Digital progress: new generation of sensors replaces analogue technology

Citation

(2009), "Digital progress: new generation of sensors replaces analogue technology", Sensor Review, Vol. 29 No. 4. https://doi.org/10.1108/sr.2009.08729daf.003

Digital progress: new generation of sensors replaces analogue technology

Article Type: Mini features From: Sensor Review, Volume 29, Issue 4

Auto lighting and electronics company Hella has developed a new generation of sensors (Figure 2) for contactless measurement. The first application is the recording of throttle-body position which will go into production in autumn of 2009.

The technology, based on the recent single edge nibble transmission (SENT) protocol for data transmission in cars, means analogue vehicle sensors can be replaced easily and economically with modern digital solutions.

Figure 2 Contactless measurement sensors from Hellas based on the recent SENT protocol

SENT engineers use the term “one nibble” to refer to a data quantity of 4 bit. In the SENT protocol, it is transmitted with each pulse. The pulses are evaluated only on the basis of the falling edges, hence “Single Edge”.

Hella’s Contactless Inductive Position Sensor (CIPOS^®) are a series of contactless inductive position sensors. The advantages of these sensors for travel and angle measurement are particularly relevant in the engine compartment, such as in throttle bodies. Here, high temperatures and vibrations mean that an insensitive measuring system is necessary.

Currently, sensors are fitted at numerous locations in cars. For reasons of costs, connections to digital data-bus systems are not worth it in every case. For example, the throttle-body sensor is often connected directly to the control unit, and the data transmission takes place in analogue form. Owing to the multiple conversions from digital to analogue signals and vice versa, there is a whole series of interference effects, the minimisation and detection of which is costly.

Digital transmission of data via the SENT protocol and the sensors from Hella is much more reliable. A big advantage is the compact and simple design of the corresponding applications. One cable with three single wires is sufficient for the supply of the sensor and the data transmission to the control unit. In addition, two signals can run over the data wires, which means that costs for additional cables can be saved. In contrast to other technical approaches, screened or twisted cables are not necessary, because the signals of the SENT protocol are very insensitive to interference.

The technology allows easy and economical replacement of analogue transmission. In electronic sensors, the sensor information – the throttle-body angle, for example – is usually converted into a digital value and processed. An interface then turns this into the analogue signal, which the receiver at the end of the cable in turn converts into a digital one.

In the case of digital transmission via SENT, the data remain completely digital – from conversion in the CIPOS^® sensor to processing in the control unit. Different measures ensure the reliability of the data and, unlike analogue transmission, signals on digital transmission routes cannot be falsified without detection. A big advantage of the solution from Hella is also the high electromagnetic compatibility.

Hella will go into production with the digitally controlled throttle-body sensor in the Autumn of 2009 and, looking ahead see a further application being the recording of steering torque.