Combined Intelligence
New transmitter and an innovative sensor makes liquid analysis easier

The process analysis and instrumentation team used to be a separate department, but times have changed. Today, you rarely find departments that have the luxury of focusing exclusively on specialized tasks such as pH instrumentation. The new realities have forced manufacturers to develop user-friendly platforms which essentially encapsulate the knowledge of a whole team of
experts. This is the approach taken by Endress+Hauser Conducta when the company developed its new Liquiline transmitter generation which is used in combination with Memosens technology.

Anyone who has worked in a lab knows the problem. A “simple” pH measurement can turn into a nightmare simply because the workbench is not grounded. It is not that easy to get an undistorted signal to the sensor. There can be a lot of hidden problems along the path to the sensor. Moisture and contamination can distort the signal. Cable length and cable characteristics can affect signal quality. Measurement in the lab is anything but easy, and online analysis during the ongoing process is even more challenging. This has led many companies to look at ways of achieving undistorted signal transmission. However, the efforts were often limited to addressing the symptoms. The Memosens sensor from Endress +Hauser Conducta, which was introduced last year, is a real breakthrough. It solves the electrical and mechanical problems, and it eliminates problems with high ohm measurements in moist, contaminated environments. The sensor opens the door to a fundamentally new approach to measurement technology.

A sensor with a brain
A chip inside the sensor head converts the measurement value into digital signals. The inductive, non-contact connector guarantees an undistorted signal path to the transmitter. The electrode is a defined, closed system which can be calibrated as a separate entity. The cable is only used for power and signal transmission and has no influence on measurement accuracy. A warning is raised if there is a problem with the connection between the sensor and the transducer, for example if the cable is disconnected. A conventional sensor would provide false data. The electrical isolation of the transducer simplifies wiring requirements and enhances electromagnetic compatibility. The cable is attached to the sensor via a bayonet connector. This prevents accidental removal of the process connector when the cable is detached.
However, built-in “intelligence” enables the Memosens to do a lot more. The ability to store calibration data is a huge advantage. The sensors can be pre-calibrated in the lab under optimal conditions, and they can then be quickly swapped on the system. pH glass electrodes with Memosens functionality, non-glass sensors and oxygen sensors are available which have the new technology. Conductivity and turbidity sensors are expected to be introduced in the near future.
Always well informed
However, digital technology in the transducer is also needed to fully exploit all of the functions of Memosens technology. The new Liquiline transmitter platform, which Endress+Hauser Conducta introduced worldwide in September 2005, is the perfect complement to these sensors according to Wolfgang Babel, General Manager of the company. He emphasized that “the platform is totally focused on the user. User-friendly operation eliminates many potential sources of error, and in doing so it enhances operational reliability and productivity.” Liquiline allows users to read sensor information such as serial numbers and calibration data as well as process information including sensor operating time, number of calibration operations, maximum operating temperature and operating time under extreme conditions (e.g. a defined temperature limit). The design of Liquiline complies with the international safety standard IEC 61508 (SIL 2). All of the information presented by the transmitter during initial installation, ongoing operation and maintenance is in clear text. The menu is clearly structured and self-explanatory. Users are guided step by step, and a user-friendly push and turn button called the Navigator makes it easy to select menu items. Help is available at the press of a key. Soft keys (programmable keys) provide direct access to key functions. Clear text messages are presented on a user-friendly 240 x 160 pixel display. When the user exits from the operator menu, the results of the current measurement are displayed on 28 millimeter digits which are clearly legible even from an acute angle. Diagnostic messages provide timely warning of changes and errors. A flashing red LED also signals limit violations and fault conditions. A second output can be used as a low-cost option for an additional measurement value, or warnings can be forwarded to the control station. The Liquiline exterior features a clean design, and the interior is also well laid out. The main module, which has a communications and power output, and the sensor module are mounted on a DIN rail. Modular design gives the system great flexibility. Users only need to swap individual modules to adapt the system to different measurement parameters and fieldbus systems. The modules automatically make contact when they are inserted, and this feature along with self-detection of the parameter software gives the user the benefit of true plug-and-play functionality. Liquiline is designed to work with all of the popular fieldbus systems. A variety of language settings are available on the transmitter including Chinese. The housing is designed for field use. The unit can be pole mounted or installed in a control cabinet. In addition to a plastic housing which is designed for universal use, a hygienic stainless housing is available as an option. The transmitter is suitable for Ex applications. It is has Atex II (1)2G EEx ib (ia)IIC T6/II 3D approval and offers intrinsic safety in compliance with FM IS Cl.I Div 1. User administration and log book entries in conformance with 21 CFR 11 are also included. All types of sensors including ISFET, glass electrode and conductive and inductive conductivity sensors can be attached to the transmitter. Initially the Liquiline is available as a two-wire version for pH/Redox, conductivity and dissolved oxygen analysis. A four-wire version, which will have a color display, is currently under development.