Why measuring pH?

You can discover pH meters for your applications here section - for your use in the laboratory or for mobile pH measurement on the road.

pH is the most important most frequently measured value in aqueous solutions. Roughly speaking pH defines if a solution is acid, neutral or alkaline. It is bases on the dissociation of the water molecule H₂O ⇔ H⁺+ OH^- and describes the activity of the hydrogen ion. The scale it includes according to the definition 14 orders of magnitude from 0 to 14. Solutions between 0 and 7 are acid, exactly at 7 they are neutral, between 7 and 14 alkaline. The smaller the pH the higher the activity of the hydrogen ions and vice versa. In practice values between -1 and 15 can be measured.

The sensor for pH is the so-called pH electrode, consisting of a measuring electrode and a reference. The measuring electrode consists of a special glass sensitive for hydrogen ions. It is filled with a buffer solution with pH 7. Immersing the electrode into a sample leads to change of the potential of the measuring electrode in comparison to the reference. This change will be detected by appropriate instruments and converted to the pH reading.

The pH measuring instrument or pH meter has the task of converting the voltage generated by the pH electrode used (also called pH electrode) into a pH value. To do this, the pH meter must determine the characteristic curve of the pH electrode used in each case by means of calibration and correct it to the ideal values (59.2 mV/pH slope and 0 mV zero point deviation). Modern pH meters - whether portable or laboratory - have high-impedance input electronics (> 1012 ohms) to safely process the sensitive measurement signal and convert it into a reproducible digital signal. The resolution of the pH value in the display can be adjusted with the desired decimal places on many instruments according to user requirements. With the digital IDS pH electrodes, the measuring electronics are already integrated in the sensor head.

Our pH buffer solutions are of course traceable to modern international standards. Here you can order all pH buffers of the brands WTW and SI Analytics.

Order your pH-Buffer here

Here you can see and download all pH buffer certificates at a glance.

pH buffer certificates

Further information of the topic of pH/ORP you can find here in our blog articles "FAQ pH measurement" and "What is the pH value?". As a customer, you can benefit from the helpful practical tips and experience of our expert on topics such as the correct pH measurement, handling, cleaning and care as well as calibration and adjustment of pH-electrodes.

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Why measuring ORP?

The measurement of the oxidation/reduction potential (ORP) is based on reactions taking place in aqueous solutions, where the reactants exchange electrons. The uptake of electrons by one reactant is called reduction, the donation of electrons by the other oxidation.

An ORP electrode makes this reaction visible. It consists of an inert precious metal electrode (gold, platinum) and a reference electrode. The reaction of the reactants on the metal surface causes an electrical potential in comparison to the reference electrode which can be detected by appropriate meters. A typical application in practice is the monitoring of the efficiency of a disinfectant dissolved in water like chlorine. The potential of an ORP electrode will always be noted considering the reference system used (typically Ag/AgCl). If the conversion into the potential versus a hydrogen electrode is required a temperature dependent potential has to be added (e.g. 207 mV at 25 °C).