Single or Multiparameter Instrumentation Hanna Instruments offers both single parameter and multiparameter instruments in order to meet a variety of testing requirements. Using Single Parameter Hanna single parameter instruments offer simple, accurate and efficient measurement focused on, as the name implies, a single parameter. They are well suited to applications where one parameter must be tested quickly and easily. They are generally simple to operate and can be used by non-technical users. Using Multiparameter The advantage of Hanna multiparameter instruments is that a user can choose a single meter with the ability to measure multiple parameters . Multiparameter instruments offer different operating solutions well suited to meeting multiple requirements and are available in two primary configurations: 1. Multiparameter meters that can measure two or three parameters, but only one parameter at a time. 2. Multiparameter meters that offer two or three parameters measured simultaneously—useful on experimental and research applications where the influence between the parameters is an important factor. Multiple inputs provide the capability for simultaneous measurement. pH Measurement Input Hanna meters generally come in two different electrode connection types: BNC or DIN. BNC Connector: A BNC (Bayonet Neil-Concelman) is a common connector used for coaxial cable devices. A BNC connection is generally used for combined electrodes and half-cell electrodes that require a separate reference probe and separate reference input. DIN Connector: A DIN (Deutches Institut für Normung) is a circular connector. It is used to connect amplified pH electrodes. Electrodes utilizing a DIN connector feature a built-in temperature sensor. Temperature Input Temperature has an effect on pH measurements. As such, temperature compensation is required for accurate measurements. Temperature compensation can be obtained in three ways: 1. A separate probe specifically for measuring temperature 2. A probe with a temperature sensor built-in 3. Manual adjustment for temperature If a temperature input is not present, many instruments still offer the ability to manually adjust the temperature according to an external temperature reference. pH Temperature Compensation pH readings must be temperature compensated in order to obtain accurate results. The source of temperature measurement can be from a temperature sensor or from a trimmer that is manually adjusted. In either case, the instrument is adjusting the pH reading to compensate for changes in the pH sensor. Compensation in pH provides the actual pH at the temperature of measurement. mV Reading Hanna meters with an mV feature offer the ability to read the mV potential from a pH, ORP, or ISE electrode. The relative mV allows the user to offset the mV difference generated from sensors or references. pH/ISE Calibration pH calibration should be performed daily or every time a new lot of readings is started. Any errors during calibration will affect all the readings until a new calibration is performed. Errors during the calibration process can be eliminated if standard calibration procedures are followed. Hanna recommends the following standard calibration procedure: 1. Clean and activate the electrode before the calibration. 2. Use fresh pH buffers and standards. 3. Rinse the electrode with purified water during the calibration process to avoid buffer contamination then rinse in buffer or standard. 4. Wait for a stable reading before the calibration point is confirmed. 5. Compensate the pH reading for temperature. Calibration is a key component to ensuring accurate readings during pH measurement. With this in mind, Hanna supplies each of our pH instruments with a starter package of calibration solutions. pH CAL Check™ Many instruments feature Hanna’s exclusive pH CAL Check technology. CAL Check is a diagnostics system that ensures accurate pH readings every time. By alerting users to potential problems during the calibration process, the CAL Check system eliminates erroneous readings due to dirty or faulty pH electrodes or contaminated pH buffer solutions during calibration. During the calibration process, users are prompted with a step-bystep, on-screen tutorial. After calibration, the electrode is evaluated and the condition and response time is provided. Depending upon meter, this may be a graphic of GLP information. Calibration Errors Instruments utilizing Hanna’s CAL Check technology can evaluate an electrode during calibration and store a history of parameters that describe the quality of electrode to be compared from one calibration to another. During calibration, a very small degradation of these parameters is normal and can be expected. A big change in the parameters signifies an error in the calibration procedure, such as a dirty electrode. pH Buffer Contamination pH buffers can be contaminated during the calibration procedure by numerous factors such as introducing a contaminated probe, using old buffers, or by reusing buffers. These factors may cause inaccurate calibration and subsequent measurements. Hanna’s CAL Check can often detect issues during calibration, giving warning messages to inform users about the identified issue. Introduction 2 pH 2.2 | www.hannainst.com introduction
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