pH and ORP Series Sensors 871PH

871ph series ph and orp sensors and accessories

The 871PH Series are rebuildable, precision, electrochemical sensors, and when used in conjunction with 871PH accessories, are suitable for pH and ORP measurement applications.


The 871PH Series sensors are used with Foxboro 870ITPH Intelligent Transmitters, 875PH and 876PH Intelligent Analyzers and transmitters, 870PH Analog Transmitters, and 873PH and 873DPX Electrochemical Analyzers. The Model 871PH Sensor includes a robust and continuously reusable sensor body with a field replaceable measuring electrode, and field replaceable reference junction and electrolyte. Numerous options and accessories are offered to enhance the performance of these transmitters.


Unique pH glass - exceptionally stable, remains fast and accurate after severe temperature cycling (121°C/250°F). Proven high stability, high accuracy, and long life. Easy-to-use body design simplifies installation, calibration, maintenance, and replacement. More reliable measurements permit tighter process control. Longer life plus easy mounting reduces maintenance costs.


Measurement of pH by these sensors is accomplished by immersing a glass or metal electrode, with a reference electrode, into a process solution. The glass or metal electrode produces an electrical potential proportional to the logarithm  if the hydrogen ion activity. The reference electrode completes the circuit and provides a stable reference for the glass or metal electrode. These two electrodes constitute an electrolytic cell having a millivolt output that is proportional to the pH of the solution. ORP is related to the logarithm of the ratio of oxidation activity to reduction activity, just as pH is related to the logarithm of the hydrogen ion activity. A solution that contains an excess of oxidizing agent has a positive ORP while one containing an excess of reducing agent has a negative ORP. Typical ORP applications include treatment of chromate and cyanide wastes produced by plating, chemical, and metal treatment plants. ORP monitoring enables industry to determine reaction end points and to meet today's stringent environmental requirements.


Many new measuring electrodes, reference junctions, options, and accessories have been added to the 871PH sensor family. These include: High temperature electrode featuring unique DolpHin™ Series high temperature glass. Patented double junction reference with integral Nafion ion barrier. Variopin Quick cable connector. Optional selections for high temperature cable and O-ring material. A ptfe collar, which improves self-cleaning, and also minimizes coating buildup.


This multi-purpose sensor assembly is suitable for most process pH and ORP measurement applications. Its flexibility is further enhanced when used with a variety of mounting accessories. The sensor accepts a variety of glass pH, metallic pH, and ORP electrodes. The unit is not affected by normally encountered chemical solutions and is capable of withstanding continuous operation in a wide range of process pressures and temperatures.


The sensor assembly is available in either a Ryton or CPVC body. The Ryton body can be used in most normally encountered chemical solutions, and is the preferred material where organic chemicals are present. The CPVC body is used in applications involving hypochlorites or peroxides (e.g., bleach).


Each measuring electrode is available in either a Ryton body or ptfe body. Ryton measuring electrode body should be used when using a Ryton sensor body. The ptfe electrode body is used with a CPVC sensor body. Glass pH electrodes offer the best performance in most solutions and inherently provide the most accurate measurement. The glass electrode is available in one of three types: spherical, flat, and domed. Antimony, platinum, and gold electrodes are also offered for specific applications. See below for description and recommended use for each type.


If you require further information on this product or would like a quotation, please contact dp-flow on:

sales +44(0)1865 600245