New Development: BERU high temperature sensor (HTS) for monitoring turbo chargers, exhaust gas recirculation systems, Diesel particle filters and DeNOx catalytic converters
High measuring accuracy, fast response time, mechanical stability, flexible installation options: With the new closed high temperature sensor (HTS) BERU is making use of its expertise gained from glow plug technology.
Ludwigsburg, May 26, 2009 - Sensors play a central role in modern cars. Vehicles contain an average of around 100 of these sensing devices as standard. Why? Increasingly more stringent exhaust gas limits values and ever-increasing demands in terms of safety, accident protection and driving pleasure. Special temperature sensors are required in order to protect components such as turbo chargers. They sit directly within the flow of exhaust gas, measure its temperature, and direct the data to the engine control unit for analysis and processing.
The new high temperature sensor (HTS) from BERU is now delivering a more accurate, faster temperature sensor, that offers more long-term stability, and which is structurally much more versatile. “Our aim was to develop a closed sensor to meet our partners’ demands for short response times,” said Dipl. Ing. Ulrich Schneider, Sensors Product Manager at BERU, at the firm’s head office in Ludwigsburg, as he explained one of the specifications.
Other development aims included:
- a measuring range of minus 40 to plus 950 degrees Celsius,
- a standard characteristic line as per DIN IEC 751,
- plug and play capability,
- extremely long service life,
- high resistance to exhaust gas by careful materials selection and with special design,
- flexible fitting position,
- flexible dimensions and geometry to meet customer requirements,
- an “one size fits all solution” for the greatest possible flexibility in production and manufacturing technology.
HTS sensor elements in platinum: measuring accuracy and extremely durable
BERU uses an RTD element (resistance temperature detector) for the actual sensor, made of platinum that is specially adapted to these specifications for development. In theory an NTC is suitable for recording high temperatures, i.e. a measurement resistance with negative temperature coefficients, a thermocouple or a platinum shunt resistor. BERU has opted for optimum combination of measurement range, signal yield and stability and thus for a thin-layer platinum shunt resistor. A significant advantage of such a platinum sensor is its standardized characteristic line and its OBD capacity over all temperature ranges.
Conventional platinum sensors consist of a platinum thin layer applied to an aluminum oxide substrate, which in turn is protected from damage by a thin cover of glass. On platinum shunt resistors processes are induced at temperatures of around 800 degrees Celsius which can change their characteristic line, among other things. On the new platinum shunt resistor BERU has therefore replaced this layer of glazing with an insulating ceramic layer, which is ap-plied densely by means of special processes. This structure prevents the sensor element from undergoing chemical aging.
Closed sensor design: long-term stable and flexible to manufacture
The new BERU HTS is a closed high temperature sensor, the structure of which is based on very many elements from BERU’s glow plug design. The shunt resistor is well protected inside a closed protective cap filled with magnesium oxide. As with all connecting metallic components, this consists of INCONEL 601 chrome nickel special steel, which is outstandingly suitable for the application due to its exceptional resistance to temperature and sulfur. This steel has already proved itself very successfully in BERU glow plugs, which are subject to similar conditions to which the temperature sensor in the exhaust gas are exposed. As with glow plugs, the magnesium oxide is condensed by crimping for improved strength. Laser welding is used to join the protective cap to the mounting sleeve.
There are many advantages to the design of the sensor: For example HTS sensors from BERU have a rapid response time and can be installed in almost any fitting position. Schneider, who is a sensor specialist, explained: “Open constructions almost always have to be installed vertically downwards, so that no condensate water can collect inside them which could result in the sensor corroding. And with open sensors there is always the risk that the tip will collect carbon deposits, which can have a negative effect on the sensor’s response time. This type of clogging does not happen with closed HTSs.” The dimensions and geometry of the new BERU HTS sensor are extremely flexible. Depending on customer requirements, it is possible to achieve immersion depths of 25 to 70 millimeters as well as bending angles of 90 to 180 degrees. The HTS is being manufactured on two fully-automatic lines at BERU’s headquarters in Ludwigsburg.
BERU is meeting increased customer demands for an expansion of the testing facilities of new and innovative sensor products - necessary from the point of view of quality - and at the same time reducing development times, at its Research and Development Centre (R&D) in Ludwigsburg. The specialist in Ignition Technology, Diesel Cold-Start Technology, Electronics and Sensors offers a wide variety of services to its partners: from the development and selection of material, covering high-performance prototype manufacturing up to 100-percent testing on dedicated test benches, and the electromagnetic compatibility specification (EMC) at the BERU R&D Center.
BERU has developed a separate new test and inspection procedure for the HTS. In what is known as the “hot shake” test the sensors are mounted on a vibrating table, heated to 900 degrees Celsius for 144 hours, and at the same time subjected to different types of vibration, such as could occur within the engine. Another test procedure involves an alternating temperature test, used to simulate the different temperature ratios encountered while a vehicle is driving. The sensors move onto a pneumatic table 12,000 times inside a furnace heated to 950 degrees, while, outside, the temperature reaches around 150 degrees.
BERU sensors: Proficiency from a single source
“We understand ourselves to be a development partner for sensors to the international automotive industry and automotive suppliers,” explained Schneider. “It means that customers benefit from more than 30 years of experience in the sensor sector and from our enormous manufacturing expertise in the fields of metal processing and plastics engineering.” With its current range of products BERU has increasingly specialized in innovative sensor solutions for the power train and exhaust system. These include:
- Temperature sensors for applications in Diesel particle filters, oxidation catalytic converters, SCR systems, NOx storage cats and turbo chargers such as the new BERU HTS,
- Movement sensors such as speed sensors, distance and angle sensors,
- SMART sensors with intelligent electronics such as the radiator identification sensor (RIS), developed by BERU.
