Maintaining a car is necessary since this is a way to avoid expensive repairing services. You should not forget about various liquids, like oil and other fluids. There are various resources for drivers, like Halfords or bestfordriver where you can get the best differential fluid for different types of vehicles. The automotive industry went a long way and today we have modern, easy-to-use vehicles that can get us from the point “A” to the point “B” without any problems.
Various systems evolve to something we have today – reliable and easy to maintain solutions. Pressure sensors belong to those systems.
Sensors in your car
Sensors provide an engine control unit with the necessary information. The control unit can change various parameters to make your trip safer and prolong engine life. The most important parameters are manifold absolute pressure (MAP) and barometric absolute pressure (BAP).
- MAP shows the mass of air flowing in the car engine. The data can use to modify the sparks working regime to make it optimal
- The BAP sensor data is used for altitude compensation
Manufacturers use silicon piezoresistive sensors. Such sensors can be also used to measure the pressure in the exhaust gas recirculation system or in the fuel injection system
There are three types of such sensors:
- Analog signal sensors
- Discrete-analog signal sensors
- Digital signal sensors
Analog signal sensors
The first design of the sensors included analog signal conditioning circuits. The manufacturing process was quite complex since such sensors had the film resistor network which was adjusted via the laser trimming technology. The network was used with a ceramic substrate. This assembly was inserted into a PC board.
The manufacturing process was later improved and the sensor became more compact. The manufacturers started using hybrid technology, they also started producing the ceramic substrate with printed thick film resistors.
Some manufacturer went even further and they decided to combine analog circuits with thin film resistors on the same chip. The sensors became even smaller and more accurate.
These sensors used discrete adjustments. However, signal processing still remained in the analog form. The “next stage”, which included trimming and calibration, was done in the discrete form (in other words, it had steps). However, this technology had a serious flaw – the discrete method of processing may reduce the accuracy and resolution of the sensor and decrease the authority range.
However, some manufacturers preferred this technology and they not only got accurate results but also went further implementing the CMOS technology. Such sensors had two chips – the first stored the calibration data and the second had the sensor and the amplifier combined via the bipolar technology.
This kind of sensors uses digital signal processing technology. The data gathered by sensors is processed by a digital signal processing algorithm. Further compensations are achieved via various operations and then the signal is converted to analog.
Such solutions are built using multiple chips and it makes them quite expensive. However, manufacturers could decrease the price of the product over time. Such sensors are monolithic, so one “piece” can do everything, unlike analog sensors, where a separate module was used. The calibration of digital sensors is performed during the last stage of the auto manufacturing process.