ISFET pH Products

Standard pH Products

More insight into Wellinq’s comprehensive pH meter line of quality meters and probes for glass-free pH measurements, created for Sentron’s proprietary ISFET pH sensor.

Wellinq has developed a comprehensive line of quality meters and probes for non-glass pH measurements. The SI line of meters and probes is created for Sentron’s proprietary ISFET pH sensor technology that offers accurate and reliable pH measurement for demanding applications.


An ion-sensitive field-effect transistor (ISFET) is used for measuring H+ ion activity in solution. Besides the ISFET electrode a reference electrode is required, for which Wellinq has developed tiny, stable designs compatible to medical and food safety standards. The principle is that when the H+ activity changes, the current driven voltage will change, and a different pH value is given accordingly. Historically, the technology came forth from a close cooperation with Piet Bergveld of the Twente University.

Glass-Free and Durable Probes

In contrast to glass pH electrodes, ISFET pH electrodes are robust and reliable in demanding environments. This makes them well suited for many food, bioreactor, and pharmaceutical applications. Even in education and laboratories, where in principal glass pH electrodes can be used, the ISFET pH measurement technology offers a much more durable and reliable solution.


Specifically, for applications in agriculture and for meat quality measurements in the meat industry, we offer robust probes with a steel tip that can be equipped with a handle for additional grip. The meter is dust and splash waterproof and has a rubber boot for shock absorbance. All openings are well sealed.

Dry Storage

ISFET pH electrodes do not require wet storage, in contrast to glass pH electrodes. This makes them well suited for applications like water quality measurements in stream beds and tidal areas, where the water level changes in time and the probe will occasionally be above the water level.

High Quality and Food Safety

Quality and shelf life of food products are of paramount importance, and pH is an important indicator for quality in products like meat, fish and dairy goods. The robustness of non-glass, in combination with the unique small size of our probes (down to 2mm in diameter with a separate reference), allows pH sampling without loss of produce.

All Sentron pH probes are made of high quality food safe materials such as PEEK, ABS and PVC. The probes have a polymer body snap-on type connector and there are neither moving parts nor screw thread that can be damaged. The position of the ISFET and reference electrode has been designed to be clog and pollution resistant. In the event debris has accumulated on the sensor it can be easily cleaned with water and a brush.

Small Sample Sizes

In many pharmaceutical and biochemical processes only small volume samples are available. Enabling measurements in mini-cuvettes and test tubes, we offer pH probes for liquid volumes as small as 20µL.

Intuitive User Interface

The user-friendly interface allows users to quickly access the meter’s advanced features and settings. During menu navigation, pH and temperature data remain visible. The advanced data acquisition capabilities of the SI600 permit extensive storage of measured data points and continuous data logging at a user defined time interval. Stored and logged data points can be transmitted to a PC through the USB port and with suitable software the meter’s momentary pH value and temperature can be queried.

Standard pH Products