Hanna Instruments offers a wide variety of pH electrodes that are designed for many different applications. The type of glass used for sensing pH, bulb shape, body material, type of junction, type of reference and electrolyte used are just some of the design considerations.
The FC214D uses high temperature (HT) glass, spherical bulb, titanium body, and cloth junction with gel electrolyte.
High Temperature Glass Formulation
The measurement of pH at very high temperatures is detrimental to the sensitive glass bulb and will shorten the life of it. A pH electrode with general purpose (GP) glass will have a resistance of 100 megaohms at 25℃ while the resistance of HT glass is around 400 megaohms at 25℃. As the FC214D is used at elevated temperatures, such as in the wort or mash, the resistance decreases and approaches the resistance of GP glass. The FC214D is suitable to use with samples that measure from 0 to 80℃.
The spherical bulb is for general purpose use. Other tip shapes include conic for penetration and flat tip for surface measurements.
A pH measurement is a very sensitive voltage measurement that is susceptible to interference from electrical noise and humidity. To overcome these issues a titanium body serves as a matching pin. A matching pin is a differential measurement technique used to eliminate electrical noise in the measurement system. The titanium body, being made of metal, is virtually unbreakable and offers additional protection from accidental breakage.
Every pH electrode has a junction. They can be made from a variety of material including ceramic, PTFE, and a fiber wick. The fiber wick is also known as a cloth junction and is often used on electrodes with gelled electrolytes. The advantage of the cloth junction is that it can be extracted from the probe exposing a fresh surface. This is very important since one of the major contributors to unstable measurements is a clogged junction. This is likely to occur when measuring the pH of mash that has a high solids content. Having the ability to pull out a small portion (.125″) of the junction will clear any clogging resulting in an increased life of the pH electrode.
The FC214D uses a DIN connector. This type of connector is proprietary to the meter they are to be used with. The FC214D is the replacement electrode for the HI99151. Other type of connectors include BNC, screw type, T-type, and 3.5mm.