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Hach/GLI pHD™ Differential pH and ORP Sensors


pHD™ Differential Electrode Measurement Technique.
This field-proven technique uses three electrodes instead of the two normally used in conventional pH sensors. Process and reference electrodes measure the pH differentially with respect to a third ground electrode. The end result is unsurpassed measurement accuracy, reduced reference junction potential, and elimination of sensor ground loops. These sensors provide greater reliability, resulting in less downtime and maintenance.

Replaceable Salt Bridge/ Protector.
The unique, replaceable salt bridge holds an extraordinary volume of buffer to extend the working life of the sensor by protecting the reference electrode from harsh process conditions. The salt bridge simply threads onto the end of the sensor if replacement is needed.

Built-in Encapsulated Preamp.
Encapsulated construction protects the sensor’s built-in preamp from moisture and humidity, ensuring reliable sensor operation. This preamp produces a strong signal, enabling the sensor to be located up to 3000 ft. (914 m) from the analyzer.

Durable PEEK® Body Material.
The pHD™ Differential pH and ORP sensors feature a durable PEEK® body for chemical compatibility with most process solutions. For less aggressive solutions, GLI offers a Ryton® sensor in a convertible style for pH and ORP measurement.

Convertible Body Style
The convertible style sensor features 1-inch NPT threads on both ends of its body to mount:
• Into standard 1 inch pipe tee.
• Into GLI adapter pipe for union mounting with standard 1-1/2 inch pipe tee.
• Onto end of pipe for immersion into a vessel.
Insertion Body Style
The insertion style sensor is similar, but has no threads on the electrode end. When used with a GLI ball valve hardware assembly, the sensor can be inserted into/retracted from the process without stopping the flow.
Sanitary Body Style
The sanitary style sensor has an integral 2-inch flange, special cap, and EPDM compound gasket for use with GLI 2-inch sanitary tees and mounting hardware.
New and Retrofit Hardware Mounting
Hardware for new and existing installations is offered in a variety of materials for all sensor body styles.

  • Specs
  • Ordering
  • Accessories
  • Engineering
  • Dimensions


1. Most pH applications fall in the 2.5-12.5 pH range. A GLI pHD™ Differential pH sensor with the wide-range glass process electrode performs exceptionally well in this range. Some industrial applications require accurate measurement and control below 2 or above 12 pH. In these special cases, please contact GLI for further details.

2. For best ORP measuring results in solutions containing zinc, cyanide, cadmium or nickel, GLI recommends using the pHD™ ORP sensor equipped with an optional gold electrode.

To learn more, contact IIS at 1-877-215-9090 or 732-815-9090.

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Industrial Instrumentation Services, Inc.
1400 Rahway Avenue, Avenel, NJ 07001-2214
P: 732-815-9090 F: 732-815-9092
Toll Free: 877-215-9090