Specific Electrode Meters
Ion specific meters are millivolt meters that interface with ion selective electrodes (ISE). The meters take the potential generated by the electrode and convert it into units of concentration. A pH meter that also measures millivolts can be used to interface with an ISE. Most ISEs are combination electrodes that have the reference electrode built into the body of the ISE, however some ISEs require a separate reference electrode. In this case, the pH/mV meter must have a pin-connector to attach to the reference electrode.
To order the proper ion specific meters, the user must know certain specifications. First is the concentration the ISEs are to measure. Also the number of ISEs to be attached to the meter. Other important options for these instruments are other measurements they can perform, typically of temperature, pH and oxidation-reduction potential (ORP), also known as redox. These instruments can have some controller functionality such as set limits, regulator, P/PI/PID as well as control relay output.
Mounting options for ion specific meters are quite varied. They can be handheld meters, larger portable meters with wheels or handles for carrying, and modular for interfacing with sensors of different input ranges. Other styles commonly available are specially designed for lab or benchtop use and others for field or in-situ applications. Some of these meters are designed to be mounted in a panel.
Displays for the instruments can be analog meters, a numeric or alphanumeric digital display or video, a CRT or LCD style. Another option is to have no local display at all and have the data gathered by another instrument. Likewise, the user controls can also be analog or digital or can be operated through a host computer. To simplify the instruments, preprogrammed devices without user controls are available.
Electrical output options are the standard voltage and current outputs as well as an analog frequency or a change in state of switches or an alarm. Serial and parallel ports can help connect these instruments to a host computer.
Some features available for many ion specific meters include battery power for greater portability and built-in signal processing filters. Built-in calibration ability and self-test functions are also available, as are event triggering and ratings for extreme environments.
