A New Breed of Automotive Sensors Hit the Road

Is it any wonder when self-driving cars are being registered for use on California highways that the number of new sensors targeting automotive applications is exploding? Growth of sensor products and sensor technology advances are not just heading in a driverless direction, but also are essential to creating numerous new safety and infotainment offerings for OEM and Tier-1 suppliers.

Today’s vehicles are highly complex electronic control systems that rely on a diverse range of sensors to collect and deliver critical data encompassing automotive performance, safety, comfort, and convenience. Sensor cost is still a significant factor in the selection criteria, with an eye to lower price tags if large production volumes are to be achieved. In most cases sensor use completely supports a given vehicle function; in some cases, however, they are the differentiating factor that enable a consumer wish-list feature in newly designed vehicles.

This article will look at a representative sampling of new sensors, their applications, and how their use will impact the rapidly changing automotive industry.

From battery management to stability control

BMW just announced that it is using the ams AG AS8510, an integrated automotive sensor interface, to ensure extremely accurate battery voltage and current measurements in its “i3” series of electric vehicles (EVs). The i3 model currently in volume production includes an AS8510 in the battery sensor. The critical battery management system (BMS) monitors voltage and current of the 400 V li-ion battery powering the cars’ electric motors and also ensures the functional safety of a vehicle’s battery systems. Accurate measurements provided by the AS8510 (Figure 1) enable the BMS to make a highly precise calculation of a li-ion battery’s State of Charge (SOC). Drivers benefit from an accurate estimation of the vehicle’s range before the battery is completely discharged.

The sensor system in the BMS is able to measure current to an accuracy of just ±0.5 percent and voltage to an accuracy of better than ±0.1 percent over the full operating temperature range of the AS8510 (-40°C to +125°C) and over its lifetime. Features of the AS8510 include a zero-offset architecture, low noise, high linearity, multi-channel architecture, and low drift.


Figure 1: The ams AS8510 is ideal for shunt-based batteries. BMW just announced its integration in the i3 electric car series.

The AS8510 provides integrated data acquisition front-ends, which include two independent 16-bit sigma-delta ADCs. Measuring current across a shunt resistor in one channel over a range from a few milliamps up to 1 kA, it provides a digital output via a serial peripheral interface. Through the second channel it can capture three different voltage sources simultaneously with current samples. The AS8510 is fully compliant with the AEC-Q100 standard. The device supports the functional safety compliance efforts of car manufacturers in line with the requirements of the ISO26262 standard.

The Allegro Microsystems A1468 optimized Hall-Effect sensing IC provides an attractive solution for digital ring-magnet sensing or, when coupled with a magnet, ferromagnetic target sensing in three-wire applications. The device (Figure 2) is ideally suited to obtaining speed and duty cycle information in ring-magnet-based speed, position, and timing applications, such as in speedometers. The small device package can be easily assembled into applications for use in conjunction with a wide variety of target shapes and sizes. It incorporates dual Hall-Effect elements with a 2.2 mm spacing and signal processing that switches in response to differential magnetic signals created by ring-magnet poles.


Figure 2: The Allegro A1468 provides a solution for digital ring-magnet sensing or ferromagnetic-target sensing in three-wire applications such as speedometers.

A sophisticated digital circuit reduces system offsets, to calibrate the gain for air gap, independent switch points, and for zero-speed operation through a peak-detecting algorithm. The signal optimization occurs at power-on by combining offset and gain adjust, and it is maintained throughout operation with a running-mode calibration that provides immunity to such environmental effects as micro-oscillations of the target or sudden air-gap changes.

A part worth considering for use in climate control, defogging control, and in systems to prevent condensation is the Amphenol Advanced Sensors’ ChipCap 2-SIP CC2D23, a Single In-Line Package type of ChipCap that features an already installed V-Core capacitor for easy and convenient application. It is an advanced and cost-effective humidity and temperature sensor with a capacitive polymer chip and CMOS integrated circuit with EEPROM integrated into one embedded system.

The device is individually calibrated and tested and performs ±2 percent from 20 percent to 80 percent RH (±3 percent over entire humidity range), and is both simple and ready to use without further calibration or temperature compensation. Features, in addition to the calibration and temperature compensation, include digital (I²C) output, precision, and accuracy (±2 percent RH, ±0.3°C, 14-bit), free-operating voltage (min 2.3 V to max 5.5 V), and low current consumption.

Targeted to automotive applications with high stability and reliability requirements, such as Electronic Stability Control (ESC), engine vibration measurement, suspension adjustment, and roll-over prevention, the Murata Electronics SCA610-E23H1A Single Axis Accelerometer with analog interface (Figure 3) consists of a silicon bulk micro-machined sensing element chip and a signal-conditioning ASIC. The chips are mounted on a pre-molded package and wire bonded to contacts.


Figure 3: Functional block diagram of the SCA610-E23H1A accelerometer. Murata accelerometers are based on the company’s proprietary 3D MEMS technology.

The sensing element and the measuring ASIC are assembled in a dual-in-line or dual-in-flat-line plastic package with pins for surface-mount and re-flow soldering. They are environmentally protected with silicone gel, resulting in excellent performance and reliability in a humid environment and at temperature cycling. They maintain performance even in harsh and vibrating environments and include enhanced failure detection: digitally activated self-test, calibration-memory parity or sum check, and continuous-connection failure detection.

In summary, automotive is one of the fastest-changing sensor-market segments. Sensors range from safety and driver assist to motor control and over-the-top communications applications; nearly every system within the vehicle is being upgraded based on sensor advances and sensor integration. We’ve provided a brief look at just a few of the more recent automotive sensors available to design engineers.

For more information on these parts, use the links provided to access product information pages on the Digi-Key website.