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 HI12300 uses general purpose (GP) glass, spherical bulb, polyetherimide (PEI) body, single ceramic frit, and double junction.
General Purpose Glass Formulation
General Purpose (GP) glass, as the name implies, is a standard glass formulation that is used for general use. A pH electrode with GP glass will have a resistance of 100 megaohms at 25°C and is suited for measuring pH of samples that are at ambient temperatures. The HI1230B is suitable to use with samples that measure from 0 to 70°C.
The built-in microchip stores sensor type, serial number and calibration information including date, time, offset, slope, probe condition and buffers used. This information is automatically retrieved by edge®once the electrode is plugged in. The ability to transfer information allows for hot swapping of probes without having to recalibrate. All pH measurements are performed within the electrode and transferred digitally to the meter. This overcomes any noise issues associated with the traditional high impedance analog measuring system. Electrical noise can be generated from a built in temperature sensor and while working in a humid environment.
The spherical bulb is for general purpose use. Other tip shapes include conic for penetration and flat tip for surface measurements.
The body of the HI12300 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.
Double Junction Reference
A double junction electrode has an internal compartment surrounding the reference wire. Silver ions are present in the electrolyte of the internal compartment, which houses the Ag/AgCl reference wire; the electrolyte outside this compartment is silver free. The double junction design means that virtually no silver from the electrode enters the sample. This design allows measurement in applications where silver ions in the sample are undesirable or silver precipitates on the junction are likely to form.
Built-In Temperature Sensor
HI12300 features a built-in thermistor temperature sensor that is in the tip of the indicating pH electrode. A thermistor temperature sensor provides for a high accuracy temperature reading and should be as close as possible to the indicating pH electrode in order to compensate for the effect that temperature has on the membrane potential. By having an accurate reading it is possible to provide an accurate temperature compensated reading.