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 HI4430B uses a gold pin, PEI body, single ceramic junction and gel electrolyte.
Gold Sensing Pin
The HI4430B ORP sensor is made with gold. An ORP sensor must be chemically inert; it cannot be oxidized 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: platinum and gold. Pure platinum and pure gold are both used in the construction of ORP sensors. The gold sensor signal is carried through the electrode body, and together with the reference signal is conducted to the measurement meter.
PEI Body
The body of the HI4430B is composed of polyetherimide (PEI) resin. The PEI body is suitable for a wide range of applications and excels in field measurements due to its durability. The shielding around the spherical glass tip minimizes breakage due to accidental bumping or dropping of the electrode. The PEI plastic is a high quality plastic that is chemically resistant to many aggressive chemicals.
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.
BNC Connector
The HI4430B 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 type 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.
