Maintenance-Free pH Sensor for Harsh Environments

The Yokogawa FU24 is a new ’four in one’ pH sensor designed to offer virtually maintenance-free operation and long sensor lifetime – especially in harsh applications involving severe temperature and pressure fluctuations. The new sensor incorporates a patented Yokogawa-designed bellows system, which automatically compensates for the effect of pressure fluctuations.

Such pressure variations can be highly detrimental to sensor operation, as they can initiate a pumping effect resulting from the expansion and shrinkage of the gel or liquid inside the sensor. The outcome is that the process liquid will start to ingress into the sensor and the reference voltage - and hence the pH measurement - will start to drift.

In the FU24 sensor, pressure fluctuations are automatically compensated by the built-in bellows up to 10 bar, making the sensor virtually insensitive to pressure variations. A positive overpressure maintained by the tension in the bellows generates a steady flow out of the sensor.