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ORAKEL pH sensors measure the online pH of any aqueous solution

pH Sensor

Key Features

  • Up to 5 years continuous operation
  • Stable and reliable
  • Suitable for all potable and process waters
  • Suitable for very low conductivity waters
  • Integral temperature compensation


The range of ORAKEL pH sensors measure the online pH of any aqueous solution. They are combination glass electrodes with integral reference, automatic temperature compensation, solid polymeric junction (pH4), which use no reagents, are extremely stable, and have reduced maintenance and reduced whole life costs.

What makes it unique

The pH4 electrode is patented and has a large area electrochemically active solid polymer junction. This innovative design makes the electrode more responsive and with a longer life than ordinary electrodes (typically 3-5 years). Although they command a higher price in the market place these sensors are more than cost effective with their longer life and considerably lower maintenance requirements, typically only needing calibration once per two or three months.

pH4 is particularly sensitive to difficult pH4 applications such as very low ionic strength waters or chemically corrosive applications. pH1 – pH3 are less expensive, more traditional combination electrodes.




Combined reference, and measuring electrode

Reference Type

Patented electrochemically active solid polymer junction (pH4)

Ag/AgCl gel filled (pH1-pH3)

pH Range




Pressure range


Long Term Stability (drift)

<0.01 pH/Hour


<0.01 pH


pH Glass <200 MOhm

Solid State

<200 KOhm

Response Time

95% of step pH2 to pH12 <5s

Response Time

95% of step pH2 to pH12 <5s

Temperature Range

0-100°C (pH4)

0-80°C (pH1-pH3)

Wetted Surface

pH Glass – Red Polymer – PVDF Body – Viton 0 rings


Low Noise Coaxial + 4 wires

Cable length – 6m

Shelf Life

12 Months



Estimated life

36 months application dependent (pH4)

12-18 months application dependent (pH1-pH3)


1 year (pH4)

3 months (pH1-pH3)


Installation Options

The ORAKEL PH sensors can be installed in a variety of auxiliary flow cells and self-cleaning devices.



Anywhere you have a requirement to measure pH is a suitable application for our pH sensors. One area the sensors excel is in the measurement of pH in very low conductivity or ultra clean water. They are also particularly suited to working in sites where reliability and ease of use are most important.

Typical applications include:

  • Remote Sites
  • Food Preparation
  • Potable Water
  • Cooling Towers
  • Paper Mills
  • Chemically Challenging Applications

Quick Selection Guide

pH 1

pH 2

pH 3

pH 4

Potable Water    
Waste Water      

Mounting Options

Single Open Flow Cell  
Dual Open Flow Cell  
Triple Open Flow Cell  
Closed Flow Cell  
Autoclean (Flow Cell)      
Autoclean Immersion (Dip)      
Autoclean Insertion (In Pipe)      
At Line Tee  
Welding Stub  


Standard Cable Length 1m 6m 6m 6m
Max. Temperature 80°C 80°C 80°C 100°C
Back/Front Thread N/A ¾” NPT (Front only) ¾” NPT (Front & Back) ¾” BSP (Front & Back)
Water Proof Cable (Submersible    


The ORAKEL can  come equipped to automatically clean itself at user defined intervals with all the benefits of no operator intervention for 6 months. The Autoflush is particularly useful in food preparation, pulp and paper, and many applications where there is likely to be a build up of solids in the sample. Autoflush is available for at line, and in line versions including dip and screw in autoclean pipe version.
See Autoflush for more information.

Learn More

Find the most up to date product information and available downloads

Datasheets – EN
MMS D017 – ORAKEL control unit

Watch our Predictive Data Monitoring Video here

Read More

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