Engine management barometric pressure sensors

Figure 1 Bosch SMP480 barometric pressure sensor (Source: Bosch Media)

The new Bosch SMP480 barometric pressure sensor is extraordinarily small. It takes up just one-quarter of the space of its predecessor. This makes it easier than ever to include it in the electronic control units used in automotive technology. This is the first time the Stuttgart-based automotive supplier has released a pressure sensor in its SMP range that uses a 12-bit digital interface to provide pressure and temperature data, instead of producing an analog measurement signal. This digital barometer’s pressure signal tolerance over its lifetime is less than 1.0 kPa – the best accuracy currently available in the market. The SMP480, which features a ten-pin premold SMD housing and is RoHS-compliant, is already being delivered in large quantities.

Pressure sensors make cars more eco-friendly
Barometric pressure sensors are a key component in engine management for diesel and gasoline engines. They are designed to measure the current ambient pressure accurately and with low drift. Atmospheric pressure is a function of height above sea level as well as of weather conditions. The engine management system uses the sensor measurement data to ensure the optimum air-fuel mixture, irrespective of whether the vehicle is traveling along a coastal road or a road up in the mountains. The benefit of this constant rebalancing of the mixture ratio is that it reduces fuel consumption as well as emissions of CO2 and other pollutants.

Silicon sensor membrane
The core of the SMP480 is its sensor element. This is made up of a monocrystalline silicon membrane – manufactured using the advanced porous silicon membrane (APSM) process – which hermetically seals a reference vacuum. Four strain gages are implanted in the membrane in a bridge circuit. Changes caused by atmospheric pressure in the curvature of the membrane, even those measuring just a few thousandths of a millimeter, are converted into an electrical signal. Signal conditioning and A-D conversion are performed by an ASIC adjacent to the sensor element within the housing.

A success story with over 1.6 billion MEMS sensors

Bosch sets the pace in MEMS (micro-electro-mechanical systems) technology. The company has manufactured over 1.6 billion MEMS sensors since production began in 1995. This makes Bosch the global market leader in MEMS sensors. Its product portfolio comprises pressure sensors, acceleration sensors, yaw-rate sensors, mass flow sensors, torque sensors, and microphones for a variety of automotive and consumer electronics applications. Additional information on the Bosch sensor program can be accessed at www.bosch-sensors.com.

Technical data – SMP480 (sample of typical values)
Measurement range 40 kPa to 115 kPa
Pressure tolerance ≤ 1,0 kPa
Pressure tolerance ≤ 3 K in the range 25 bis 85 °C
Interface SPI, 12-bit precision
for pressure and temperature
Operating voltage 3,3 V(DC)
Power consumption ≤ 8,0 mA
Permissible ambient
-40 to +130 °C
Housing Premold 10-pin
6.9 mm x 5.7 mm x 2.4 mm (l x b x h)

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