Multicolour multi-talent

Dr. Dirk Steinmüller

The Stratos Pro units from Knick allow users to measure pH, redox potential (ORP), conductivity, toroidal conductivity and oxygen concentration values even in very rugged environments. The series consists of intrinsically safe two-wire models for use in hazardous areas (Zone 1) with the sensor installed in Zone 0 as well as two-wire models for safe areas. There will additionally be mains-operated four-wire models that are suitable for use in Zone 2. All devices support Hart communication and are certified for standard asset management systems from leading process control system suppliers.

Stratos Pro units, which are equipped with a widescreen display, feature a completely new operating concept. Since, according to a Namur study, operator errors lead to more downtime in modern transmitters than hardware defects, malfunctions or measuring errors, Knick’s main development objective was user-friendly, intuitive operation. Therefore, the Stratos Pro display shows high-resolution, self-explanatory pictograms instead of pixel graphic elements which are sometimes hard to recognise. Long text displays are scrolled horizontally in a large, easily readable font, because ticker lines are steadier and easier to understand than text with line breaks. The functional multi-colour backlight is a particular eye-catcher. The Stratos Pro display can switch between six different colours, thereby clearly indicating operating modes. The standard Measuring mode, for example, has a white backlight, while displays in Information mode appear in green and the Diagnostics menu is backlit in turquoise. The Alarm status was assigned an especially conspicuous, deep shade of red and is additionally indicated by flashing display values. Incorrect inputs or wrong pass numbers thus result in a red, flashing display, which considerably reduces operator errors. The units also support a Hold function, which is important for process devices: if a unit is integrated into a process control system (either for monitoring purposes or actively in a control process), the data output must not provide incorrect values because of interference with the device. In such cases, e.g. during calibration, the unit automatically switches to Hold mode. The Stratos Pro display then changes to an orange screen that makes sure this operating mode is visible even from a distance. In order to optically enhance asset management messages, notifications relevant for predictive diagnostics (e.g. concerning maintenance requirements, pre-alarms and sensor wear) appear with a magenta backlight.

The multi-colour backlight has been implemented in the two-wire model for the first time, even though this connection/supply method must manage with the least electric power. The Stratos Pro series also has further features, especially in the two-wire models. The units provide two digital inputs which can be used, for instance, to activate Hold or switch parameter sets externally. Moreover, the transmitters feature an analogue current input which allows users to loop through temperature or pres-sure signals. They are equipped with a second current output for a second measured value. Stratos Pro four-wire models, on the other hand, are supplied with the VariPower wide range power supply unit which has been used with other devices for years. It allows the same product to be purchased – with the same order number – for any mains supply from 20 to 253 V(AC/DC), thereby ensuring safe operation worldwide even with an unsteady power supply.

All standard analogue sensors can be used with Stratos Pro. However, the series also steps right into the digital age concerning sensors. The devices can be optionally operated with contact-based digital systems such as ISM or contact-free, induction-coupled digital sensors which provide the great advantage of perfect electrical isolation. Stratos Pro supports both the InduCon standard and Memosens technology. The InduCon system in particular combines the benefits of contact-free data transfer with high-performance functions for predictive diagnostics, e.g. remaining sensor lifetime, wear index, calibration history with an adaptable calibration timer and continuous sensor monitoring on the glass and reference side. The connector system, which is recognisable by its characteristic red or green status LEDs on the sensor head, is therefore now suitable for use in a wider range of applications. Since InduCon sensors can be employed with all Stratos Pro devices, InduCon solutions will become more attractive, especially for cost-sensitive applications. The main objective in designing Stratos Pro was maximum flexibility for users regarding the choice of sensors. Inductive conductivity sensors from different manufacturers, for instance, have different operating points and therefore require individual input signals and operating frequencies. Thanks to a special circuit technology, the two and four-wire models enable operation with virtually all standard sensors for the very first time.

Stratos Pro is equipped with a reinforced, corrosion-resistant plastic housing with a robust design. The almost completely smooth front does not feature any protruding operating elements that could be subject to severe mechanical stress. Specially sealed, high-quality operating keys render glued-on front foils, which would need to act as a seal, unnecessary. Thanks to these features, the high IP 67 degree of protection is not affected by accidents involving sharp tools etc. Safe operation is possible between -20 and 65 °C. The Stratos Pro display window is connected to the plastic housing during the moulding process. Consisting of hardened 3 mm safety glass, it is scratch and UV resistant. All electronic components are encapsulated in the door module and there are no exposed circuit boards. The large lower housing section can be installed separately. All electrical connections are carried out via plug terminals in the door unit, so that the wiring in the lower housing can be retained if the door unit is exchanged. Stratos Pro units are provided with a door contact switch, which creates a log entry in case of un- authorised access. This is especially essential in pharmaceutical processes requiring Audit Trails according to 21 CFR Part 11.

cpp 450

Knick

SPS/IPC/DRIVES 2008