can not remain in the liquid you want to test all the time. Check the description!
I didn't see any note on the description that it is not designed to remain in the liquid all the time.
But yes, I intend to use it to constantly monitor he Ph of my pool water.

Which probe did you buy ?

wvmarle

No brand... got an inexpensive one off Taobao.
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.

Watcher

No brand... got an inexpensive one off Taobao.
Care to share the link ?

wvmarle

https://item.taobao.com/item.htm?spm=a1z0k.6846577.1997989141.5.219937dexP9meN&id=520287697860&_u=

This one.
Haven't been able to verify it against calibrated probes but it seems to do the job quite well.

I'm in the process of building my own pH amplifier (designed to amplify in the 0-1V range, instead of the 2-3V range that this pH sensor board does - that way it can be read using the internal reference for much higher resolution and accuracy). When that's done I'll be doing more thorough testing as well.
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.

Watcher

#67
Oct 09, 2018, 08:27 pm Last Edit: Oct 09, 2018, 08:28 pm by Watcher
Opps..its all in chinese!

I try to do Google translation  but it didn't work.  I am not even able to complete a purchase!   :smiley-confuse:

wvmarle

Yes... that's Taobao. Only Chinese.

They have international shipping methods (I routinely buy from that site - shipping to Hong Kong) but you have to be able to manage the Chinese part. Google Translate helps, for everything else there's the missus :-)

Aliexpress is the international version of Taobao.
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.

Watcher

ok thanks!

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

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

wvmarle

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.
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.

Watcher

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.

bjett80

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.

crustyourmind

Hi
I 've just buy it ;)
Do you think that the PH electrod can stay all the time in the aquarium ?
Thx ;)
Débutant Arduino (UNO/NANO).... Mais motivé...
-------------------
IDE Arduino 1.8.8 Debian SID
IDE Arduino 1.8.5 FreeBSD

wvmarle

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.
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.

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