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HI-3131B Glass Body Refillable ORP Electrode Pt BNC

HI-3131B Glass Body Refillable ORP Electrode Pt BNC

Hanna HI-3131B Glass Body Refillable ORP Electrode Pt BNC

HI-3131B Glass Body Refillable ORP Electrode Pt BNC

Ideal for general laboratory use
6 months warranty
In Stock
£188.90 (exc. VAT) £226.68 (inc. VAT)

The HI-3131B is a glass body, refillable, single junction ORP electrode with a BNC connector. This electrode has a single ceramic junction as part of the reference cell and a platinum ORP sensing pin.

This design consideration is ideal for laboratories and general purpose ORP measurements, as well as for use as an indicating electrode in ORP titrations.

  • Refillable Electrode
  • Single Ceramic Junction
  • Platinum Pin
  • HI-3131B Glass Body Refillable ORP Electrode Pt BNC information

    Hanna's extended description

    Hanna Instruments offers a wide variety of ORP electrodes that are designed for many different applications. The type of material used for the sensing pin, type of glass used for body material, type of junction, type of reference and electrolyte used are just some of the design considerations.

    The HI-3131B uses a platinum pin, glass body, single ceramic junction and is refillable with 3.5M KCl + AgCl.

    Platinum Sensing Pin

    The HI-3131B ORP sensor is made with platinum. An ORP sensor must be chemically inert; it cannot be oxidised or reduced itself. It must also have the proper surface characteristics to promote rapid electron exchange, a property known as high exchange current density. Two noble metals have proven to work well for this purpose: pure platinum and pure gold are both used in the construction of ORP sensors. The platinum sensor is often preferred because it is mechanically simpler and safer to produce. Platinum can be welded to glass and has the same thermal coefficient. The platinum sensor signal is carried through the electrode body, and together with the reference signal is conducted to the measurement meter.

    Glass Body

    The glass body is ideal for laboratory use. The glass is resistant to many harsh chemicals and is easily cleaned. The glass body also allows for a fast transfer of heat to the internal reference electrolyte. The mV generated by the reference cell is temperature dependent. The faster the equilibrium - the steadier the reference potential.

    Single Ceramic Junction

    The outer junction of an electrode, also known as a salt bridge, is necessary component of the electrical circuit. The movement of ions must flow through the junction for a steady reading. The outer reference has a single ceramic frit. The ceramic is a porous material that is easily fused with the glass body and has a similar expansion coefficient. A single ceramic junction has a flow rate of 15-20 μL/hour. Other junction types are available with higher flow rates and made with different materials.


    The HI-3131B is a refillable probe. Since it is a single junction ORP electrode the fill solution is the HI-7071 3.5M KCl + AgCl. If using a refillable ORP electrode, the fill cap should be removed prior to measurement. Removing the cap creates positive head pressure in the reference cell allowing for higher flow rate of electrolyte through the outer junction. A higher flow rate will result in a faster and more stable reading.

    BNC Connector

    The HI-3131B uses a BNC connector. This type of connector is universal in that it can be used on any pH meter that has the female BNC probe input. Other types of connectors include DIN, screw type, T-type, and 3.5mm to name a few. These types of connectors tend to be proprietary for a particular type of meter and are not interchangeable.

    BNC Connection – BNC is one of the most commonly used connector types in pH meters and electrodes. Compatible with any meter or electrode that uses BNC connectors.

    All electrodes and probes have 6 months warranty. See our warranty and returns policy explained.


    Specifications list


    Reference Single, Ag/AgCl
    Junction/Flow Rate ceramic, single / 15-20 µL/h
    Electrolyte KCl 3.5M + AgCl
    Max Pressure 0.1 bar
    Range ORP: ±2000 mV; -5 to 70°C
    Tip Shape Platinum Pin
    Temperature Sensor No
    Amplifier No
    Body Material Glass
    Cable Coaxial; 1 m (3.3')
    Connection BNC

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