Measure the pH - a comparison of the various mehtods:

Using Arduino Project Guidance
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hello dear Community,

i have mused alot about the methods of the measure of pH - a comparison of the various mehtods: we can measure the pH of a substance several ways.

A pH meter is one of the most common methods, and pH paper (also known as litmus paper or pH strips) is also a quick and dirty way. Other methods include titration, but it is tedious and requires detailed hands-on work.

what about a comparison of pH detection methods.
we have the pH Meter with the glass pH electrode. A pH meter has a membrane that allows acidic ions (H+) to pass through it creating a voltage. The meter associates each voltage with a particular pH value.
How it works: The higher the concentration of acid is, the more interesting are the results - the more ions that will pass through the membrane, thereby changing the value of the voltage.
This voltage change results in a higher pH value.
on the other handside: The Litmus Paper - It doesn't pass the litmus test - is a common phrase that has its origin in the use of litmus paper for pH detection. So far so good.
How it works: the so called strips of paper - they have so called littel (we ought to say very little) pH indicator molecules that subsequently change color upon contact with solution of a particular pH.
And this is the interesting point: Each color is indicative of a particular pH value. We can compare the paper to a standard chart where the colors show different pH values.

BTW; i have mused about the pH-Measurement with Atlas-pH sensors that are combined with ESP 32 or Arduino or RaspBerry-Pi. And i have also mused about the usage of DFRoot Sensor.

The bad thing is that all of these sensors need a permanend calibration - this is awful.
Question Can i go round this calibration - if i am going to use Litmus Paper that is checked and indicated with a opto-electronical process.
In other words -i take tha Litmus (pH) paper and let the opto-electronic stage generate a value - a certain voltage.- With that i will set a display that shows the current value of pH of my actual probe

How do you like this idea. Can this be done?

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What does the manufacturer datasheet say?

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hello and good dear Railroader

first of all many many thanks for the quick reply - awesome to hear from you.
i like your ideas that you share here. I have to have a closer look at the manpages and the datsheet of the manufacturer.

dfrobot - i have seen this - and y es: i really like it. : cf: https://www.dfrobot.com/product-1025.html
Gravity: Analog pH Sensor / Meter Kit For Arduino

INTRODUCTION> Gravity: Analog pH Sensor / Meter Kit For Arduino Overview

You may check the latest version - Gravity: Analog pH Sensor/Meter Kit V2 to meet your requirements and Liquid Sensor Selection Guide to get better familiar with our liquid sensor series.
Need to measure water quality and other parameters but haven't got any low-cost pH meter? Find it difficult to use with Arduino? DFRobot analog pH meter, specially designed for Arduino controllers and has a convenient and practical "Gravity" connector and a bunch of features. Instant connection to your probe your Arduino to get pH measurements at ± 0.1pH (25 ℃). For most hobbyists, this great accuracy range and its low cost make this a great tool for biorobotics and other projects! It has an LED that works as the Power Indicator, a BNC connector, and a PH2.0 sensor interface. To use it, just connect the pH sensor with the BND connector, and plug the PH2.0 interface into the analog input port of any Arduino controller. If pre-programmed, you will get the pH value easily. Comes in a compact plastic box with foams for better mobile storage.
Build your own PH meter gadget or a water monitoring station for your water tanks. This and our other water sensor devices could make for the ultimate water control device. Use it for your aquaponics or fish tanks or other materials that need measurements.
This is a laboratory probe, it can't be immersed in the liquid for too long time. You can check here for the whole Analog pH Sensor / Meter Pro Kit For Arduino or a spare Industrial Probe as a replacement

btw another interesting method:

LIGHT SENSORS - SPECTRAL SENSING AS7264N
AS7264N Consumer Grade Smart XYZ + Bio-Blue + NIR Sensor
XYZ Color Point/CCT identification plus 440/490nm blue sensing

see AS7264N XYZ sensor - human eye color response | ams

Features
Integrated interference filters directly deposited on standard CMOS silicon
XYZ filters + 440nm + 490nm + wide banded NIR band passes
Integrated 16 bit ADC on chip and low power consumption
2 integrated LED drivers
I²C slave digital interface with optional interrupt operation
Benefits
Stable filter conditions over temperature and life time
Human eye like color, light, good+bad blue and proximity detection
Signal conditioning on chip
Sample illumination without external LED driver
Direct register read and write with interrupt on sensor ready
Product parameters
Sensor Type 6 channel visible + NIR
Applications CCT and Color Point identification plus added blue
I/O I²C
Package 20-pin LGA
Size [mm] 4.5 x 4.7 x 2.5
Supply Voltage [V] 2.7 to 3.6
Temperature Range [°C] -40 to 85[/quote]

well - that looks interesting -

courtesy: see AS7264N XYZ sensor - human eye color response | ams

hmm - i guess that i have to muse bout this. Do you tink that i can use it to measure the ph via going the way over working

a. with the litmus paper comes on continuous rolls?
b. then have a closer measure with the IR sensor!?

a. with the litmus paper comes on continuous rolls?
b. then have a closer measure with the IR sensor!?

But in the meantime - there is also another method with Fibre: see PreSense

that sounds interesting

love to hear what you think!?

that sounds interesting

love to hear what you think!?

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You have alternatives to investigate. Good. You also have the sensor and can try it. I have no sensor and can't try. I will also not spend time reading what You have found.

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Measuring pH as you find out is difficult and do require daily calibration if you want accuracy. If you want to distinguish acid from basic liquid then the paper method migth be enough. It depend on your needs.

I also played with the Atlas sensor. Not only it need frequent calibration but you also need to compensate for temperature (like all sensor of this kind by the way).

Trying to "build" a color to pH sensor (I think this is what you suggest?) might be good if you don't need more accuracy than the strip chart. And fun!

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Couldn't agree more, Railroader. Oddly, this seems to be a common question:
reddit. com/r/arduino/comments/sforee/measure_the_ph_a_comparison_of_the_various_mehtods/hva0ekw/?context=3

OP is there a point? I mean its a fine project but you're delusional if you think you're going to build a measurement device (that's not a tape measure), that'll never, EVER need calibration, especially for measuring ph.

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A frequent concern here is the expectation to continuously record pH.

Apparently not your expectation and of course using pH ("Litmus") papers mandates individual measurements using strict consumables. Continuous recording is "a whole different ball game". :astonished:

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