measure the pH - a comparison of the various mehtods

Thread Starter


Joined Aug 15, 2018
hello dear Community,

first of all i hope that you are well and everything goes all right at your hometown. I hope that your town is dealing well with the pandemic-situation.

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?


Joined Dec 13, 2021
How accurate is the Litmus paper
How accurate is the Ph meter without calibration ?

I'm wondering is the Ph meter without calibration as good as litmus paper ?

Thread Starter


Joined Aug 15, 2018
hello and good day dear drjohsmith,

first of all: many many thanks for the reply. Well i guess youre right. I think therefore i have to use

a. dfrobot - Sensor
b. Atlas-EZO-Sensor

the bad thing is that all of these sensors need a permanend calibration -

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

vom pH wert

and what bout this approach; working wiht LIGHT SENSORS - SPECTRAL SENSING AS7264N
AS7264N Consumer Grade Smart XYZ + Bio-Blue + NIR Sensor

XYZ Color Point/CCT identification plus 440/490nm blue sensing


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
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
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

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!?

well - that looks interesting -
courtesy: see
[attachment=0]2022-02-01 15.28.30 1e0e4e9b12dd.jpg[/attachment]

courtesy: see



Joined Sep 17, 2013
I'm not sure this is a topic I have a lot to say about personally, but I did find a couple of links that I consider worth taking a look at:
I guess neither one of them is "completely devoid of calibration" but isn't it more about how frequently it's necessary to redo that calibration? Again I don't know quite what the issue is so I'll refrain from trying to take this further.