Analog vs. digital sensors: What’s the difference in pH measuring devices? 

By Thomas Chirdo, Liquid Analysis Product Marketing Manager at Endress+Hauser

When selecting pH measuring devices for chemical, pharmaceutical or industrial applications, understanding the difference between analog vs. digital sensors is essential. Analog sensors transmit raw millivolt signals that are vulnerable to electrical interference and require manual calibration.

Digital sensors, on the other hand, convert the signal internally and transmit it into a robust digital format, often with built-in diagnostics, temperature compensation and calibration memory. This makes digital sensors more reliable, easier to maintain and better suited for integration with modern laboratory and industrial systems. 

Let’s look at Endress+Hauser’s Memosens digital sensors, for example. They feature non-contact inductive signal and power transmission, eliminating issues caused by moisture or corrosion. Models like Memosens CPS11E, CPS61E and CPF81E offer extended calibration data storage, predictive maintenance capabilities and compatibility with hazardous area certifications (ATEX, IECEx, CSA C/US).

These sensors are designed for demanding environments, from bioreactors and CIP/SIP processes to mining and wastewater treatment. 

pH probes measure hydrogen ion activity using a glass-sensitive membrane or ISFET electrode and a reference electrode. The voltage difference between them corresponds to the pH level. However, this measurement is sensitive to: 

• Temperature fluctuations 

• Flow rate and pressure 

• Sensor fouling or drying out

Digital sensors help mitigate these issues with temperature compensation algorithms and chemically stable reference gels. For example, Memosens CPS61E is designed for biotech and pharmaceutical applications, including enzyme production and culture growth. Its special glass membrane and reference system make it resistant to CIP/SIP and is autoclavable up to 140°C, ensuring long-term stability and reproducible measurements.

In addition, certified for biocompatibility and compliant with FDA and USP Class VI standards, Memosens CPS61E protects product quality while maximizing yield. 

Pharmaceutical labs are increasingly adopting digital pH measuring devices that support smart features and IIoT integration. Memosens sensors offer: 

• Extended calibration and process data storage 

• Predictive maintenance capabilities 

• Autoclavable, hygienic sensor designs 

• Compatibility with analog systems via converters like the CYM17 

Sensors like Memosens CPS77E and Memosens CPS97E are optimized for sterile environments and high-precision applications. Their ability to store calibration data and perform lab-based calibrations streamlines workflows and improves measurement reliability across batch processes. 

Choosing between analog vs digital sensors depends on your process conditions and operational goals. Key considerations include: 

• Temperature, pressure and flow rate – harsh conditions favor digital sensors 

• Media characteristics

• Maintenance accessibility – sensors should be easy to clean and calibrate 

• Redundancy needs – critical processes benefit from multiple sensors with voting logic 

• Integration requirements – digital sensors simplify connectivity with lab and process systems

For mobile or spot-check applications, Memosens CPL51E is a flexible solution. It’s ideal for grab sample analysis, field verification of online loops or pH measurement at process points without permanent instrumentation. With automatic temperature compensation and fast response time, even in cold, ion-weak water, Memosens CPL51E supports both lab and field use while maintaining data integrity through tamper-proof calibration history.

Proper maintenance extends the life and accuracy of pH measuring devices. Best practices include: 

• Keep sensors wetted when not in use (use 3.0 molar KCl + buffer)

• Clean regularly with non-lanalin soap and warm water or mild acid for scaling

• Avoid abrasive tools that can damage the electrode – soft bristled toothbrush only

• Calibrate with temperature stabilization to ensure reliable readings

• Use offline calibration for digital sensors to improve accuracy and reduce downtime

Digital sensors like Memosens simplify maintenance with features such as internal diagnostics, long calibration intervals and chemically stable reference gels. Software tools like Memobase Plus further streamline sensor management by automatically storing and documenting calibration and process data. 

In the debate of analog vs digital sensors, digital options are increasingly favored for their durability, smart features and compatibility with modern lab infrastructure. By understanding how pH probes work and following best practices for installation and maintenance, labs and plants can ensure reliable chemical analysis and avoid the common pitfalls that plague pH measurement.

Whether you're working in a pharmaceutical lab, a chemical processing plant, a mining operation or conducting field sampling, choosing the right pH measuring devices is a strategic decision that affects both performance and productivity.