Foxboro 871A pH and OPR Sensor

871A Analytical Sensor

The Foxboro 871A series is a robust, high-performance line of pH and ORP (oxidation-reduction potential) sensors engineered for use in demanding industrial process environments. Known for its chemical resistance, mechanical durability, and low maintenance requirements, the 871A is a trusted choice in applications where stable, long-term measurement is essential. Built with a PVDF body and flat-surface electrode, the sensor resists chemical attack, coating, and fouling—especially in flowing liquids or slurries. Its modular design allows it to be easily integrated into a wide variety of process systems, from chemical plants and wastewater treatment to food & beverage, pharmaceuticals, and pulp & paper operations. The sensor is available in both standard analog models and Smart Sensor versions, which offer advanced diagnostics, configuration memory, and enhanced compatibility with HART-capable analyzers such as the Foxboro 875PH, 876PH, and 870ITPH.

Ideal for:

• Water/ Wastewater
• Chemical
• Pulp and Paper
• Food and Beverage
• Pharmaceutical
• Metals
• Neutralization

Features:

• Flat-surface electrode
• PVDF body
• Built in 100 ohm RTD
• Automatic temperature compensation
• Optional smart sensor options
• Compatible with:
  • 875PH
  • 876PH
  • 873PH
  • 973DPX
  • 870PH
  • 870ITPH
• 1″ NPT connections
• 3 m cable standard, 15 m available
• pH range of 2-12
• ORP range of +/- 2000 mV
• 6.9 bar pressure rating
• –5°C to 100°C operating range

Document Downloads:

• 871A-Data Sheet